Rozprawy doktorskie na temat „Fly Ash-lime”

Acid mine drainage (AMD) is one of the largest problems facing the mining of base metals in Canada today. It results in the leaching of toxic heavy metals from waste rocks and tailings into the environment. Solidification/stabilization is a process whereby hazardous wastes are chemically stabilized and their handling properties improved. The objective of the project was to stabilize two tailings obtained from base metal mines in Quebec by adding varying proportions of lime and fly ash to them. The fixing capabilities of the two additives were tested by a modified Toxicity Characteristic Leaching Procedure (TCLP) test after 1, 14 and 35 days of curing. Mineralogical changes were monitored by the x-ray diffraction (XRD) analysis of 6 selected samples.
Results indicated the capability of lime-fly ash binders in the immobilization of heavy metals. XRD analysis showed the formation of gypsum and the gradual decline in pyrite content in most of the samples. The mineral ettringite was not detected, probably due to the relatively low pH of the samples and a deficiency in reactive aluminum. Hence, the results suggest the existence of other phases, possibly amorphous calcium silicates, which were responsible for the reduction in leachability.

A series of microanalytical (Optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy ) and geotechnical (standard compaction , hydraulic conductivity, one-dimensional consolidation, and direct shear) tests used for analysing the effectiveness of lime and fly ash on soil stabilisation from a chemical/elemental and geotechnical viewpoints. The geo-chemical analysis was revealed the creation of chemical components required for the chemical reaction, thereby improving the soil’s geotechnical performance.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE EXCELENCIA ACADEMICA
Este estudo apresenta o comportamento de misturas de areia e solo argiloso com teores variados de cinza volante, proveniente do processo de queima de carvão mineral no Complexo Termelétrico Jorge Lacerda, localizado no município Capivari de Baixo, no estado de Santa Catarina. O objetivo da presente pesquisa consiste em avaliar a aplicabilidade do uso de misturas solo-cinza e solocinza- cal em obras geotécnicas, como camadas de aterros sanitários, solos de fundação e estabilização de taludes. Foram realizados ensaios de caracterização física, química e mecânica (ensaio de compactação e ensaio de cisalhamento direto). Os ensaios de cisalhamento direto foram realizados em amostras de solo argiloso compactadas na umidade ótima e no peso específico seco máximo correspondente, com teores de cinza volante de 15 por cento e 30 por cento em relação ao peso seco do solo. Já os ensaios em amostras de areia foram realizados para uma densidade relativa de 50 por cento e umidade ótima de 10 por cento, com teores de cinza volante de 15, 30 e 40 por cento em relação ao peso seco do solo. Para as misturas solo-cinza-cal, adicionou-se 3 por cento de cal em substituição ao peso seco da cinza. Foi analisada a influência do tipo de solo, teor de cinza, adição de cal e tempo de cura (0, 30, 100, 125 e 140 dias) para as misturas, sendo a cura adotada somente para as misturas com areia. Os resultados mostraram-se mais satisfatórios para as misturas com solo argiloso, sendo a adição de cal mais eficiente para a mistura com menor teor de cinza. Na ausência de cal, o melhor comportamento obtido foi para a mistura com 15 por cento de cinza. Quanto às misturas com areia e sem cal, os resultados foram inferiores à areia; já no caso das misturas areia-cinza-cal, não foi possível definir um padrão do comportamento com relação ao tempo de cura, pois ainda que tenha havido um aumento da coesão a determinados dias, este ganho veio acompanhado de uma redução no ângulo de atrito, fazendo com que a areia mantivesse um comportamento melhor. Contudo, o teor de 27 por cento de cinza, sob 140 dias de cura, proporcionou ao solo um aumento de ambos os parâmetros, sendo, portanto, o teor ótimo a ser utilizado. Dessa forma, ainda que o emprego da cinza volante em misturas com o solo argiloso tenha se mostrado mais satisfatório, este material também pode ser utilizado em misturas com areia, desde que submetido a elevados períodos de cura e que contenham uma porcentagem de cinza em torno do teor ótimo encontrado, o que viabiliza o emprego positivo deste material em aplicações geotécnicas, possibilitando uma destinação ambientalmente correta deste resíduo e dando um fim mais nobre a este material.
This study presents the behavior of sand and clay soil mixtures with different contents of fly ash, which comes from the coal burning process in Thermoelectric Complex Jorge Lacerda, located in the city of Capivari de Baixo, in Santa Catarina. The aim of this research is to assess the applicability of using soil-ash and soil-ash-lime mixtures in geotechnical works, like landfill layers, foundation soils and slope stabilization. Physical, chemical and mechanical (compaction test and direct shear test) were performed. Direct shear tests were performed on clay soil samples compacted at the optimum moisture content and the corresponding maximum dry specific gravity, with fly ash contents of 15 and 30 per cent, related to the dry weight of soil. Tests on sandy soil samples were performed at the relative density of 50 per cent and optimum humidity of 10 per cent, with fly ash contents of 15, 30 and 40 per cent related to the dry weight of soil. For soil-ash-lime mixtures, it was added 3 per cent of lime to replace the dry weight of ash. It was studied the influence of different parameters: soil type, ash content, lime addition and curing time (0, 30, 100, 125 and 140 days) for the mixtures. Curing process was adopted only for sandy soil mixtures. Results were more suitable for clay soil mixtures, and lime addition was more efficient for the mixture with the lowest ash content, related to 12 per cent. In the absence of lime, the best performance was obtained for the mixture with 15 per cent of ash. For sandy soil mixtures and without lime, the results were inferior to sand; and in the case of soil-ash-lime mixtures, it was not possible to define a pattern of behavior to the curing time, because although there has been an increase in cohesion certain days, this gain was followed by a reduction in friction angle, which has maintained the best performance of sand. However, the ash content of 27 per cent, at 140 days of curing, caused an increase of both parameters, what means that this ash content is the optimum content to be used. Thus, although the use of fly ash in mixtures with clay soil has been more satisfactory, this material can also be used in mixtures with sandy soil, since it contains an ash content around the optimum content found, and since it has been submitted to elevated curing periods, what enables the positive employment of this material in geotechnical applications, providing an environmentally correct disposal of this waste and giving it a noblest destination.

Expansive soils are one of the most serious problems which the foundation engineer faces. Several attempts are being made to control the swell-shrink behavior of these soils. One of the most effective and economical methods is to use chemical additives. Fly ash and desulphogypsum, both of which are by-products of coal burning thermal power plants, are accumulating in large quantities all over the world and pose serious environmental problems. In this study, the expansive soil was stabilized using the fly ash and desulphogypsum obtained from Ç
ayirhan Thermal Power Plant. Fly ash and desulphogypsum were added to the expansive soil from 0 to 30 percent. Lime was used to see how efficient fly ash and desulphogypsum on expansive soil stabilization were, and was added to the expansive soil from 0 to 8 percent. The properties obtained were chemical composition, grain size distribution, consistency limits, swelling percentage, and rate of swell. Fly ash, desulphogypsum, and lime added samples were cured for 7 days and 28 days, after which they were subjected to free swell tests. Swelling percentage decreased and rate of swell increased with increasing stabilizer percentage. Curing resulted in further reduction in swelling percentage and further increase in rate of swell. 25 percent and 30 percent fly ash and desulphogypsum additions reduced the swelling percentage to levels comparable to lime stabilization.

Slurry walls have been widely used for more than 25 years to control the migration of contaminants in the subsurface. In the USA, vertical barriers are mostly constructed of soil-bentonite using the slurry trench method of construction. In this method, sodium bentonite is mixed with water to form a viscous slurry that is pumped into a trench during excavation to maintain the trench stability. The stable trench is then backfilled with a mixture of soil and slurry having a consistency of high slump concrete. These barriers have been designed primarily for low permeability, generally less than 10&minus
9 m/s. Some investigations have pointed toward improved performance using admixtures that would provide low permeability. In this study, Soma thermal power plant fly ash, granulated blast furnace slag, lime, and steel slag are used as admixture to improve the performance of slurry walls. Permeability, compressive strength, slump, compressibility properties of the mixtures were found and checked for the minimum requirements. According to the findings of this study, granulated blast furnace slag (GGBS), fly ash and steel slag can be used at certain percentages and curing periods as additive in cement-bentonite barrier wall construction. Permeability of specimens having fly ash decreases by increasing fly ash content. Mixtures having 50 % of GGBS type I with 5 % of lime and 9% bentonite content gave acceptable results in 28 days of curing time. Specimens including 50 % of GGBS type II with 5 % of lime and 9% bentonite content gave the higher permeability value in 28 days of curing time with respect to GGBS type I. In addition, most of the mixtures prepared by steel slag gave the acceptable permeability values in 28 days of curing period. Unconfined compressive strength of all mixtures increase by increasing curing time. Cc, Cr, Cv, kcon values were found from consolidation test results. Permeability values found from consolidation tests are 10 times to 100 times higher than flexible wall k results for the same effective stress of 150 kPa. Generally, mv values are decreasing with increasing curing time. As mv decreases, D increases.

O emprego de resíduos da indústria como materiais alternativos na Engenharia vem sendo tópico recorrente em pesquisas de desenvolvimento de novos materiais, devido a uma maior consciência da opinião pública quanto ao impacto ambiental oriundo da produção industrial. Buscando colaborar com esta discussão, esta pesquisa procurou inserir dois resíduos (cinza volante e cal de carbureto), gerados na região metropolitana de Porto Alegre, como alternativa de solução em Engenharia. Analisando-se a microestrutura da cinza volante, observa-se que ela é formada por esferas ocas e plerosferas (esferas ocas preenchidas por esferas menores). Foi estudado o ganho de resistência da mistura promovido pela moagem da cinza volante em um moinho de bolas cerâmicas, visando uma potencialização da reatividade do material. A fim de possibilitar a utilização destes resíduos, é necessário um estudo do seu comportamento mecânico decorrente da cimentação proporcionada pela mistura e compactação destes materiais. A presente pesquisa busca fornecer subsídios para que seja possível determinar o seu comportamento, através do uso da relação porosidade (η)/teor volumétrico de cal (LV) obtidas a partir da identificação e quantificação das variáveis mais importantes no controle da resistência da mistura dos dois resíduos, com e sem o processo de moagem da cinza, levando a formulação de equações para previsão da resistência à compressão simples do material cimentado para cinza volante com diferentes tempos de moagem e cura acelerada. Para isso, foram realizados ensaios de compressão simples em corpos de prova com 5, 10 e 15% de cal, com peso específico aparente seco de 11, 12 e 13 kN/m3, curados por 7 dias, com umidade de 18% para os tempos de moagem 0, 2 e 6h nas temperaturas 23 e 40°C, e 0 e 6h a 60°C. Os resultados apontam que o aumento do teor de cal gerou ganhos de resistência para as maiores temperaturas de cura; a diminuição da porosidade proporcionou um ganho de resistência para todas as combinações; o aumento da temperatura foi importante no ganho de resistência entre 23oC e 40oC; a moagem da cinza por 2h promoveu ganhos significativos de resistência em relação à não moída, porém, para 6h de moagem os ganhos não foram significativos para as temperaturas de cura de 23oC e 60oC. A relação η/LV, ajustada por um expoente [η/(Lv)0,07], mostrou-se adequada na formulação de equações na previsão da resistência do material cimentado para todas as temperaturas e tempos de moagem estudados. Além disso, a existência de relações únicas e distintas no controle da resistência à compressão simples em função da porosidade, teor volumétrico de cal, temperatura de cura e tempo de moagem, mostraram-se úteis para formulações de dosagem. Os resultados foram submetidos à análise de variância que comprovou que todos os fatores controláveis escolhidos para o experimento são significativos, assim como todas suas interações.
The use of industry by-products as alternative materials in Engineering has been a recurring topic of research in development of new materials, mainly, due to a larger public conscience regarding the environmental impact of industrial production of waste. Aiming to contribute on this discussion, this research sought to introduce two by-products (fly ash and carbide lime), produced on the metropolitan area of Porto Alegre, as an alternative Engineering solution. Analyzing the microstructure of the fly ash, it is observed that it is composed by void spheres and plerospheres (void spheres filed with smaller ones). Having that in mind, it was studied the admix strength gain promoted by the grinding of de fly ash on a ceramic ball mill, aiming an enhancement of the reactivity of the material. In order to enable the use of these byproducts, it is necessary the study of its mechanical behavior due to the cementation provided by the mixture and compaction of these materials. The current research seeks to provide subsides in order to determine its behavior, through the use of the ratio porosity (η)/ volumetric lime content (LV), obtained from the identification and quantification of the most important variables on the control of the strength of the admixes of both by-products, with or without the process of fly ash grinding. This means, the formulation of equations for the simple compressive strength forecast of the cemented material for the fly ash with different grinding times and accelerated curing temperature. In order to do so, it were realized simple compression tests with 5, 10 and 15% of lime, with a specific dry unit weight of 11, 12 and 13 kN/m3, cured for 7 days, with water content of 18% for the grinding times of 0, 2 and 6h to the curing temperatures of 23 and 40oC, and 0 and 6h to 60oC. The results show that, the increase of lime content provided strength gains for the higher temperatures; the decrease of porosity generated strength gain to all the combinations; the increase in curing temperature was important on the strength gain between 23oC and 40oC; the grinding of fly ash for 2h promoted significant strength gains when compared to the not ground samples, however, for 6h of grinding the strength gain wasn’t significant for the 23oC and 60oC curing temperatures. The η/LV ratio, adjusted by an exponent [η/(LV)0,07], presented itself adequate for the formulation of the equations for the forecast of the strength gain of the cemented material to all the studied temperatures and grinding times. Besides that, the existence of unique and distinct relationships on the control of the simple compression strength depending on the porosity, volumetric lime content, curing temperature and grinding time, have been shown useful for the dosage formulation. The results were submitted to variance analysis, which demonstrated that all the factors chosen on the experiment were significant, as all their interactions.

A utilização de cinza volante na composição de material cimentício o torna mais sustentável, além de conferir à matriz hidratada características peculiares que melhoram o desempenho frente à ação de diferentes agentes deletérios. A principal desvantagem da utilização de pozolana no sistema cimentício é a maior susceptibilidade à carbonatação. A maior taxa de neutralização da solução aquosa dos poros é devida ao teor remanescente menor de portlandita na matriz. O conhecimento das características da cinza volante que influenciam a interação com a cal, é necessário para subsidiar medidas preventivas com relação ao consumo de portlandita. A presente pesquisa objetiva verificar a eficiência da adição de cal hidratada em concreto executado com cimento pozolânico como forma de reduzir a susceptibilidade à carbonatação. As etapas realizadas para cumprir o objetivo abrangem: a caracterização da cinza volante, com ênfase na determinação do teor de fase vítrea; a cinética de reação em sistema de cinza volante e hidróxido de cálcio; a evolução da hidratação, e a decorrente variação microestrutural. Nos sistemas cimentícios de concretos cujas composições são 100% de cimento ou 50% de cimento e 50% cinza volante, com e sem a adição de 20% de cal hidratada, foi caracterizado a microestrutura da camada de cobrimento e o seu desempenho frente à ação do anidrido carbônico, em ensaio acelerado. Na cinza volante estudada, o teor de fase vítrea foi de 57%, e o consumo máximo por atividade pozolânica, função da área específica BET, foi de 0,69 gramas de Ca(OH)2/grama de fase vítrea de cinza volante. No cimento portland pozolânico, este consumo é menor devido à estrutura formada pela hidratação do cimento. A adição de cal hidratada à pasta de cimento e cinza volante, além de aumentar o consumo de cal por atividade pozolânica, restabeleceu, parcialmente, o teor remanescente de portlandita na matriz. A interação da cinza volante com a cal hidratada não interfere no volume total de vazios da matriz hidratada, porém, refina a microestrutura, aumentando o volume de mesoporos. A carbonatação, em concretos com mesma resistência à compressão de 55 MPa, atingiu maior profundidade quando executado com cimento pozolânico. A adição de cal hidratada não foi eficiente em reduzir a susceptibilidade à carbonatação acelerada.
The use of fly ash in the composition of the cementitious material makes it more sustainable, besides conferring to the hydrated matrix peculiar characteristics which improve its performance with relation to the action of different deleterious agents. The main disadvantage of pozzolan utilization in cementious systems is its susceptibility to carbonation. The greatest neutralization rate of the aqueous solution of the cement pore is, generally, attributed to the smallest amount of portlandite remaining in the matrix. It is necessary to widen knowledge about the characteristics of the fly ash which influence the interaction with calcium hydroxide in order to promote preventive measures with regard to portlandite consumption. This current research aims at verifying the efficiency of hydrated lime addition to concrete by using pozzolanic cement as a way of reducing its susceptibility to carbonation. The steps employed to attain this objective include: fly ash characterization with an emphasis on glass content; fly ash and calcium hydroxide systems kinetics; hydration evolution; and the consequent microstructure variation. In cementious systems of concrete whose composition is either 100% cement or 50% cement and 50% fly ash _ with or without 20% addition of hydrated lime _ it was characterized the microstructure of covercrete and its performance with regard to the interaction with carbon dioxide in accelerated testing. In the studied fly ash, glass content was 57% and the maximum consumption per pozzolanic activity, which is function of BET specific surface area, was 0.69 g of Ca(OH)2/g of glass content in the fly ash. As far as pozzolanic Portland cement is concerned, this consumption is smaller due to the structure formed by the cement hydration. The addition of hydrated lime to the cement paste and fly ash, besides increasing the consumption of lime per pozzolanic activity, partially, reestablished the remaining content of portlandite in the matrix. The interaction of the fly ash with the hydrated lime does not interfere in the total volume of void spaces in the hydrated matrix; however, it refines the microstructure by increasing the volume of mesopores. Carbonation in concrete with the same compressive strength of 55 MPa reached its deepest point when performed in pozzolanic cement. The addition of hydrated lime was not efficient at reducing susceptibility to accelerated carbonation.

The Portland Cement Association commissioned a research project at Brigham Young University to compare selected laboratory durability tests available for assessing stabilized aggregate base materials. The laboratory research associated with this project involved two granular base materials, three stabilizers at three concentration levels each, and three durability tests in a full-factorial experimental design. The granular base materials consisted of an aggregate-reclaimed asphalt pavement blend obtained from Interstate 84 (I-84) and a crushed limestone obtained from U.S. Highway 91 (US-91), while the three stabilizer types included Class C fly ash, lime-fly ash, and Type I/II Portland cement. Specimens were tested for durability using the freeze-thaw test, the vacuum saturation test, and the tube suction test. Analyses of the test results indicated that the unconfined compressive strength (UCS) and retained UCS were higher for specimens tested in freeze-thaw cycling than the corresponding values associated with vacuum saturation testing. This observation suggests that the vacuum saturation test is more severe than the freeze-thaw test for materials similar to those evaluated in this research. The analyses also indicated that the I-84 material retained more strength during freeze-thaw cycling and vacuum saturation and exhibited lower final dielectric values during tube suction testing than the US-91 material. Although the I-84 material performed better than the US-91 material, the I-84 material required higher stabilizer concentrations to reach the target 7-day UCS values specified in this research. After freeze-thaw testing, the Class C fly-treated specimens were significantly stronger than both lime-fly ash- and cement-treated specimens. In the vacuum saturation test, none of the three stabilizer types were significantly different from each other with respect to either UCS or retained UCS. Dielectric values measured during tube suction testing were lowest for cement-treated specimens, indicating that cement performed better than other stabilizers in reducing the moisture/frost susceptibility of the treated materials. The results also show that, as the stabilizer concentration level increased from low to high, specimens performed better in nearly all cases. A strong correlation was identified between UCS after the freeze-thaw test and UCS after the vacuum saturation test, while very weak correlations were observed between the final dielectric value after tube suction testing and all other response variables. Differences in variability between test results were determined to be statistically insignificant. Engineers interested in specifying a comparatively severe laboratory durability test should consider vacuum saturation testing for specimens treated with stabilizers similar to those evaluated in this research. The vacuum saturation test is superior to both the freeze-thaw and tube suction tests because of the shorter duration and lack of a need for daily specimen monitoring. Although the Class C fly ash used in this research performed well, further investigation of various sources of Class C fly ash is recommended because of the variability inherent in that material. Similar research should be performed on subgrade soils, which are also routinely stabilized in pavement construction. Research related to long-term field performance of stabilized materials should be conducted to develop appropriate thresholds for laboratory UCS values in conjunction with vacuum saturation testing.

Assunto cada vez mais em pauta nos foros nacionais e internacionais e nas comunidades ao redor do mundo, a questão ambiental tem sido a grande responsável pela geração de produtos novos. A construção de obras de infraestrutura é um dos maiores consumidores de recursos naturais, gerando uma enorme quantidade de resíduos, acaba também por ser um setor causador do impacto ambiental. Tais resíduos, se descartados de maneira incorreta geram problemas ambientais, em contraponto o descarte em aterros sanitários tem um custo bastante elevado. Partindo dessas premissas, buscar a utilização de resíduos como matéria prima para a indústria da construção de obras de infraestrutura é o objetivo global desta pesquisa, visando benefícios ambientais e econômicos. Para tal, foram utilizados a cinza volante, obtida através da queima do carvão nas termelétricas e rica em sílica e alumina e a cal de carbureto, oriunda da produção do gás acetileno e que possui grande quantidade de óxido de cálcio. Através de ensaios de laboratório, busca-se nesta pesquisa avaliar a influência da quantidade de cal e da porosidade, isoladamente, na durabilidade, resistência à tração e resistência à compressão e a relação resistência à tração/resistência à compressão, objetiva-se ainda avaliar a utilização do parâmetro porosidade/teor volumétrico de cal na estimativa de resistência e verificar a existência de uma relação única para este parâmetro versus a perda de massa acumulada/número de ciclos. Para isto, foram escolhidos os pesos específicos aparentes secos de 10,6, 11,6 e 12,6 kN/m³ com os respectivos teores de umidade de 36,6%, 31,3% e 25 %, sendo os teores de cal de carbureto adotados de 5, 8 e 11%. Todas as amostras foram curadas por um período de 28 dias em câmara úmida a 23°C. Os resultados apontam que o incremento da quantidade de cal e do peso específico aparente seco provocam aumentos na resistência à tração por compressão diametral, na resistência à compressão simples e na durabilidade da mistura. A utilização de um expoente como ajuste para a relação porosidade/teor volumétrico de cal [η/( ) , ] apresentou-se adequada para a formulação de equações para a previsão da resistência do material cimentado e para a estimativa da perda de massa acumulada/número de ciclos. Além disso, a existência de relações únicas para o controle da resistência à tração na compressão diametral e da resistência à compressão simples em função da porosidade e teor volumétrico de cal mostraram-se úteis para as formulações de dosagem.
The environmental issue is increasingly been responsible for the generation of new products. Infrastructure construction is one of the largest consumers of natural resources. Looking for the use of industrial residues as material for the construction industry is the overall objective of this research, aiming at environmental and economic benefits. For this, present study has used fly ash (obtained by burning coal in thermoelectric power plants) and carbide lime (originated from the production of acetylene gas) to fabricate a novel material. Through laboratory tests, one aim in this research was to evaluate the influence of the amount of lime and porosity of the blend on durability, splitting tensile strength and unconfined compressive strength, as well as on tensile/compressive ratio. Another objective was to further evaluate the use of the porosity/lime index in the estimation of strength and checking for a unique relationship for this parameter versus accumulated loss of mass/number of cycles. For such study were chosen dry unit weights of 10.6 kN/m³, 11.6 kN/m³ and 12.6 kN/m³ with the respective moisture contents of 36.6%, 31.3% and 25.0% and carbide lime contents of 5%, 8% and 11%. All samples were cured for a period 28 days in a moist chamber at 23°C. The results show that increasing dry unit weight and the amount of carbide lime cause increases in durability and splitting tensile and unconfined compressive strength of the studied blends. The use of an exponent as an adjustment to the porosity/lime index [η/( ) . ] showed to be appropriate for formulating equations for predicting the strength of cemented material and to estimate the accumulated loss of mass/number of cycles. Furthermore, the existence of unique relationships for the control of splitting tensile tests and unconfined compression strength as a function of porosity and volumetric lime content proved useful for the dosage formulations.

In the history of the concrete structures there was a time in which the mechanical resistance was the most important property for the designers. However due to amount of pathologies in the concrete structures and your respective worn-out amounts in recovery, other feature is being prioritized: the durability. And for environmental reasons as global heating, pollution and the raw materials decrease, the sustentability is prioritized. Aiming at collaborate to these factors these paper has as objective analyzes the microstructure of the covercrete with substitution in mass of 90% of cement for mineral additions. Were researched three types of concretes reference concrete (100%CPV-ARI), concrete with 70%Slag+20%FlyAsh and other similar mixture with addition of 20% of hydrated lime with the intention of partially restoring the hydroxide of calcium consumed by the pozzolanics reactions - named respectively of R, EV and EVC. Aims at, more specifically, to establish the differences microstructures of the covercrete of the prototypes(beams-70x20x15cm), through the tests of combined water, x-ray diffraction and scanning electron microscopy. For comparison effect, compressive strength test were also accomplished in molded cylinders(10x20cm) and cured in humid camera and in the cylinders(10x20cm) extracted of the cured prototypes in environmental conditions after 7 days of humid cure. Were studied three relationships a/ag: 0.40, 0.60 and 0.80 for the concrete R and 0.30, 0.40 and 0.50 for the concretes with additions, obtaining resistance between 20 and 70MPa. The tests of the microstructure were accomplished in the 91 and 300 days, with samples starting from the surface of the prototypes, in layers, in the depths of: 0-1.0cm(C1), 2.0-3.0cm(C2) and 4.5-5.5cm(C3). Evolution of the strength was accompanied in the ages of 28, 91, 182 and 300 days. Results were analyzed in equality of a/ag and compressive strength. For a/ag 0.40 and 0.50, to 28 days of age, in relation to reference concrete, the strength of the concrete EV was 54.0% on average of this, and the concrete EVC it was 68.5%. In the final age of 300 days, the percentile are of 72.5% and 76%. In both tests ages, with the increase of the depth of the layer occurs: decrease in the intruded volume total mercury, decrease in the tenor of combined water for the reference concrete and increment in the concretes with additions, decrease in the intensity of pick of the hydroxide of calcium in the three mixtures, decrease in the intensity of pick of the hydrated silicate for the reference concrete and increment in the concretes with mineral additions. Analysis on scanning electron microscopy showed refinement in the size of the grains, larger compact and uniformity in the mixtures with additions
Na história das estruturas de concreto houve período no qual a resistência mecânica foi a propriedade mais importante para os projetistas. Porém, devido ao surgimento de manifestações patológicas nas estruturas de concreto e seus respectivos montantes gastos em recuperação, outro aspecto também está sendo considerado: a durabilidade. Por motivos ambientais como aquecimento global, poluição e diminuição das matérias-primas, prioriza-se também a sustentabilidade. Visando colaborar com estes fatores o presente trabalho tem como objetivo analisar a microestrutura da camada de cobrimento de concretos com substituição em massa de 90% de cimento Portland por adições minerais. Foram pesquisadas três misturas: concreto de referência (100%CPV-ARI), concreto com 70%Escória+20%CinzaVolante e outra mistura similar com adição de 20% de cal hidratada com o intuito de repor parcialmente o hidróxido de cálcio consumido pelas reações pozolânicas as quais foram nomeadas respectivamente de R, EV e EVC. Objetiva, mais especificamente, estabelecer as diferenças microestruturais da camada de cobrimento de protótipos (vigas 70x20x15cm), através dos ensaios de porosimetria por intrusão de mercúrio, água combinada, difração de raios-X e microscopia eletrônica de varredura. Para efeito de comparação, também foram realizados ensaios de resistência à compressão em corpos-de-prova (10x20cm) moldados e curados em câmara úmida e em testemunhos (10x20cm) extraídos dos protótipos curados em condições ambientais após 7 dias de cura úmida. Foram estudadas três relações a/ag: 0.40, 0.60 e 0.80 para o concreto R e 0.30, 0.40 e 0.50 para os concretos com adições, obtendo resistências entre 20 e 70MPa. Os ensaios da microestrutura foram realizados aos 91 e 300 dias, com amostras a partir da face dos protótipos, em três camadas, nas profundidades: 0-1cm(C1), 2- 3cm(C2) e 4.5-5.5cm(C3). A evolução da resistência foi acompanhada nas idades de 28, 91, 182 e 300 dias. Os resultados foram analisados em igualdade de relação a/ag e resistência à compressão. Para as relações a/ag 0.40 e 0.50, aos 28 dias de idade, em relação ao concreto de referência, a resistência do concreto EV foi em média 54.0% deste, e o concreto EVC foi 68.5%. E na idade final de 300 dias, os percentuais são de 72.5% e 76%. Em ambas as idades de ensaio, com o aumento da profundidade da camada ocorreu: decréscimo no volume total intrudido de mercúrio, decréscimo no teor de água combinada para o concreto de referência e acréscimo nos concretos com adições, decréscimo na intensidade de pico do hidróxido de cálcio nas três misturas, decréscimo na intensidade de pico do silicato de cálcio hidratado para o concreto de referência e acréscimo nos concretos com adições minerais. A análise das micrografias mostrou refinamento no tamanho dos grãos, maior densificação e uniformidade nas misturas com adições

A grande questão de alinhavar progresso, crescimento, infraestrutura, demandas, consumo com sustentabilidade em um mundo com crescimento populacional exponencial ainda é um grande desafio para todos. Neste sentido, o desenvolvimento e utilização de novas técnicas e materiais que tenham a preocupação com a questão ambiental podem contribuir para um desenvolvimento mais sustentável nos processos construtivos. Sendo assim, o reaproveitamento de resíduos tornou-se uma alternativa eficaz para o desenvolvimento da sustentabilidade na indústria da construção. Dentre diversos resíduos gerados existem dois com grande potencial de aplicação na construção civil, sendo eles a cinza volante gerada em termelétricas e a cal de carbureto gerada na produção do gás acetileno que combinados geram ligantes. Entretanto, as reações pozolânicas responsáveis pela cimentação são notoriamente lentas o que em muitos casos inviabiliza o seu uso na construção civil. Portanto, a utilização de aceleradores que promovam um melhor comportamento mecânico em um menor período de cura deve ser avaliada. Outra importante questão se refere à possível presença de elementos-traços de metais pesados na cinza volante e na cal de carbureto que devem ser investigados quando utilizamos resíduos como matéria prima. Neste sentido, diversos ensaios de resistência à compressão simples, durabilidade por molhagem e secagem e lixiviação em coluna foram conduzidos. Resultados demonstraram que a utilização de NaCl promove melhoria no comportamento mecânico nas misturas de cinza-cal em menor período de cura devido ao incremento na formação de componentes hidratados, podendo ser considerado um acelerador. As variações do teor de cal, tempo de cura, NaCl, porosidade e temperatura de cura alteraram significativamente o comportamento da RCS e durabilidade. Foi possível a aplicação de relação entre porosidade e teor de cal (ajustada) na previsão da resistência e durabilidade da cinza estabilizada com cal. Com relação aos elementos traços, a cinza volante apresentou concentrações de arsênio (As), cromo (Cr) e selênio (Se) solubilizáveis em água acima dos limites para água potável, entretanto a estabilização da cinza com a cal e adição de NaCl diminuíram a concentração de metais pesados no extrato lixiviado no ensaio em coluna.
The big issue of tackling progress, growth, infrastructure, demands, and consumption with sustainability in a world with exponential population growth is still a great challenge for everyone. In this sense, the development and use of new techniques and materials that are concerned with the environmental issue can contribute to a more sustainable development in the construction processes. In this sense, waste reuse has become an effective alternative for the development of sustainability in the construction industry. Among several residues generated there are two with great potential of application in the civil construction, fly ash generated in thermoelectric and carbide lime generated in the production of the acetylene gas that combined generate binders. Therefore, the use of accelerators to facilitate a better mechanical behavior in a shorter curing period should be evaluated. Another important issue relates to the possible presence of heavy metals, trace elements, in fly ash and carbide lime, which should be investigated when using waste as raw material. In this sense, several tests of unconfined compressive strength, durability by wetting and drying and column leaching were conducted. Results showed that the use of NaCl promotes improvement in mechanical behavior in the fly ash-carbide lime mixtures in a shorter curing period due to the higher formation of hydrated components, which could be considered an accelerator for pozzolanic reactions. The variation of lime content, curing time, sodium chloride, porosity and curing temperature significantly altered the behavior of unconfined compression strength and durability. It was possible to apply a relationship between porosity and lime content (adjusted) in the prediction of the strength and durability of lime stabilized ash. Regarding trace elements, fly ash had concentrations of arsenic (As), chromium (Cr) and selenium (Se) that can be soluble in water above the limits for drinking water, however stabilization of fly ash with carbide lime and addition of NaCl decreased concentration of heavy metals in the column leaching test.

A questão ambiental vem se tornando tema recorrente nos foros nacionais e internacionais, estando atualmente inserida na opinião pública, nas comunidades e sendo norteadora na geração de novos produtos e serviços na área industrial e comercial voltados para a sustentabilidade. Neste sentido, a indústria da construção é um dos principais causadores de impacto ambiental, pois consome consideráveis recursos naturais e gera grandes quantidades de resíduos. Sendo assim, a utilização de resíduos como matéria prima na indústria da construção possibilita benefícios ambientais e econômicos. Buscando avançar nesta discussão, a presente pesquisa procurou inserir dois resíduos (cinza volante e cal de carbureto), gerados na região metropolitana de Porto Alegre, como possibilidade de solução de Engenharia. Para isto, é necessário um estudo do seu comportamento mecânico decorrente da cimentação proporcionada pela mistura e compactação destes materiais. Contudo, ainda não existe uma formulação de dosagem dessa mistura baseadas em critérios mais racionais. Assim, a presente pesquisa busca fornecer subsídios para que, através do uso da relação porosidade/teor volumétrico de cal obtidas a partir da identificação e quantificação das variáveis mais importantes no controle da resistência da mistura de dois resíduos, possa determinar o seu comportamento. Isto é, a formulação de equações para previsão da resistência à compressão simples do material cimentado em cura acelerada. Para isso, foram realizados ensaios de compressão simples em corpos-de-prova com 5, 10 e 15% de cal, com peso específico aparente seco de 11, 12 e 13 kN/m³; curados por 1, 3 e 7 dias em câmara vaporizadora nas temperaturas 40, 60 e 80°C; e 3, 7 e 14 dias para cura sem vapor a 23°C. Os resultados demonstram que o aumento da quantidade de cal, do peso específico aparente seco, do tempo de cura e da temperatura provoca o aumento da resistência à compressão simples da mistura compactada. Entretanto, a temperatura apresentou um limite de influência para 3 e 7 dias, onde a variação de 60°C para 80°C não aumentou a resistência. A relação porosidade(/teor volumétrico de cal (Lv), ajustado por um expoente [/(Lv)0,11], mostrou-se adequado na formulação de equações na previsão da resistência do material cimentado para todas as temperaturas e tempos de cura estudadas. Além disso, a existência de relações únicas e distintas no controle da resistência à compressão simples em função da porosidade, teor volumétrico de cal e temperatura, assim como para o tempo de cura mostraram-se úteis para formulações de dosagem. Os resultados foram submetidos à análise de variância que comprovou que todos os fatores controláveis escolhidos para o experimento são significativos, assim como todas as interações entre eles.
The environmental issue is becoming a recurring theme in national and international forums, currently inserted in the public opinion, communities and being guiding the generation of new products and services in the industrial and commercial area focused to sustainability. In this sense, the construction industry is a major cause of environmental impact, it consumes considerable natural resources and generates large amounts of waste. Thus, the use of waste as a raw material in the construction industry provides economic and environmental benefits. Looking for progress in this discussion, this research sought to insert two wastes (fly ash and carbide lime), generated in the metropolitan region of Porto Alegre, as a possibility for solution of Engineering. For this, a study of its mechanical behavior due to cementation and compaction provided by the mixture of these materials is necessary. However there is not a rational dosage formulation of this mixture. Therefore, this research seeks to provide subsidy to determine behavior through the use of the relation of porosity/volumetric lime content obtained from the identification and quantification of the most important variables in the controlling of strength to the mixture of two residues. That is, the formulation of equations for predicting the compressive strength of cemented material into accelerated healing. For this, tests were conducted on samples with 5, 10 and 15% of lime; with dry unit weight of 11, 12 and 13 kN/m³; for 1, 3 and 7 curing days with steam in the temperature of 40, 60 and 80°C; and 3, 7 and 14 days without steam for 23°C. The results show that increasing the amount of carbide lime, dry unit weight, curing time and temperature has as consequence the increase of unconfined compression strength of the compacted mixture. However, the temperature had a limit of influence for 3 and 7 days, where the range of 60°C to 80°C did not increase the unconfined compression strength. The porosity()/volumetric lime content (Lv) ratio adjusted by an exponent [/(Lv)0,11], proved to be adequate to formulate equations to predict the strength of the cemented material for all temperatures and curing times studied. Furthermore, the existence of unique and distinct relationships in the control of unconfined compression strength of the mixture studied as a function of porosity, lime volumetric content, temperature, as for the cure time proved to be useful in dosage formulations. The results were subjected to analysis of variance showing that all the controllable factors chosen for the experiment are significant, as well as all interactions between them.

The master´s thesis deals with the possibility of laboratory verification of the influence of feedstock character, especially lime and fly ash, on quality of fly ash aerated concrete. The experimental study involves taking a series of samples autoclaved and non-autoclaved aerated concrete during two pilot plant verification in the factory. After removal of autoclaved and non-autoclaved aerated concrete samples they were tested and compared with results of non-autoclaved aerated concrete produced in the laboratory. Methodology of comparison technologically-produced autoclaved aerated concrete and laboratory-produced non-autoclaved aerated concrete was designed based on achieved findings.

Diploma thesis gives an overview of artificial lightweight aggregates based on fly ash. Fly ash such as the residues of coal burning is currently one of the most used secondary raw materials for new building materials for research papers. The results shows that the secondary energy products are not just fully substitute the primary component, but in many cases improves the final properties of building products. Wide complex of fly ashes not only from domestic sources was tested and it`s main properties important for it`s further application was determined. Laboratory production of artificial aggregates based on fly ash made by sintering and also by cold bonding and following manufacture of artificial fly ash aggregates in technological conditions are also solved. The thesis is simultaneously concentrate on review of the suitability of fly ash aggregates in lightweight concrete.It was found that the highest quality fly ash for the production of sintered fly ash aggregate is fly ash and FBC ash is the best for the production of cold bonded aggregates. It was also verified that both types of aggregates are applicable to lightweight concrete class LC 20/22. The vast majority of manufactured aggregates is suitable for the production of lightweight concrete class LC 30/33. It was demonstrated that the sintered fly ash aggregates can be also used for high strength lightweight concrete class LC 50/55. Tests have also verified that all tested fly ashes and products produced from them meet the requirements of legislation on environment.

Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Acidic soils are a major limitation to agriculture worldwide. The Highveld in South Africa has many acidic soils and several coal burning power stations. These coal burning power stations generate alkaline fly ash as a waste material and it can thus serve as an ameliorant to the surrounding acidic soils. A two year field trial was undertaken to compare fly ash and other calcium ameliorants to alleviate the effects of subsoil acidity on maize root development. The field trail was established on Beestepan Farm in Middelburg, Mpumalanga. It consisted of 24 treatments, each done in triplicate, rendering a total of 72 plots. The materials used were unweathered fly ash (CCE 10%), calcitic lime (CCE 77%) and Calmasil (a calcium silicate slag, CCE 99%). Calmasil and lime were applied at rates of 0-, 1-, 2-, and 4t/ha, while fly ash was applied at 0-, 7-, 14- and 28t/ha. These treatments were applied to an acidic sandy loam soils in the presence or absence of 4t/ha gypsum. Beans were harvested after the first season following the application of amendments and maize was harvested in the second season. Yield, root length, leaf and soil analysis was undertaken to evaluate the effectiveness of the different liming materials. The effect of the treatments on fertility indicators such as pH, exchangeable acidity, Ca and Mg was investigated. Results indicated that all liming materials increased topsoil pH, soil nutrient and base status and crop yield in both seasons. Calmasil was the superior liming material in all respects. Fly ash increased pH minimally but reduced exchangeable acidity by 12% and 24% in the first and second seasons, respectively. Fly ash increased topsoil Ca levels from 74 to 102mg/kg and subsoil Ca from 61 to 114mg/kg. Topsoil Mg levels were increased from 7.3 to 16mg/kg and subsoil Mg was increased from 9.4 to 13mg/kg. The consequence of these increased nutrients was the subsequent increased foliar uptake of Ca and Mg. The substantial increase in bean yield from 958 to 1724kg/ha and maize yield from 5569 to 7553kg/ha following ash application compared well with results obtained from lime and Calmasil application. This may partly be due to the presence of additional plant nutrients such as P and K in the fly ash. Dissolution behaviour of fly ash indicates that upon exposure to acidity the release of micronutrients like B, Co, Cu, Fe, Mo, Mn and Zn occurs, and preliminary data shows that there is comparatively little concern regarding heavy metal accumulation in crops. The application of 4t/ha gypsum had no effect on pH and decreased subsoil acidity only minimally however, subsoil Ca status and acid saturation levels were considerably improved which would possibly account for the overall beneficial effect on maize yield, increasing by an average of 1071kg/ha. It was not possible to make any conclusions relating treatment application and maize root length. This field trial has confirmed that fly ash can be used as an efficient liming material and that it compares well with traditional liming materials.
AFRIKAANSE OPSOMMING: Suurgronde is ‘n groot beperking tot landbou wêreldwyd. Die Suid Afrikaanse Hoëveld het menigte suurgronde en verskeie steenkool-aangedrewe kragstasies. Hiedie kragstasies produseer alkaliese vliegas as ‘n afvalproduk. Hierdie vliegas kan dus dien as ‘n grondverbeteringsmiddel vir die aangrensende suurgronde. ‘n Tweejarige veldproef was onderneem om vliegas met ander kalsium-bevattende grondverbetereringsmiddels te vergelyk om die effek van ondergrondse suurheid op mielies op te hef. Hierdie veldproef was opgeset te Beestepan plaas in Middelburg, Mpumalanga. Dit het bestaan uit 24 behandelings wat drie keer herhaal was en lewer dus ‘n totaal van 72 persele. Die kalkmateriale wat gebruik was, is onverweerde vliegas (KKE 10%), kalsitiese kalk (KKE 77%) en Calmasil (‘n kalsium silikaat slak, KKE 99%). Calmasil en kalk was toegedien teen 0-, 1-, 2-, en 4t/ha, en vliegas teen 0-, 7-, 14- en 28t/ha. Hierdie behandelinge was toegedien tot ‘n suur leemsand met of sonder gips. Gips was toegedien teen 4t/ha. Een jaar nadat behandelinge toegedien was, is boontjies geoes en mieles was die daaropvolgende jaar geoes. Opbrengs, wortel lengte blaar- en grondontledings was uitgevoer om effektiwiteit te evalueer. Die effek van die behandelinge op indikatore van grondvrugbaarheid soos pH, uitruilbare suurheid, Ca en Mg was ondersoek. Resultate dui daarop dat alle kalkmateriale die grond se voedingstof- en basisstatus, bogrond pH asook gewasopbreng verhoog het. Calmasil was die beste kalkmateriaal in alle opsigte. Vliegas het die pH minimaal verhoog, terwyl dit die uitruilbare suurheid verminder het met 12% en 24% in die eerste en tweede jaar onderskeidelik. Vliegas het bogrond Ca vlakke vanaf 74 tot 102mg/kg vermeer, sowel as ondergrond Ca vanaf 61 tot 114mg/kg. Bogrond Mg was vermeer vanaf 7.3 tot 16mg/kg, asook ondergrond Mg vanaf 9.4 tot 13 mg/kg. Die gevolg van hierdie verhoogde voedingstowwe was die toename van Ca en Mg in die blare van die gewasse. Die beduidende toename in opbrengste van boontjies vanaf 958 tot 1724mg/kg en mielies vanaf 5569 tot 7553kg/ha na die toediening van vliegas vergelyk goed met die resultate van kalk en Calmasil. Dit is gedeeltelik toe te skryf aan die teenwoordigheid van addisionele plantvoedingstowwe soos P en K in vliegas. Oplossingstudies van vliegas dui op die teenwoordigheid van mikrovoedingstowwe soos B, Co, Cu, Fe, Mo, Mn en Zn. Aanvanklike data wys dat daar relatief min kommer oor swaarmetaal akkumulasie in gewasse is. Alhoewel 4t/ha gips geen effek op pH gehad het nie, en ondergondrondse suurheid minimaal verminder het, het ondergrondse Ca en gevolglik suurversadiging heelwat verbeter. Dit mag moontlik as verduideliking dien vir die oorhoofse voordelige effek van gips op mielie opbrengste, wat verhoog het met ‘n gemiddelde 1071kg/ha. Oorvleuende omstandighede het daartoe gelei dat geen konkrete afleidings gemaak kon word oor die wortel lengte van die mielies nie. Hierdie veldproef bevestig dat vliegas as ‘n effektiewe kalkmateriaal gebruik kan word en goed vergelyk met tradisionele kalkmateriale.

The work deals with the development of a new thermal insulation material that contains a secondary raw materials or waste. It is an insulating material with the requirement of resistance to high temperatures - 200 ° C and 500 ° C. Type of material is determined by the way of reducing density - direct and indirect. Direct is achieved by adding lightweight aggregates, indirect is achieved by gas evolution through chemical reaction and the subsequent incorporation of gas into the structure of the material. This thesis is part of the MPO TIP č. FR-TI 2/340 project.

Etude d'un sable fin (sable de dune) stabilise par un liant cendres volantes-chaux: essais de compression triaxiales sur eprouvettes compactees a l'optimum practor modifie, mesures de la vitesse de propagation du son. Definition d'une droite permettant, a partir d'un essai de compression simple a 7 jours, de connaitre la resistance du materiau a 1 an; abaque pour determiner la composition du melange a partir de la resistance a la compression simple du sable

Comparaison des caracteristiques mineralogiques et des proprietes mecaniques de melanges equiponderaux de fillers calcaires, dolomitiques ou quartzeux avec 5 liants : ciment portland, ciment alumineux, ciment au laitier, cendres volantes chaux eteinte et fumees de silice condensees chaux residuaire. Evocation d'un nouveau liant routier, par melange de cendres volantes, fumees de silice condensees et chaux (l'additivite des proprietes se realisant pour des proportions particulieres)

The use of byproducts and industrial waste as pozzolanic, is an alternative to achieve the sustainability, economy and durability in concrete structures. This survey has as its purpose to analyze the effect on mechanical, elastic and deformation properties on concrete with a high level of granulated slag from blast furnace and fly ash in place of Portland bulk cement. The use of high levels of mineral additions has the purpose of increasing the durability and reducing the consumption of cement, the use of hydrated lime aims to activating these adittions, restore part of the calcium hydroxide consumed by the pozzolanic reactions, increasing the initial and final strength to the mixtures. This way, three mixtures of concrete have been studied: one of them without mineral additions, only using Portland cement (CP V-ARI), taken as a control, with relations a/c 0.40, 0.60 and 0.83, and two mixtures with mineral additions in place of cement in equal mass, with 70% of slag and 20% of fly ash, being one of them with addition of 20% of hydrated lime on the mass of binders in addition to the cement, both to the relations a/mc 0.30/0.33, 0.40 and 0.49, which have been renamed as R, EV and EVC. Tests were held to resistance to axial compression in bodies of evidence (10x20cm) the ages of 07 28, 91 and 300 days, whose results range from 18.2 MPa and 81 MPa, tests of resistance to traction by diametral compression and module of elasticity at 28, 91 and 300 days, as well as tests of total shrinkage on prismatic bodies of evidence (10x10x30 cm) at 28, 91, 180 and 300 days. The results of mechanical, elastic and strain resistance have been also correlated with some intervening and independent variables, as well as some existing regulatory requirements. The results have been analyzed to each trace individually, in relation to the control traces, in relation to the evolution of the resistance, effectiveness of the use of the hydrated lime and in equal relationship a/mc 0.4. In the analysis of the equal relationship a/mc 0.400, in the case of reference concrete, in the initial age, the resistance to the axial compression of the concrete EV was, in media, 72% of the one presented by it, being the resistance to the EVC 55%, and in the final age, 65% and 50% respectively. In the case of the traction by diametral compression, to 28 days the concrete EV presented 76% of the resistance of the reference, and the concrete EVC 58%. This relation to 300 days was 80% and 61% respectively. To the elasticity module, to 28 days, the concrete EV presented 82% and the EVC 70% of the result obtained by the reference mixture, maintaining this proportion until the final age (300 days). In the analysis of the total retraction, the concrete EV presented an inferior retraction 10% inferior to the reference trace, while the concrete EVC to 300 days presents a good retraction 16% superior to it. The observation through the conjuncture of the results found shows a satisfactory relation among the different traces studied, making feasible the use of high levels of mineral additions in substitution to the large portion of cement in bulk.
A utilização de subprodutos e resíduos industriais como pozolanas, é uma alternativa para atingir a sustentabilidade, economia e durabilidade em estruturas de concreto. Esta pesquisa possui o objetivo de analisar os efeitos nas propriedades mecânicas, elásticas e de deformação em concretos com elevados teores de escória granulada de alto-forno e cinza volante em substituição ao cimento Portland em massa. O uso de altos teores de adições minerais tem por fim o aumento da durabilidade e redução do consumo de cimento, tendo o uso de cal hidratada a finalidade de ativar estas adições, repor parte do hidróxido de cálcio consumido pelas reações pozolânicas, aumentando as resistências iniciais e finais das misturas. Desta forma, estudaram-se três misturas de concreto: uma sem adições minerais, somente com cimento Portland (CP V-ARI), tomada como referência, com relações a/c 0.40, 0.60 e 0.83, e duas misturas com adições minerais em substituição ao cimento em igual massa, com 70% de escória e 20% de cinza volante, sendo uma delas com adição de 20% de cal hidratada em relação á massa de aglomerantes em adição ao cimento, ambas para relações a/mc 0.30/0.33, 0.40 e 0.49, as quais foram renomeadas como R, EV e EVC. Foram realizados ensaios de resistência a compressão axial em corpos de prova (10x20 cm) nas idades de 07, 28, 91 e 300 dias, cujos resultados variaram entre 18.2 MPa e 81 MPa, ensaios de resistência a tração por compressão diametral e módulo de elasticidade aos 28, 91 e 300 dias, assim como ensaios de retração total em corpos de prova prismáticos (10x10x30 cm) aos 28, 91, 180 e 300 dias. Também se correlacionou os resultados das resistências mecânicas, elásticas e de deformação com algumas variáveis intervenientes e independentes apresentadas, assim como com algumas prescrições normativas existentes. Os resultados foram analisados para cada traço individualmente, em relação aos traços referências, em relação à evolução da resistência, eficiência do uso da cal hidratada e em igualdade de relação a/mc 0.4. Na análise de igualdade de relação a/mc 0.400, em relação ao concreto referência, na idade inicial, a resistência a compressão axial do concreto EV foi, em média, 72% da apresentada por este, sendo a resistência do EVC 55%, e na idade final, 65% e 50%, respectivamente. Em relação à resistência a tração por compressão diametral, aos 28 dias o concreto EV apresentava 76% da resistência do referência, e o concreto EVC 58%. Esta relação, aos 300 dias foi de 80% e 61% respectivamente. Para o módulo de elasticidade, aos 28 dias, o concreto EV apresentou 82% e o EVC 70% do resultado obtido pela mistura referência, mantendo-se esta proporção até a idade final (300 dias). Na análise da retração total, o concreto EV apresentou uma retração 10% inferior ao traço referência, enquanto o concreto EVC aos 300 dias apresentou uma retração 16% superior ao mesmo. A observação através da conjuntura dos resultados obtidos demonstra uma satisfatória relação entre os diferentes traços estudados, viabilizando o uso de elevados teores de adições minerais em substituição a grande parcela de cimento em massa.

Thanks to European environmental rules and regulations establishment, waste recycling has become a more and more relevant problematic. For manufacturing plants, especially those producing hazardous wastes, expenses linked to waste production have drastically increased over the last decades. In the proposed work, various hazardous and non-hazardous wastes, among: soda-lime and borosilicate glass cullet, cathode ray tubes glass, exhausted lime from fume abatement systems residues, sludge and slags from ferrous and non-ferrous metallurgy, and pre-stabilized municipal solid waste incinerators ashes are used to elaborate several compositions of glass-ceramics. High-temperature treatment (minimum 800 °C) associated to a Direct Sintering process (30 min) was an efficient way to stabilize chemically the final products. The impact of each waste on the final product’s mechanical properties was studied, but also their synergies between each other, when mixed together. Statistic mixture designs enabled to develop interesting products for modern building applications, such as porous tiles and lightweight panels destined to insulation, with a purpose of fulfilling multifunctional properties.
Grazie alle regole e normative ambientali europee istituite, il riciclaggio dei rifiuti è diventato una problematica sempre più rilevante. Per gli impianti di produzione, in particolare quelli che producono rifiuti pericolosi, le spese connesse allo smaltimento sono drasticamente aumentate negli ultimi decenni. Nel lavoro proposto, vari rifiuti, pericolosi o no, vengono utilizzati per elaborare diverse composizioni di vetroceramiche. Si distinguono rottami di vetro della produzione di finestre, di contenitori farmaceutici e di tubi catodici. I rifiuti non vetrosi invece sono calce esausta da residui di sistemi di filtrazione di fumi, scorie metallurgiche da leghe ferrose e non e ceneri da inceneritori. E' presentata nel presente lavoro la ricerca di un metodo di trattamento ad alta temperatura (minima 800 ° C) efficace per stabilizzare chimicamente il prodotto finale, tramite i diversi processi di sinterizzazione diretta, sinter-cristallizzazione e vetrificazione. Sono stati studiati gli effetti di ogni rifiuto sulle proprietà meccaniche del prodotto finale, ma anche le nuove funzionalità ottenute attraverso le sinergie risultanti dalla loro miscela. Miscele calibrate hanno permesso di sviluppare prodotti interessanti per applicazioni edilizie moderne, come le piastrelle porose e pannelli leggeri destinati all’isolamento.

Fly ash is a waste product from thermal power plants where pulverised coal is used for the generation of electricity. Fly ash is being utilised in the blended cements, additive for concrete and manufacturing of concrete blocks and bricks. Fly ash-lime-gypsum bricks are being manufactured and marketed throughout the country. The literature review on fly ash-lime-gypsum (FALG) mixtures as intended to manufacture bricks or blocks for masonry applications indicates several gaps in understanding the various aspects of the technology. The present thesis is an attempt to understand the behaviour of compacted stabilised fly ash mixtures for the manufacture of fly ash bricks and characteristics of masonry using such bricks. A brief introduction to the technology of compacted stabilised fly ash bricks for structural masonry is provided. Review of the literature on fly ash-lime and fly ash-lime-gypsum mixtures, and fly ash bricks is provided in chapter 1. Chapter 2 gives details of the experimental programme, properties of raw materials used in the experimental investigations, methods of preparing different types of specimens and their testing procedures. Chapter 3 deals with the strength and absorption characteristics of compacted stabilised fly ash mixtures in greater detail. The main focus of the investigations is on arriving at the optimum stabilizer-fly ash mixtures considering density, stabilizer-fly ash ratio, curing conditions, etc. as the variables. Therefore the parameters/variables considered in the investigation include: (a) density of the compacted fly ash mixture, (b) stabilizer-fly ash ratio, (c) curing duration (normal curing and steam curing) and (d) dosage of additives like gypsum. Some of the major conclusions of the investigations are (a) compressive strength of compacted stabilised fly ash mixtures is sensitive to dry density of the specimens and the strength increases with increase in density irrespective of stabiliser content and type of curing, (b) Optimum limefly ash ratio yielding maximum strength is 0.75, (c) addition of gypsum accelerates rate of strength gain for compacted fly ash-lime mixtures (d) for 28 days wet burlap curing optimum gypsum content yielding maximum strength is 2% and maximum compressive strength is achieved for lime contents in the range of 10 – 17%, (e) steam curing (at 80 °C for 24 hours) gives highest compressive strength for compacted fly ash-lime mixtures. Characteristics of compacted fly ash-lime, fly ash-lime-gypsum and fly ash-cement bricks and their masonry are presented in chapter 4. Compressive strength, elastic modulus, water absorption, initial rate of absorption, dimensional stability and durability of the bricks were examined. Compressive strength, flexure bond strength and stress strain relationship for the fly ash brick masonry using cement-lime mortar were evaluated. The investigations clearly show the possibility of producing bricks of good quality using compacted fly ash-lime gypsum mixtures. Wet compressive strengths of 8- 10 MPa was obtained for compacted fly ash-lime-gypsum bricks at the age of 28 days. Wet strength to dry strength ratio for these bricks is in the range of 0.55 – 0.67. Initial tangent modulus for the fly ash-lime-gypsum bricks in saturated condition is in the range of 8000 – 12000 MPa. There is a large scope for selecting optimum mix ratios of fly ash, sand, lime and other additives to obtain a specific designed strength for the brick. The thesis ends with Chapter 5 highlighting major conclusions of the investigations.

Fly ash is a waste product from thermal power plants where pulverised coal is used for the generation of electricity. Fly ash is being utilised in the blended cements, additive for concrete and manufacturing of concrete blocks and bricks. Fly ash-lime-gypsum bricks are being manufactured and marketed throughout the country. The literature review on fly ash-lime-gypsum (FALG) mixtures as intended to manufacture bricks or blocks for masonry applications indicates several gaps in understanding the various aspects of the technology. The present thesis is an attempt to understand the behaviour of compacted stabilised fly ash mixtures for the manufacture of fly ash bricks and characteristics of masonry using such bricks. A brief introduction to the technology of compacted stabilised fly ash bricks for structural masonry is provided. Review of the literature on fly ash-lime and fly ash-lime-gypsum mixtures, and fly ash bricks is provided in chapter 1. Chapter 2 gives details of the experimental programme, properties of raw materials used in the experimental investigations, methods of preparing different types of specimens and their testing procedures. Chapter 3 deals with the strength and absorption characteristics of compacted stabilised fly ash mixtures in greater detail. The main focus of the investigations is on arriving at the optimum stabilizer-fly ash mixtures considering density, stabilizer-fly ash ratio, curing conditions, etc. as the variables. Therefore the parameters/variables considered in the investigation include: (a) density of the compacted fly ash mixture, (b) stabilizer-fly ash ratio, (c) curing duration (normal curing and steam curing) and (d) dosage of additives like gypsum. Some of the major conclusions of the investigations are (a) compressive strength of compacted stabilised fly ash mixtures is sensitive to dry density of the specimens and the strength increases with increase in density irrespective of stabiliser content and type of curing, (b) Optimum limefly ash ratio yielding maximum strength is 0.75, (c) addition of gypsum accelerates rate of strength gain for compacted fly ash-lime mixtures (d) for 28 days wet burlap curing optimum gypsum content yielding maximum strength is 2% and maximum compressive strength is achieved for lime contents in the range of 10 – 17%, (e) steam curing (at 80 °C for 24 hours) gives highest compressive strength for compacted fly ash-lime mixtures. Characteristics of compacted fly ash-lime, fly ash-lime-gypsum and fly ash-cement bricks and their masonry are presented in chapter 4. Compressive strength, elastic modulus, water absorption, initial rate of absorption, dimensional stability and durability of the bricks were examined. Compressive strength, flexure bond strength and stress strain relationship for the fly ash brick masonry using cement-lime mortar were evaluated. The investigations clearly show the possibility of producing bricks of good quality using compacted fly ash-lime gypsum mixtures. Wet compressive strengths of 8- 10 MPa was obtained for compacted fly ash-lime-gypsum bricks at the age of 28 days. Wet strength to dry strength ratio for these bricks is in the range of 0.55 – 0.67. Initial tangent modulus for the fly ash-lime-gypsum bricks in saturated condition is in the range of 8000 – 12000 MPa. There is a large scope for selecting optimum mix ratios of fly ash, sand, lime and other additives to obtain a specific designed strength for the brick. The thesis ends with Chapter 5 highlighting major conclusions of the investigations.

Varieties of masonry units such as burnt clay bricks, stones and concrete products are used for masonry construction. Even though these materials are durable, they are considered as unsustainable options because of the issues concerning energy, environment and conservation of natural resources. The walling materials are consumed in bulk quantities and hence large quantities of natural resources are depleted. There is a need for energy efficient and environment friendly alternative materials for masonry. Fly ash is an industrial by-product from the coal based thermal power plants which can be exploited for manufacturing of masonry units such as fly ash blocks/bricks, which are an alternative for conventional masonry units. Fly ash-Lime-Gypsum (FaL-G) bricks can be manufactured by compaction of a mixture of fly ash-lime-gypsum and water. The behaviour of FaL-G brick masonry is inadequately explored area and hence the thesis is focused on understanding the flexural behaviour of FaL-G brick masonry and bond development phenomenon at FaL-G brick-mortar interface. A brief introduction to the fly ash-based masonry units and literature review with respect to utilizing fly ash in manufacturing masonry units are presented. Characteristics of raw materials used and the procedure followed in casting of masonry units/compacts, mortar and their assemblages including testing methods have been discussed. Characteristics of FaL-G brick, mortars, FaL-G brick masonry are presented. Apart from determining the stress-strain relationships for these materials shear strength parameters of FaL-G compact, mortar and brick-mortar joint were determined. Mohr-Coulomb failure envelopes for FaL-G compact and mortar are presented. The mechanism of bond development in masonry is discussed. FaL-G brick masonry shows considerably higher bond strength when compared with the bond strength of conventional brick masonry. Results of micro-structure analysis (SEM, XRD and TGA) of the FaL-G brick-mortar interfaces confirm the formation of chemical bond in addition to mechanical interlocking of cement hydration products into brick pores. Flexural behaviour of FaL-G brick masonry wallettes in the two orthogonal directions was studied. The flexural strength, displacement profiles and load-displacement curves were determined, and moment-curvature relationships were established. Linear elastic analysis performed closely predicted the cracking flexural stress in FaL-G brick masonry. A brief introduction to the computational modelling of masonry using different approaches has been presented. Literature review with respect to simplified micro-modelling approach has been discussed. The flexural behaviour of FaL-G brick masonry panels under lateral loads was predicted using a non-linear 3D finite element analysis. The finite element model reasonably predicted the flexural behaviour of FaL-G brick masonry panels. The thesis ends with summary of research work with a note on scope for further research.

Varieties of masonry units such as burnt clay bricks, stones and concrete products are used for masonry construction. Even though these materials are durable, they are considered as unsustainable options because of the issues concerning energy, environment and conservation of natural resources. The walling materials are consumed in bulk quantities and hence large quantities of natural resources are depleted. There is a need for energy efficient and environment friendly alternative materials for masonry. Fly ash is an industrial by-product from the coal based thermal power plants which can be exploited for manufacturing of masonry units such as fly ash blocks/bricks, which are an alternative for conventional masonry units. Fly ash-Lime-Gypsum (FaL-G) bricks can be manufactured by compaction of a mixture of fly ash-lime-gypsum and water. The behaviour of FaL-G brick masonry is inadequately explored area and hence the thesis is focused on understanding the flexural behaviour of FaL-G brick masonry and bond development phenomenon at FaL-G brick-mortar interface. A brief introduction to the fly ash-based masonry units and literature review with respect to utilizing fly ash in manufacturing masonry units are presented. Characteristics of raw materials used and the procedure followed in casting of masonry units/compacts, mortar and their assemblages including testing methods have been discussed. Characteristics of FaL-G brick, mortars, FaL-G brick masonry are presented. Apart from determining the stress-strain relationships for these materials shear strength parameters of FaL-G compact, mortar and brick-mortar joint were determined. Mohr-Coulomb failure envelopes for FaL-G compact and mortar are presented. The mechanism of bond development in masonry is discussed. FaL-G brick masonry shows considerably higher bond strength when compared with the bond strength of conventional brick masonry. Results of micro-structure analysis (SEM, XRD and TGA) of the FaL-G brick-mortar interfaces confirm the formation of chemical bond in addition to mechanical interlocking of cement hydration products into brick pores. Flexural behaviour of FaL-G brick masonry wallettes in the two orthogonal directions was studied. The flexural strength, displacement profiles and load-displacement curves were determined, and moment-curvature relationships were established. Linear elastic analysis performed closely predicted the cracking flexural stress in FaL-G brick masonry. A brief introduction to the computational modelling of masonry using different approaches has been presented. Literature review with respect to simplified micro-modelling approach has been discussed. The flexural behaviour of FaL-G brick masonry panels under lateral loads was predicted using a non-linear 3D finite element analysis. The finite element model reasonably predicted the flexural behaviour of FaL-G brick masonry panels. The thesis ends with summary of research work with a note on scope for further research.

In India the present generation of fly ash is around 150 million tonnes and utilization percentage is 55-60%. A lot of efforts and innovations are required to achieve 100% utilization. Fly ash in itself has little strength. But it gains strength in presence of additives. This investigation is an attempt to develop fly ash composite materials with lime and cement with respect to enhanced compressive strengths, tensile strengths, and shear parameters so as to evaluate the potential in geotechnical usage. Calcium carrying material as cement and lime were used as additives. Varying proportions of fly ash, lime and cement were mixed to develop the composite materials. Optimum moisture content, maximum dry density, unconfined compressive strength, Brazilian tensile strength, and shear strength parameters were determined at varying curing period. Fly ash with 5% lime was found to exhibit maximum compressive and tensile strength.

For popularizing the usage of fly ash as one of the dominant construction material, it is advisable to enhance and improve some properties of it by stabilizing it by addition of some suitable stabilizer like lime. This project work aims at evaluation of the effectiveness of addition of lime as an agent in stabilizing the waste product like fly ash and its suitability to be used as a construction material for structural fills and embankment materials. Fly ash used for experimentation in this project was collected from the thermal power plant of CPP- NSPCL, Rourkela Steel Plant. For evaluating the suitability of any construction material for various geotechnical engineering works its consistency properties, compaction properties, strength parameters and settlement properties are the most important properties to be tested. In this project, an attempt was made to evaluate the above stated geo-engineering properties of fly ash along with the treated fly ash with different proportion of lime. The overall testing program was conducted in two phases. In the first phase, the physical and chemical characteristics of the fly ash samples were studied by conducting Hydrometer analysis, UCS test, Permeability test and CBR test. In the second phase of the test program, fly ash was mixed with 2%, 4%, 8% and 12% of lime. Lime was added as a percentage of dry weight of Fly ash. The particular UCS samples were cured for 7, 15, 30, and 60 days with varying temperature of 10°C, 25°C, 45°C and 90°C respectively to evaluate the effect of curing temperature on strength of lime stabilized flyash.

The objective of the thesis is to use industrial wastes rather than natural soil, aggregates, etc. in roads and highway construction after enhancing its strength, stability and durability. Conventionally, soil, stone aggregates, sand, bitumen, cement etc. are used in construction of roads and highway. Characteristic materials being limited in nature and thereby need of alternate materials is necessary. Gigantic quantities of soil are utilized as a part of the development of street and parkway yet adequate quantity of soil of required quality is not available effectively. To meet this demand extensive deforestation is being done which cause deforestation, soil disintegration and loss of rich soil which hampers in the farming efficiency. Additionally, cost of procurement of suitable quality of material is increasing. Worried about this, the researchers are searching for option materials for thruway development, and modern waste item is one such class. Stabilization method highlighted in this thesis is mainly to enhance the inherent strength of wastes like fly ash and crushed blast furnace slag (CBFS). This will automatically reduce the use of natural soil in addition to mitigate the disposal problems of industrial solid wastes in a great way. Fly ash and blast furnace slag was collected from Rourkela steel plant (RSP). Tests were conducted by blending fly ash and blast furnace slag in different proportions. The compaction characteristics, strength properties and the bearing value of different mixes are determined. From the compaction tests the optimum moisture content and the maximum dry density are determined for respective mixes. The strength parameters that are the unconfined compressive strength and CBR value for different mixes compacted to their respective MDD at OMC are evaluated. Further these mixes are blended with lime varying as 0%, 2%, 4%, and 8% and the UCS values are determined after a curing period of 0, 7 and 28 days. Similarly, the soaked CBR values of lime stabilized mixes at 0%, 2%, 4%, and 8% are determined after a curing period of 0 and 28 days. The effect of lime, curing period, fly ash and slag content with the unconfined compressive strength values and California bearing ratio values were studied. From the experimental study, it was observed that with addition of blast furnace slag to fly ash- slag mixes, the MDD increases and thereby decreases its OMC value linearly. It was also observed that the UCS value of the fly ash- slag mixes increases with the addition of slag up to slag content of 80% and there after the same decreases with further increases in slag content. The mix with 80% slag shows higher value as compared to 100% slag in the mix. Similar trend was observed for the CBR value for the fly ash- slag mixes, and it was seen that with increase with the slag content the CBR values also increases. However, for 100% slag the CBR shows a lesser value. Higher UCS and CBR values were reported at 8% lime content having a curing period of 28 days. The objective of the present study is to access the suitability of lime stabilized fly ash- blast furnace slag mixes as a highway construction material. So it is concluded that appropriate blending of fly ash with slag gives a better strength compared to individual materials. Further the desired strength required for different component of road can be achieved by stabilizing the mix with appropriate amount of lime.

碩士
淡江大學
土木工程學系
85
The purpose of this thesis is to study the engineering properties of Tamsui laterite mixed by fly ash and lime . Fly ash is an industrial solid waste material, and is used in soil stabilization extensively. Lime is also a soil stabilizer. There are thirteen combinations of laterite-fly ash-lime mixtures in this study. The fly ash content ranges from zero to twenty percent, and the lime content ranges from zero to ten percent on the dry weight basic. Tests conducted in this study includes unconfined compression test, direct shear test, and one-dimensional consolidation test. The engineering properties of the mixes such as strength and consolidation were tested with respect to different curing time and methods. The results indicate that the improvements on the engineering properties of the mixes are: 1）The strength of laterite- fly ash-lime mixtures generally increases with the increasing of curing time and the increasing of lime amount. （2）The cohesion and angle of internal friction increase on all the mixes. （3）The compressibility and swelling potential of laterite- fly ash-lime mixtures decrease after curing for twenty-eight days.

The objective of the project is to use industrial wastes in place of natural soil in the construction of road and highway after increasing its strength, stability and durability by the method of stabilization using lime and RBI grade 81.Traditionally soil, stone aggregates, sand, bitumen, cement etc. are used for road construction. Natural materials being exhaustible in nature, its quantity is declining gradually. Huge amount of soil is used in the construction of road and highway but sufficient amount of soil of required quality is not available easily. For that reason large amount of trees are being cut which cause deforestation, soil erosion and loss of fertile soil which hampers in the agricultural productivity. Also, cost of extracting good quality of natural material is increasing. Concerned about this, the scientists are looking for alternative materials for highway construction, and industrial waste product is one such category. If these materials can be suitably utilized in highway construction, the pollution and disposal problems may be partly reduced. Stabilization is the method used in this project to increase the inherent strength of wastes like fly ash and blast furnace slag (BFS) using lime and RBI grade 81. The present project work aims at evaluating the effectiveness of lime and RBI Grade 81 in stabilizing the waste products like fly ash and BFS mixes and its suitability in road construction. This will save the natural soil in addition to addressing the disposal problems of industrial solid wastes in a great way. Fly ash was collected from the captive power plant (CPP-II) and BFS from the dump pad of Rourkela steel plant (RSP). The collected samples were oven dried and mixed thoroughly to get homogeneity in the Geotechnical Engineering laboratory. The samples were then kept in different air tight container for the project work. Samples were then prepared mixing fly ash and BFS with different percentage at an interval of 10% and standard proctor test was carried out to get optimum moisture content (OMC) and maximum dry density (MDD). Stabilized samples were prepared mixing fly ash and BFS with different percentage at an interval of 10% and with stabilizing agent lime and RBI grade 81 with increasing percentage as 0%, 2%, 4%, 6%, and 8%. The samples were then subjected to unconfined compressive test after 7, 14, 28 and 60 days of curing. The above samples were prepared using constant volume mould by static compression method.

Pozzolanic reactions play a key role in improving the compressive strengths of compacted fly ash-lime specimens. Based on studies performed with cement amended fly ash (FA), activation of fly ash-lime pozzolanic reactions should accelerate the rate of strength development and mobilize larger compressive strengths facilitating improved engineering performance of fly ash amended materials. Further, use of phosphogypsum (PG) is a cause of environmental concern as the material is acidic (pH < 3.0) and contains considerable amounts of fluoride (0.86%). The main research objectives of the thesis are to activate lime-fly ash reactions by thermal and chemical activation process and examine the efficacy of fly ash pozzolanic reactions in controlling fluoride release by phosphogypsum. A comprehensive laboratory experimental program was performed to examine the influence of curing temperature (thermal activation) and calcined PG addition (chemical activation) on lime-fly ash reactions. The kinetics of fly ash-lime reactions are examined by monitoring the reacted lime content as function of curing period and temperature. The influence of variations in fly ash/lime content and dry density on the compressive strength developed by specimens is evaluated. The thermodynamic parameters for the fly ash-lime (FA-L) reactions have been delineated. Fly ash-lime-phosphogypsum (FA-L-G) mixes in slurry and compacted states were monitored for fluoride released as function of curing period The influence of curing temperature in activating fly ash-lime reactions is first examined. Specimens were cured at 25°C (termed RTC or room temperature cured) and at 80° (termed SC or steam cured) to understand thermal activation of fly ash-lime reactions. The rate of lime consumption by SC specimens classified as 2 stage process. The robust increase during stage 2 of steam curing suggested that the lime-solidification reactions did not reach equilibrium even after 4 days of curing at the elevated temperature. While only 3.1 to 3.3 % of added lime was consumed after 28 days of curing at room temperature, much larger amounts of lime ( 8.6-9.3%) were consumed after 4 days of steam-curing. Further, the lime-fly ash reactions were accelerated by 6 to 7 folds on curing the specimens at elevated temperature. The results indicated that activation of lime-fly ash reactions by curing at elevated temperature besides accelerating the rate of strength development also facilitated development of larger strength. Analysis of the free energy change values (ΔG°) indicated that the lime solidification reaction alters from dis-favored (less spontaneous) to favoured (spontaneous) state on curing at 80oC. The positive ΔH° (enthalpy change) values for the fly ash-lime reactions indicated that the reactions are endothermic in nature and are facilitated by increase in curing temperature. Gypsum activation was achieved by addition of 2.5 to 5% calcined phosphogypsum to fly ash lime mixes and curing the compacted specimens at room temperature (FA-L-G specimens). The rate of lime consumption by FA-L-G specimens appeared to be three stage process. The mass of lime consumed by FA-L-G specimens was about 1.5 to 3 folds higher than values of the RTC and SC specimens. Additional lime is consumed by FA-L-G specimens in ettringite formation. A similarity existed between rate of lime consumed and rate of strength developed by the FA-L-G specimens. It is proposed that besides lime solidification reactions, densification of the matrix by filling up of voids by fine gypsum particles and compaction of matrix by the growth of ettringite crystals also contribute to compressive strength of FA-L-G specimens; this additional mechanism of strength development accounts for their higher compressive strength in comparison to the SC and RTC specimens despite similar initial lime addition values. The trend of results suggests that activation of FA-L reactions by calcined PG addition is more effective than steam curing. Comparison of ΔG° values of RTC, SC and FA-L-G specimens revealed that the spontaneity of the lime solidification reactions is least for RTC specimens and improves with addition of phosphogypsum and further improves on curing at elevated temperature. Fly ash-lime pozzolanic reactions substantially reduced the fluoride released from the FA-L-G specimens. The marked reduction in fluoride released by PG amended with fly ash and lime is ascribed to entrapment of PG particles in the cemented matrix formed by fly ash-lime pozzolanic reactions together with consumption of fluoride in formation of insoluble fluoride bearing compounds. The thesis brings out that activation of fly ash-lime reactions leading to quicker and larger compressive strength development is achieved by curing the compacted fly ash-lime specimens at 80°C for 24 hr or by addition of 2.5 to 5% of calcined PG to fly ash-lime mix and curing the compacted specimens at room-temperature. As larger strengths are developed by PG addition than by curing at 80oC, it is recommended that FA-L-G technique be adopted for manufacture of building materials in the civil engineering industry. This technique is also sustainable as it does not require energy for heating which is needed in the steam-curing technique.

Pozzolanic reactions play a key role in improving the compressive strengths of compacted fly ash-lime specimens. Based on studies performed with cement amended fly ash (FA), activation of fly ash-lime pozzolanic reactions should accelerate the rate of strength development and mobilize larger compressive strengths facilitating improved engineering performance of fly ash amended materials. Further, use of phosphogypsum (PG) is a cause of environmental concern as the material is acidic (pH < 3.0) and contains considerable amounts of fluoride (0.86%). The main research objectives of the thesis are to activate lime-fly ash reactions by thermal and chemical activation process and examine the efficacy of fly ash pozzolanic reactions in controlling fluoride release by phosphogypsum. A comprehensive laboratory experimental program was performed to examine the influence of curing temperature (thermal activation) and calcined PG addition (chemical activation) on lime-fly ash reactions. The kinetics of fly ash-lime reactions are examined by monitoring the reacted lime content as function of curing period and temperature. The influence of variations in fly ash/lime content and dry density on the compressive strength developed by specimens is evaluated. The thermodynamic parameters for the fly ash-lime (FA-L) reactions have been delineated. Fly ash-lime-phosphogypsum (FA-L-G) mixes in slurry and compacted states were monitored for fluoride released as function of curing period The influence of curing temperature in activating fly ash-lime reactions is first examined. Specimens were cured at 25°C (termed RTC or room temperature cured) and at 80° (termed SC or steam cured) to understand thermal activation of fly ash-lime reactions. The rate of lime consumption by SC specimens classified as 2 stage process. The robust increase during stage 2 of steam curing suggested that the lime-solidification reactions did not reach equilibrium even after 4 days of curing at the elevated temperature. While only 3.1 to 3.3 % of added lime was consumed after 28 days of curing at room temperature, much larger amounts of lime ( 8.6-9.3%) were consumed after 4 days of steam-curing. Further, the lime-fly ash reactions were accelerated by 6 to 7 folds on curing the specimens at elevated temperature. The results indicated that activation of lime-fly ash reactions by curing at elevated temperature besides accelerating the rate of strength development also facilitated development of larger strength. Analysis of the free energy change values (ΔG°) indicated that the lime solidification reaction alters from dis-favored (less spontaneous) to favoured (spontaneous) state on curing at 80oC. The positive ΔH° (enthalpy change) values for the fly ash-lime reactions indicated that the reactions are endothermic in nature and are facilitated by increase in curing temperature. Gypsum activation was achieved by addition of 2.5 to 5% calcined phosphogypsum to fly ash lime mixes and curing the compacted specimens at room temperature (FA-L-G specimens). The rate of lime consumption by FA-L-G specimens appeared to be three stage process. The mass of lime consumed by FA-L-G specimens was about 1.5 to 3 folds higher than values of the RTC and SC specimens. Additional lime is consumed by FA-L-G specimens in ettringite formation. A similarity existed between rate of lime consumed and rate of strength developed by the FA-L-G specimens. It is proposed that besides lime solidification reactions, densification of the matrix by filling up of voids by fine gypsum particles and compaction of matrix by the growth of ettringite crystals also contribute to compressive strength of FA-L-G specimens; this additional mechanism of strength development accounts for their higher compressive strength in comparison to the SC and RTC specimens despite similar initial lime addition values. The trend of results suggests that activation of FA-L reactions by calcined PG addition is more effective than steam curing. Comparison of ΔG° values of RTC, SC and FA-L-G specimens revealed that the spontaneity of the lime solidification reactions is least for RTC specimens and improves with addition of phosphogypsum and further improves on curing at elevated temperature. Fly ash-lime pozzolanic reactions substantially reduced the fluoride released from the FA-L-G specimens. The marked reduction in fluoride released by PG amended with fly ash and lime is ascribed to entrapment of PG particles in the cemented matrix formed by fly ash-lime pozzolanic reactions together with consumption of fluoride in formation of insoluble fluoride bearing compounds. The thesis brings out that activation of fly ash-lime reactions leading to quicker and larger compressive strength development is achieved by curing the compacted fly ash-lime specimens at 80°C for 24 hr or by addition of 2.5 to 5% of calcined PG to fly ash-lime mix and curing the compacted specimens at room-temperature. As larger strengths are developed by PG addition than by curing at 80oC, it is recommended that FA-L-G technique be adopted for manufacture of building materials in the civil engineering industry. This technique is also sustainable as it does not require energy for heating which is needed in the steam-curing technique.

Stabilization of expansive soils with various calcium–based stabilizers (lime and cement) directly or in combinations with other solid waste materials such as fly ash and ground granulated blast furnace slag (GGBS) etc. is common approach by many foundation engineers to improve the properties, and conquer the distress caused by undesirable swell–shrink in the soil. Several researches have also been dedicated to understanding the complex ionic reactions and their products, and the mechanisms by which they affect the behaviour of expansive soils. Also, protocol for the lime stabilization of soil is established for the determination of optimum lime content (OLC) based essentially on the compressive strength test. The mechanism of lime treatment works mainly through cementation of flocculated matrix caused by the reduction in repulsion between soil particles with pozzolanic reaction compounds. However, no detailed studies have been carried out to establish the relation between change in fabric and its influence on the properties of expansive soil. It is also not clear whether the optimum lime content will be the same to improve different properties viz., strength and volume change. Hence, the research is directed to address these issues by performing elaborate experimental investigations on geotechnical properties and understanding the mechanism in improvement through fundamental physico–chemical and micro–analytical studies. There are several cases documented in literatures where recent heaving and premature failures of structures constructed on lime and cement–treated soils containing sulfates exhibits, leading to question the validity of calcium-based stabilization. The failures in sulfate bearing soils are attributed to the formation and growth of ettringite/thaumasite minerals in certain environmental regime. It is Stabilization of expansive soils with various calcium–based stabilizers (lime and cement) directly or in combinations with other solid waste materials such as fly ash and ground granulated blast furnace slag (GGBS) etc. is common approach by many foundation engineers to improve the properties, and conquer the distress caused by undesirable swell–shrink in the soil. Several researches have also been dedicated to understand the complex ionic reactions and their products, and the mechanisms by which they affect the behaviour of expansive soils. Also, protocol for the lime stabilization of soil is established for the determination of optimum lime content (OLC) based essentially on the compressive strength test. The mechanism of lime treatment works mainly through cementation of flocculated matrix caused by the reduction in repulsion between soil particles with pozzolanic reaction compounds. However, no detailed studies have been carried out to establish the relation between change in fabric and its influence on the properties of expansive soil. It is also not clear whether the optimum lime content will be the same to improve different properties viz., strength and volume change. Hence, the research is directed to address these issues by performing elaborate experimental investigations on geotechnical properties and understanding the mechanism in improvement through fundamental physico–chemical and micro–analytical studies. There are several cases documented in literatures where recent heaving and premature failures of structures constructed on lime and cement–treated soils containing sulfates exhibits, leading to question the validity of calcium-based stabilization. The failures in sulfate bearing soils are attributed to the formation and growth of ettringite/thaumasite minerals in certain environmental regime. It is reported that this swell is either by crystal growth or, expansion by hydration of the new minerals formed. Research findings contradict the swell mechanism caused by ettringite and it is still a matter of active current research. Further, the mechanism related to strength behaviour of lime treated sulfate containing soil is not well understood. Among several factors influencing ettringite formation, sources and form of sulfate and availability of water play a key role to induce the expansion in lime treated soil which is often termed as “Sulfate Induced Heave” and soil as “Manmade Expansive Soil”. Gypsum is the main source of sulfate in the soil and soil containing gypsum is termed as gypseous soil. Gypsum is an unpredictable material due to its property of changing the chemical structure under certain temperature–pressure and situations where water exists, and hence gypseous soils are not preferred as construction material. Therefore, prior to investigation of sulfate induced heave in lime treated soil, the role of gypsum in the geotechnical behaviour of soil needs to be investigated to make clear the inconsistencies and contradictions in the research findings of different investigations. Hence, the study has been taken up to investigate the impact of varying gypsum content on behaviour of lime treated expansive soil after curing for different period. The mechanism of changes in strength and volume change behaviour of lime treated soil in the presence of gypsum has been elucidated through detailed micro–mechanistic analytical study. Several remedial measures are adopted to control the sulfate induced heave in lime treated soil. Fly ash is often used to suppress this undesirable heave. Utilization of fly ash supplies additional pozzolans (silica and aluminium) with collection of adequate divalent and trivalent cations (Ca2+, Al3+, Fe3+, etc.). However, the effect of additional aluminium supplied by the fly ash on ionic reactions, particularly with ettringite formation in lime treated gypseous soil is not well understood. It is interesting to know that gypsum is frequently used as an accelerating agent to improve properties of fly ash with lime. Hence, an attempt has been made to understand the role of fly ash on the properties of expansive soil treated with varying lime content and the same combination by using diminutive amount of gypsum with a view to find a solution to overcome the adverse effect of sulfate, particularly in the form of gypsum. Mechanism of the strength and volume change behaviour of soil treated with varying lime content in the presence of diminutive gypsum content are investigated and explained. Though, fly ash has been recommended to control the sulfate induced heave in lime treated soil, no particular attention is given to quantify the amount of fly ash to suppress the heave. Also, the effect of intrusion of additional ions (silica and alumina), which are known to affect mineralogy and microstructure, altering the particle size by fly ash to soil is not understood. Hence, work is extended to compare and explore the effect of varying fly ash content on the behaviour of soil, lime treated soil and lime treated gypseous soil and deduce the mechanism through physico–chemical and micro–analyses studies.

碩士
淡江大學
土木工程學系
92
The purpose of this thesis is to study the engineering properties of a clay mixed by fly ash and lime. Fly ash is a solid waste material usually from burning coal by the power plant; lime is a relatively cheap material and used in soil improvement extensively. Both of them can be utilized in soil improvement, but also reduce the environmental problems. There are thirteen combinations of clay-fly ash-lime mixtures in this study. The fly ash content ranges from zero to twenty percent, and the lime content ranges from zero to ten percent, on the dry weight basis. In this study, the tests conducted include the unconfined compression tests, direct shear tests, and one-dimensional consolidation tests. The results indicate that the improvements on engineering properties are as followings. (1) With the addition of fly ash and lime, the maximum dry density of each combination decreases and the optimum water content increases. (2) The strength of clay-fly ash-lime mixtures generally increases with the curing time. The strength of the specimen that cured for seven days reaches at least 68% of the strength of specimen that cured for twenty-eight days. (3) Compared with the pure clay, the change of the clay mixed with fly ash and lime in the angle of internal friction is not significant, but the cohesion increases. (4) The unconfined compressive strength of clay increases with the decrease of its water content. (5) The compression index decreases with the addition of lime and fly ash mixes.

The utilization of fly ash in India varies between 50-60% and the rest are disposed in ash ponds. The fly ash which are utilized for reclamation of low lying areas or which are used in geotechnical engineering application has the tendency of leaching the heavy metal pollutants and thus polluting the groundwater, surface water and surrounding soil. Also the discharge of effluents from waste water treatment plants may lead to pollution of the ground water. If these ground water pollution can be controlled by increasing the Cation Exchange Capacity of the sub soil through application of any of the additives such as lime, fly ash, cement etc. which also leads to increase in strength of the soil then that additive would be favourable in case of geotechnical projects where ground water pollution is of great concern. The present work aims to find the effect of additives namely Lime and Fly ash on Cation Exchange Capacity (CEC),Compaction characteristics, and Unconfined Compressive Strength (UCS) of two soils. The two soils used in this study are Sandy Clay (SC) and Low Plasticity Clay (CL).First the soils were mixed individually with varying contents of lime and fly ash to find out their effects on Cation Exchange Capacity (CEC) and for conducting Light compaction test to find the compaction characteristics. Then the treated soil samples compacted at Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) were tested for Unconfined Compressive Strength (UCS) at different Curing periods. From the experimental results obtained, it is observed that for both soils, Cation Exchange Capacity (CEC) decreases more with increase in fly ash content than with Lime content. Also Optimum Moisture Content (OMC) increases and Maximum Dry density (MDD) decreases with increase in Lime and Fly ash content for both the soil samples. The Unconfined Compressive Strength (UCS) increases with lime and fly ash content up to a certain limit beyond which further increase in lime and fly ash content does not increase the Unconfined Compressive Strength (UCS) The Unconfined Compressive Strength (UCS) increases more with increase in Lime content than by increase in fly ash content. The Unconfined Compressive Strength (UCS) increases with curing time.

Thermal power station in most countries is saddled with the problem of fly ash disposal and unless suitable avenues are found for its proper use, this would pose a gigantic problem to the power sector. Disposal of huge quantities of fly ashes without proper care causes considerable impact on the environment particularly the one leading to soil and groundwater contamination. On the other hand, fly ashes have many desirable properties which can find applications in civil engineering, especially in geotechnical engineering. The pozzolanic reactivity is one of the important properties of fly ashes that enhance its application. Thought the fly ashes with self – pozzolanic property are well utilized, fly ashes with insufficient free lime, such as class F fly ashes are being grossly underutilized and they form a considerable portion of fly ashes that are disposed. Yet another factor restricting the use of fly ash is the concern about the leachability of lime under field conditions particularly under saturated or partially saturated conditions. Hence an attempt is made in this thesis, to reduce the lime leachability of class F fly ashes with different additives. Thus, selection of right amounts of additives to reduce the lime leacability is an important aspect studied in this thesis. Effect of such as strength, compressibility, and CBR value is also investigated. Another simple way to reduce the problem of disposal of fly ash is to utilize it for the construction of waste disposal sites particularly for lining solid waste disposal facilities in place of the natural clay materials which are very often procured by excavating and transporting from far off places. Also, the capacities of fly ashes to sorb heavy metal that are likely to be present in the leachates generated from the industrial wastes have been studied. Of the other factors limiting the generous use of fly ashes is the leachability of several trace elements present in them. Hence the leachability of trace metals from fly ashes under different practical situations, before and after incorporating the selected additives for improving the engineering properties of fly ashes, has been studied. The thesis is presented in 10 chapters. The relevant background for the studies and scope of the work is given Chapter 1. Sources of the fly ashes collected for the investigating along with their physical and chemical properties are presented in chapter 2. Two low line fly ashes are collected directly from the electronic precipitators of the thermal power plants located at Neyvelli town of the Tamil nadu and Maddanur town of Andhra Pradesh, India, named NFA and MFA respectively. MFA has greater finer particle content than NFA. The particles of MFA Have rougher surface compared to those of NFA. Both of fly ashes have predominantly quartz and mullite phase in them. The silica, total lime and carbon contents which have major influence on the pozzolanic reactivity of fly ashes vary considerably in the both the fly ashes. Lime leachability is taken as the amount of lime that is converted into soluble form (by dissociation into calcium and hydroxyl ions) under a standardized condition. It can be used to asses the long term sustainability of the strength achieved in fly ashes with lime. Lime leachability studies have been conducted on the fly ashes stabilized with different additives in specially designed moulds. Results presented in Chapter 3 showed that leachability of lime in fly ashes increases with the increase in lime content though it is not in proportion to the increase in lime content. This is because the solubility of lime is less and is independent of the total lime present. The marginal reduction in leachability is mainly due to cemented matrix of fly ash inhibiting the leaching of time. The higher the strength of the matrix the lower is the leachability. Further it is made clear that at any lime content presence of gypsum reduces the time leachability which has been attributed to the transformation of pozzolanic compounds into less soluble form than the compounds formed with lime alone. With the increase in curing period, the amount of lime that leaches from the lime-stabilized fly ashes as well as those treated with gypsum to a considerable extent. The nature of alteration does not seem to change with time as revealed by a good correlation between lime leachability ratios obtained after 7 days and 14 days of curing periods. Chapter 4 presents the results of unconfined compressive strength tests carried out on fly ashes with varying lime and gypsum contents, before soaking and also soaking in several heavy metal solutions, along with the durability to the cycle of wetting and drying. The results revealed that the strength of low lime fly ashes increases with lime content significantly up to the optimum lime content of about 2.5 – 5% and gradually thereafter. Addition of gypsum of 1 – 2.5% increases the strength of fly ashes further at any lime content. Increase in strength with gypsum, which is quite significant at lower lime contents initially, is observed for a considerable period (up to 180 days) at higher lime contents. The increase in strength is as high as 40-fold in some instances. This increase in strength which is also more durable has been attributed to the formation of calcium – sodium – aluminium - silicate hydrate along with calcium silicate hydrate. Further, it is observed that fly ash which responds better to lime stabilization shows accelerated gain in strength due to the addition of gypsum at early curing periods than the fly ash that responds solely to lime. Decrease in lime leachability ratio is a good indication of the increased strength along with the increased durability. California Bearing Radio (CBR) values are of great significance in the utilization of fly ashes in bulk quantities for the construction of road and railway embankments and pavements. Studies conducted to determine the CBR values of fly ashes with different lime and gypsum contents after curing for different time periods are described in chapter 5. The CBR values are observed to increase with lime alone significantly up to 2.5% and only marginally beyond. But the increase in CRB values is considerable with gypsum at any lime content. The increase in CBR value is particularly more with 2.5% gypsum for fly ashes with 2.5% lime. The CBR values of stabilized fly ashes are generally higher for 5 mm depth of penetration than those for 2.5 mm one due to the high stiffness of the matrix formed even at low strain levels. The loss in CBR values with soaking is relatively more at lower curing the periods due to the improper cementation of particles. Even after this significant loss in CBR values, fly ashes with 2.5% lime and 2.5% gypsum register the maximum values after curing under soaked condition. Unlike in the case of unconfined compressive strength, lime leachability values could not be well correlated with the CBR values of fly ashes with different lime and gypsum contents since many more factors influence the CBR values than those of unconfined compressive strength alone. Chapter 6.brings out the effects of addition of lime alone and lime along with gypsum on the compressibility behaviour of the fly ashes. Since the fly ashes when treated with additives develop strength and exhibit lower compression with the passage of time, consolidation testing with conventional duration of load increment may not be appropriate. Hence an attempt has been made to assess the minimum duration of load increment necessary to study the compressibility characteristics of such materials. Thus the compressibility behaviour of fly ashes with additives has been studied using conventional consolidation test with different durations of load increments varying from 30 minutes to 48 hours. The results indicated that 30 minutes of duration of load increment can be used to assess the compressibility behaviour of such materials. The effect of lime which reduces the compression is seen to be maximum from the results obtained with the load duration increment of 30 minutes but gradually reduce with higher duration of load increment. It has also been observed that the rate of decrease in the compressibility is maximum up to 2.5% lime and thereafter gradual. The compressibility of lime –treated fly ashes further reduces when gypsum is incorporated, the optimum gypsum percentage being 2.5. This reduction in the compressibility of fly ashes enhanced by incorporating lime and gypsum makes them versatile in the construction of embankments and for structural fills, particularly reducing the time required in between laying of each lift. It has been brought out that decrease in the lime leachability decreases the compressibility of fly ashes. Fly ash has potential application in the construction of base liners of waste containment facilities. While most of the fly ashes improve in the strength with curing, the ranges of hydraulic conductivities they attain may often not meet the basic requirement of a liner material. Attempts to reduce the hydraulic conductivity by adding lime as gypsum along with lime to both the fly ashes are presented in chapter 7. Hydraulic conductivities of the compacted specimens have been determined in the laboratory using the falling head methods. It has been observed that the addition of gypsum reduces the hydraulic conductivity of the lime treated fly ashes. The reduction in the hydraulic conductivity of the fly ashes containing gypsum is significantly more of sample with high amounts of lime contents (as high as 1000 times) than those with lower amounts of lime. However, there is relatively more increases in the strengths of the samples with the inclusion of gypsum to the fly ashes even at lower lime contents. This is due to the fact that excess lime added to fly ash is not effectively converted in to pozzolanic compounds. Even the presence of gypsum is observed not to activate these reactions with excess lime. On the other hand the higher amount of lime in the presence of gypsum is observed to produce more cementitious compounds which block the pores in the fly ash. Amount of lime leached in the found to be directly related to the hydraulic conductivity inspite of many –fold variations in the hydraulic conductivity achieved by curing fly ash with lime and gypsum. The consequent reduction on the hydraulic conductivity of fly ash would be beneficial in reducing the leachability of trace elements in the fly ash when used as base liner. Fly ash contains trace metals and other substances in the sufficient quantities which may leach out over a period of time. The study has been extended to examine the leachability of a few selected trace metals viz., Cd, Cu, Cr, Mn, Pb and Zn from fly ash before and after incorporating additives has been reported in chapter 9. The standard laboratory leaching test for the combustion residues developed by Van der Sloot et al. has been employed to study the leachabilities of trace elements as a function of liquid to solid (L/S) ratio and pH. The leachability test were conducted on the powdered fly ash samples obtained from unconfined compressive strength tests, conducted after a curing period of 28 and 180 days. It observed that, there is a marked reduction in the relative leachabilities of trace elements present, at the end of 28 days which reduced only marginally at the end of 180 days. Chapter 9 reports the retention capacities of fly ashes for copper, lead and zinc metals ions. Various parameters like contact time, initial concentration and pH have been varied and their effect on retention mechanism studied. The retention order of metals ions, Cu+ 2 > Pb+2>Zn+2, is observed to be the same for both the fly ashes at all pH values. The dominant mechanisms responsible for the retention are precipitation at higher pH’s as hydroxides and adsorption at lower pH’s Due to presence of silica and alumina oxide surface in fly ash. First order kinetic plots have revealed that the rate constant value increases with increase in initial concentration and pH. Langmuir adsorption isotherms have been plotted to study the maximum adsorption isotherms have been plotted to study the maximum adsorption capacities for metal ions under different conditions. The older indicates that the adsorption is predominantly by silica surface than that by alumina or iron oxide surfaces. This thesis demonstrates that incorporation of gypsum along with lime in the optimal proportions not only reduces the lime leachability but also greatly enhances the strength and CBR values, reduces the compressibility and minimizes the leaching of trace elements present in them enhancing the potential of fly ashes for many applications. Detailed conclusions are presented in chapter 10. The study greatly helps in promoting the use of fly ashes for many geotechnical and geo-environmental applications.

Thermal power station in most countries is saddled with the problem of fly ash disposal and unless suitable avenues are found for its proper use, this would pose a gigantic problem to the power sector. Disposal of huge quantities of fly ashes without proper care causes considerable impact on the environment particularly the one leading to soil and groundwater contamination. On the other hand, fly ashes have many desirable properties which can find applications in civil engineering, especially in geotechnical engineering. The pozzolanic reactivity is one of the important properties of fly ashes that enhance its application. Thought the fly ashes with self – pozzolanic property are well utilized, fly ashes with insufficient free lime, such as class F fly ashes are being grossly underutilized and they form a considerable portion of fly ashes that are disposed. Yet another factor restricting the use of fly ash is the concern about the leachability of lime under field conditions particularly under saturated or partially saturated conditions. Hence an attempt is made in this thesis, to reduce the lime leachability of class F fly ashes with different additives. Thus, selection of right amounts of additives to reduce the lime leacability is an important aspect studied in this thesis. Effect of such as strength, compressibility, and CBR value is also investigated. Another simple way to reduce the problem of disposal of fly ash is to utilize it for the construction of waste disposal sites particularly for lining solid waste disposal facilities in place of the natural clay materials which are very often procured by excavating and transporting from far off places. Also, the capacities of fly ashes to sorb heavy metal that are likely to be present in the leachates generated from the industrial wastes have been studied. Of the other factors limiting the generous use of fly ashes is the leachability of several trace elements present in them. Hence the leachability of trace metals from fly ashes under different practical situations, before and after incorporating the selected additives for improving the engineering properties of fly ashes, has been studied. The thesis is presented in 10 chapters. The relevant background for the studies and scope of the work is given Chapter 1. Sources of the fly ashes collected for the investigating along with their physical and chemical properties are presented in chapter 2. Two low line fly ashes are collected directly from the electronic precipitators of the thermal power plants located at Neyvelli town of the Tamil nadu and Maddanur town of Andhra Pradesh, India, named NFA and MFA respectively. MFA has greater finer particle content than NFA. The particles of MFA Have rougher surface compared to those of NFA. Both of fly ashes have predominantly quartz and mullite phase in them. The silica, total lime and carbon contents which have major influence on the pozzolanic reactivity of fly ashes vary considerably in the both the fly ashes. Lime leachability is taken as the amount of lime that is converted into soluble form (by dissociation into calcium and hydroxyl ions) under a standardized condition. It can be used to asses the long term sustainability of the strength achieved in fly ashes with lime. Lime leachability studies have been conducted on the fly ashes stabilized with different additives in specially designed moulds. Results presented in Chapter 3 showed that leachability of lime in fly ashes increases with the increase in lime content though it is not in proportion to the increase in lime content. This is because the solubility of lime is less and is independent of the total lime present. The marginal reduction in leachability is mainly due to cemented matrix of fly ash inhibiting the leaching of time. The higher the strength of the matrix the lower is the leachability. Further it is made clear that at any lime content presence of gypsum reduces the time leachability which has been attributed to the transformation of pozzolanic compounds into less soluble form than the compounds formed with lime alone. With the increase in curing period, the amount of lime that leaches from the lime-stabilized fly ashes as well as those treated with gypsum to a considerable extent. The nature of alteration does not seem to change with time as revealed by a good correlation between lime leachability ratios obtained after 7 days and 14 days of curing periods. Chapter 4 presents the results of unconfined compressive strength tests carried out on fly ashes with varying lime and gypsum contents, before soaking and also soaking in several heavy metal solutions, along with the durability to the cycle of wetting and drying. The results revealed that the strength of low lime fly ashes increases with lime content significantly up to the optimum lime content of about 2.5 – 5% and gradually thereafter. Addition of gypsum of 1 – 2.5% increases the strength of fly ashes further at any lime content. Increase in strength with gypsum, which is quite significant at lower lime contents initially, is observed for a considerable period (up to 180 days) at higher lime contents. The increase in strength is as high as 40-fold in some instances. This increase in strength which is also more durable has been attributed to the formation of calcium – sodium – aluminium - silicate hydrate along with calcium silicate hydrate. Further, it is observed that fly ash which responds better to lime stabilization shows accelerated gain in strength due to the addition of gypsum at early curing periods than the fly ash that responds solely to lime. Decrease in lime leachability ratio is a good indication of the increased strength along with the increased durability. California Bearing Radio (CBR) values are of great significance in the utilization of fly ashes in bulk quantities for the construction of road and railway embankments and pavements. Studies conducted to determine the CBR values of fly ashes with different lime and gypsum contents after curing for different time periods are described in chapter 5. The CBR values are observed to increase with lime alone significantly up to 2.5% and only marginally beyond. But the increase in CRB values is considerable with gypsum at any lime content. The increase in CBR value is particularly more with 2.5% gypsum for fly ashes with 2.5% lime. The CBR values of stabilized fly ashes are generally higher for 5 mm depth of penetration than those for 2.5 mm one due to the high stiffness of the matrix formed even at low strain levels. The loss in CBR values with soaking is relatively more at lower curing the periods due to the improper cementation of particles. Even after this significant loss in CBR values, fly ashes with 2.5% lime and 2.5% gypsum register the maximum values after curing under soaked condition. Unlike in the case of unconfined compressive strength, lime leachability values could not be well correlated with the CBR values of fly ashes with different lime and gypsum contents since many more factors influence the CBR values than those of unconfined compressive strength alone. Chapter 6.brings out the effects of addition of lime alone and lime along with gypsum on the compressibility behaviour of the fly ashes. Since the fly ashes when treated with additives develop strength and exhibit lower compression with the passage of time, consolidation testing with conventional duration of load increment may not be appropriate. Hence an attempt has been made to assess the minimum duration of load increment necessary to study the compressibility characteristics of such materials. Thus the compressibility behaviour of fly ashes with additives has been studied using conventional consolidation test with different durations of load increments varying from 30 minutes to 48 hours. The results indicated that 30 minutes of duration of load increment can be used to assess the compressibility behaviour of such materials. The effect of lime which reduces the compression is seen to be maximum from the results obtained with the load duration increment of 30 minutes but gradually reduce with higher duration of load increment. It has also been observed that the rate of decrease in the compressibility is maximum up to 2.5% lime and thereafter gradual. The compressibility of lime –treated fly ashes further reduces when gypsum is incorporated, the optimum gypsum percentage being 2.5. This reduction in the compressibility of fly ashes enhanced by incorporating lime and gypsum makes them versatile in the construction of embankments and for structural fills, particularly reducing the time required in between laying of each lift. It has been brought out that decrease in the lime leachability decreases the compressibility of fly ashes. Fly ash has potential application in the construction of base liners of waste containment facilities. While most of the fly ashes improve in the strength with curing, the ranges of hydraulic conductivities they attain may often not meet the basic requirement of a liner material. Attempts to reduce the hydraulic conductivity by adding lime as gypsum along with lime to both the fly ashes are presented in chapter 7. Hydraulic conductivities of the compacted specimens have been determined in the laboratory using the falling head methods. It has been observed that the addition of gypsum reduces the hydraulic conductivity of the lime treated fly ashes. The reduction in the hydraulic conductivity of the fly ashes containing gypsum is significantly more of sample with high amounts of lime contents (as high as 1000 times) than those with lower amounts of lime. However, there is relatively more increases in the strengths of the samples with the inclusion of gypsum to the fly ashes even at lower lime contents. This is due to the fact that excess lime added to fly ash is not effectively converted in to pozzolanic compounds. Even the presence of gypsum is observed not to activate these reactions with excess lime. On the other hand the higher amount of lime in the presence of gypsum is observed to produce more cementitious compounds which block the pores in the fly ash. Amount of lime leached in the found to be directly related to the hydraulic conductivity inspite of many –fold variations in the hydraulic conductivity achieved by curing fly ash with lime and gypsum. The consequent reduction on the hydraulic conductivity of fly ash would be beneficial in reducing the leachability of trace elements in the fly ash when used as base liner. Fly ash contains trace metals and other substances in the sufficient quantities which may leach out over a period of time. The study has been extended to examine the leachability of a few selected trace metals viz., Cd, Cu, Cr, Mn, Pb and Zn from fly ash before and after incorporating additives has been reported in chapter 9. The standard laboratory leaching test for the combustion residues developed by Van der Sloot et al. has been employed to study the leachabilities of trace elements as a function of liquid to solid (L/S) ratio and pH. The leachability test were conducted on the powdered fly ash samples obtained from unconfined compressive strength tests, conducted after a curing period of 28 and 180 days. It observed that, there is a marked reduction in the relative leachabilities of trace elements present, at the end of 28 days which reduced only marginally at the end of 180 days. Chapter 9 reports the retention capacities of fly ashes for copper, lead and zinc metals ions. Various parameters like contact time, initial concentration and pH have been varied and their effect on retention mechanism studied. The retention order of metals ions, Cu+ 2 > Pb+2>Zn+2, is observed to be the same for both the fly ashes at all pH values. The dominant mechanisms responsible for the retention are precipitation at higher pH’s as hydroxides and adsorption at lower pH’s Due to presence of silica and alumina oxide surface in fly ash. First order kinetic plots have revealed that the rate constant value increases with increase in initial concentration and pH. Langmuir adsorption isotherms have been plotted to study the maximum adsorption isotherms have been plotted to study the maximum adsorption capacities for metal ions under different conditions. The older indicates that the adsorption is predominantly by silica surface than that by alumina or iron oxide surfaces. This thesis demonstrates that incorporation of gypsum along with lime in the optimal proportions not only reduces the lime leachability but also greatly enhances the strength and CBR values, reduces the compressibility and minimizes the leaching of trace elements present in them enhancing the potential of fly ashes for many applications. Detailed conclusions are presented in chapter 10. The study greatly helps in promoting the use of fly ashes for many geotechnical and geo-environmental applications.

碩士
國立成功大學
土木工程學系碩博士班
97
The Alkali-activated cementitious materials refer to each kind of silicates and aluminosilicates which adds the solid or liquid state of alkali activator to initiate a reaction and produce the material with cementitious property. Due to the differences between the composition of material and the process of manufacture, both the harden mechanism and type of hydrate of Alkali-activated cementitious material differ from these of Portland cement In recent years, this Alkali-activated cementitious material is considered to have fabulous performance, for instance, high compressive strength, corrosion resistance, permeation resistance, durability, etc., are much better than these properties of Portland cement. In this study, the industrial waste such as Circulating Fluidized Bed(CFB) byproduct lime and mechanical activated fly ash were investigated as basic ingredient of alkali-activated cementitious materials. Attrition milling is carried out to improve reactivity of fly ash through size reduction and Calcium in byproduct lime can support the reactions. According to different mixture of materials, we discuss the experiment results, and make the analysis from material mechanical properties, to internal microstructure completely. The compressive strength increases continuingly in 28 days. It is also with well fluidity as an appropriate water:gel ratio. Scanning electron microscopy was used to observe the end products of alkali-activated cementitious materials, geopolymer gel and calcium silicate hydrate gel are included. However, because of its well apparel and firm structure, it is the reason mechanical excel in its performance.

Dissertação de mestrado integrado em Engenharia Civil
A sustentabilidade da construção é um assunto com grande influência e consequências na atualidade. Uma das medidas de modo a contribuir para a sustentabilidade é reduzir a produção e o consequente consumo de cimento que deriva da construção. A produção de cimento Portland origina a libertação de grandes quantidades de CO2 e consome grandes quantidades de energia. Como o betão é utilizado na construção em grandes quantidades, pode ser utilizado de maneira a nele serem incorporados resíduos e subprodutos industriais de forma segura e económica. Um exemplo é a incorporação de cinzas volantes de carvão provenientes de centrais termoelétricas. Betão com um elevado volume de cinzas volantes, possui uma reação pozolânica lenta e, portanto, a resistência mecânica inicial do betão é menor que o betão com cimento como único ligante. O destino de valorização mais comum dos resíduos florestais é a sua valorização térmica através da combustão. As cinzas volantes de biomassa têm características semelhantes às cinzas volantes de carvão, no entanto, são mais alcalinas (maior pH) e possuem um teor de cálcio maior. O principal objetivo deste trabalho consiste em avaliar a possibilidade de produzir betões de desempenho melhorado incorporando elevado volume de cinzas volantes de carvão, bem como utilizar pequenas quantidades de cinzas volantes de biomassa, de forma a mitigar alguns dos inconvenientes dos betões com elevado volume de cinzas volantes de carvão. Com base nos resultados obtidos, a durabilidade das composições com elevado volume de cinzas volantes, revelou-se, em geral, superior à da composição de referência, com exceção relativamente à resistência à carbonatação que, contudo, foi melhorada com a inclusão de uma reduzida quantidade de cinzas de biomassa. A cinza volante de carvão possuiu uma boa sinergia com quantidades reduzidas de cinza de biomassa que resultou numa boa atividade pozolânica.
The sustainability of construction is a subject with great influence and consequences at the present time. One of the measures to contribute to sustainability is to reduce the production and consequent consumption of cement that comes from construction. The production of Portland cement gives rise to the release of large amounts of CO2 and consumes large amounts of energy. As concrete is used in large-scale construction, it can be used to incorporate industrial waste and by-products in a safe and economical way. An example is the incorporation of coal fly ash from thermoelectric power plants. Concrete with a high volume of fly ash has a slow pozzolanic reaction and, therefore, the initial mechanical strength of the concrete is lower than the concrete with cement as the sole binder. The most common destination for forest residues is their thermal recovery through combustion. Biomass fly ash has characteristics similar to coal fly ash, however, they are more alkaline (higher pH) and have a higher calcium content. The main objective of this work is to evaluate the possibility of producing improved performance concrete incorporating a high volume of coal fly ash, as well as to use small amounts of biomass fly ash to mitigate some of the drawbacks of concretes with high volume of coal fly ash. Based on the obtained results, the durability of the compositions with a high volume of fly ash has generally proved to be superior to that of the reference composition, except for the resistance to carbonation which has however been improved by the inclusion of a reduced amount of biomass ash. Coal fly ash had a good synergy with reduced amounts of biomass ash which resulted in good pozzolanic activity.

Earth based construction materials are acknowledged as low carbon and low embodied energy materials. The investigations dealt in the thesis were mainly focused on exploring the geopolymer and lime-ground slag binders for the stabilised compressed earth bricks. A brief summary of the literature review on geopolymer and lime-pozzolana binders is presented. The thesis work is mainly based on experimental investigations. The initial part of the thesis presents the results of the investigations on the geopolymer stabilised compressed earth specimens and the brick specimens. Locally available red soil and pure clay minerals (kaolinite and montmorillonite) were used to cast the geopolymer stabilised compressed earth specimens. The investigations examine the role of clay and the alkali content on the strength of the geopolymer stabilised earth and pure clay specimens. Also, the influence of pozzolanas (ground slag and fly ash) on the strength of the specimens was examined. The results revealed the optimum mix proportions. The strength of the ground slag/fly ash based geopolymer specimens was nearly double that of non-ground slag/fly ash based geopolymer stabilised specimens. The characteristics of the geopolymer stabilised bricks such as strength, absorption, durability, and the stress-strain characteristics were examined in greater detail. The results showed the possibility of high strength (>20 MPa in wet state) bricks using a geopolymer binder. Investigations on using lime-pozzolana binder in the manufacturing process of the lime stabilised compressed earth bricks forms the next part of the thesis. The influence of clay, lime, and the pozzolana (ground granulated blast-furnace slag, i.e., GGBS) content on the strength of the specimens was examined in greater detail. The strength of the lime-pozzolana stabilised specimens increased with the increase in the pozzolana (ground slag) content. The long-term strength of the lime-pozzolana stabilised specimens was monitored. The results showed nearly 20% higher strength at the end of 365 days when compared to the strength of 28-day cured specimens. The investigations on the lime-GGBS stabilised compressed earth bricks showed that there is potential to obtain good quality bricks using lime-GGBS blended binders. The bricks showed satisfactory durability characteristics meeting the acceptable limits provided by the standards. The last part of the thesis deals with the investigations on the masonry using geopolymer and lime-GGBS stabilised compressed earth bricks. The strength (compressive strength and the flexure bond strength) and stress-strain characteristics of the masonry were examined through tests on masonry prisms. The results showed that the masonry bond strength increased with the increase in the surface porosity of the bricks. The results showed a linear relationship between brick strength and the masonry modulus. The thesis ends with a summary of the research outcome, contributions made to the knowledge domain, and the future work.

The aim of the present investigation is to improve the geotechnical properties of dispersive soil by reducing their dispersivity after elucidating the important mechanisms controlling the dispersivity of the soils. Dispersive soils have unique properties, which under certain conditions deflocculate and are rapidly eroded and carried away by water flow. These soils are found extensively in the United States, Australia, Greece, India, Latin America, South Africa and Thailand. The mechanism of dispersivity of soils is a subject matter of great interest for geotechnical engineers. In the earlier days clays were considered to be non erosive and highly resistant to water erosion. However, recently it was found that highly erosive clay soils do exist in nature. Apart from clayey soil, dispersivity is also observed in silty soils. The tendency of the clays to disperse or deflocculate depends upon the mineralogy and soil chemistry and also on the dissolved salts in the pore water and the eroding water. Such natural dispersive soils are problematic for geotechnical engineers. They are clayey soils which are highly susceptible to erosion in nature and contain a high percentage of exchangeable sodium ions, (Na+). It is considered that the soil dispersivity is mainly due to the presence of exchangeable sodium present in the structure. When dispersive clay soil is immersed in water, the clay fraction behaves like single-grained particles; that is, the clay particles have a minimum of electrochemical attraction and fail to closely adhere to, or bond with, other soil particles. This implies that the attractive forces are less than the repulsive forces thus leading to deflocculation (in saturated condition).This weakens the aggregates in the soil causing structural collapse. Such erosion may start in a drying crack, settlement crack, hydraulic fracture crack, or other channel of high permeability in a soil mass. Total failure of slopes in natural deposits is initiated by dispersion of clay particles along cracks, fissures and root holes, accelerated by seepage water. For dispersive clay soils to erode, a concentrated leakage channel such as a crack (even a very small crack) must exist through an earth embankment. Erosion of the walls of the channel then occurs along the entire length at the same time. Many slope and earth dam failures have occurred due to the presence of dispersive soils. Unlike erosion in cohesionless soils, erosion in dispersive clay is not a result of seepage through the pores of clay mass. However, the role of type of clay and its Cation exchange capacity in the dispersion of soil is not well understood. Data on the presence, properties, and tests for identification of dispersive clays is scarce. Hence, an attempt is made, in this thesis, to develop reliable methods to identify these soils and understand the extent of their dispersivity as well as to develop methods to control their dispersivity. The present study deals with the characterization of a local dispersive soil collected from southern part of Karnataka State. This study has focused on comprehensive tests to assess the dispersivity of the soils by different methods and to methods to improve geotechnical properties by reducing the dispersivity of the soil. An attempt is made to reduce the dispersivity of soil by using calcium based stabilizers such as lime, cement and fly ash. The mechanism of improvement in reducing the dispersivity of the soil with calcium based stabilizers has been studied. One of the important mechanism by which the dispersivity of the soil is reduced is by inducing cementation of soil particles. The differences in effectiveness of different additives are due to their differences in abilities to produce cementitious compounds. Although all the additives increased the strength of the soil and reduced the dispersivity of the soil, cement was found to significantly reduce the dispersivity of the soil, compared to the other two additives lime and fly ash. Cement is more effective as sufficient cementitious compounds are produced on hydration without depending on their formation. A detailed review of literature on all aspects connected with the present study is given in Chapter 2. A comprehensive description of dispersive soils present worldwide has been brought out in this section. Based on this survey, the scope of the present investigation has been elaborated at the end of the chapter. To understand the reasons for dispersivity of the soil and to estimate its degree of dispersivity, it is essential to assess standard methods to characterize the soil. Chapter 3 presents a summary of material properties and testing programs. The results of geotechnical characterization of the soil, the index properties of the soilspecific gravity, sieve analysis, Atterberg’s limits are discussed in Chapter 4. The physico chemical characteristics play an important role in determining the amount of dispersivity of the soil. Dispersive soils have two main characteristics which define its dispersivity chemically. These are Sodium Adsorption Ratio (S.A.R) and Exchangeable Sodium Percentage (E.S.P). The two characteristics are determined from the Cation exchange capacity of the soil. Exchangeable Sodium Percentage is defined as the concentration of sodium ions present in the soil with respect to the Cat ion exchange capacity of the soil. And Sodium Adsorption Ratio is used to quantify the free salts present in the pore water. Since Atterberg’s limits and grain size analysis do not help in identifying dispersive soils or in quantifying its dispersivity, two other tests- Emerson Crumb test and double hydrometer test were carried out on the soil. Emerson crumb test is a simple way for identification of dispersive soils. In this test, a crumb of soil measuring about 1mm diameter is immersed in a beaker containing distilled water and the subsequent reaction is observed for 5 minutes. It is solely based on direct qualitative observations. Depending on the degree of turbidity of the cloud formed in the beaker, the soil is classified in one of the four levels of dispersion in accordance with ASTM-D6572. Since this test is mainly a qualitative test and does not help in quantifying the dispersivity, it cannot be depended upon completely in identifying a dispersive soil. Another test double hydrometer test, which helps in quantifying the dispersivity of the soil, was also conducted on the soil. This test involves in conducting the particle size distribution using the standard hydrometer test in which the soil specimen was dispersed in distilled water with a chemical dispersant. A parallel hydrometer test was conducted on another soil specimen, but without a chemical dispersant. The dispersing agent used for the experiment was sodium hexametaphosphate. The percent dispersion is the ratio of the dry mass of particles smaller than 0.005 mm diameter of the test without dispersing agent to the test with dispersing agent expressed as a percentage. The double hydrometer test was carried out according to Double Hydrometer Test (ASTM D4221). Apart from the conventional tests, attempts are made to consider shrinkage limit test and unconfined compression test to determine the dispersivity of the soil. For this purpose, the shrinkage limit of the soil was determined with and without dispersing agent. The initial shrinkage limit of the untreated soil reduced on treating it with dispersing agent, thus indicating that the soil had further dispersed on addition of dispersing agent. In order to carry out the unconfined compression strength, the maximum dry density and optimum moisture content was determined through the compaction test. The soil was then treated with dispersing agent and compacted at the optimum moisture content. The soil exhibited high degree of dispersion through the strength test. Hence it is necessary to stabilize the soil with additives. Detailed experimental program has been drawn to find methods to improve the geotechnical properties and to reduce the dispersivity of the soil. Chapter 5 presents the investigations carried out on the dispersive soil with lime. The importance of lime stabilization and the mechanism of lime stabilization have been discussed initially. Commercially obtained hydrated lime was used in the present study. The soil was treated with three different percentages of lime 3, 5 and 8. The curing period was varied from one day to twenty eight days. The effect of addition of lime on various properties of the soil such as pH, Atterberg’s limits, compaction test and unconfined compression test is elaborated in chapter 5. The pH of the soil was maximum on addition of 3% lime. On further addition, the pH decreased and remained constant. The liquid limit of the soil increased on adding 3% lime and decreased with further lime content. The compaction test conducted on the soil showed an increase in maximum dry density of the soil and reduction in optimum moisture content with 3% lime content. On further increase in the lime content, the soil showed a decrease in the maximum dry density and increase in optimum moisture content. The unconfined compressive strength of the soil also increased on increasing lime content upto 5%. The variation in strength of the soil with respect to curing period was also compared. Optimum lime content arrived at based on the above conducted tests was 3%. The effect of lime in reducing the dispersivity of the soil through shrinkage limit test and unconfined compression test is also presented in this chapter. Details of the efforts made on the soil with fly ash are presented in Chapter 6.The fly ash used for stabilization of Suddha soil was of Class F type. This type of fly ash contains low reactive silica and lime. The effect of varying fly ash content on the properties of Suddha soil by varying the percentage of fly ash from 3 to 10 percentages is discussed in this chapter. The tests conducted on fly ash treated Suddha soil were pH test, compaction test, Atterberg’s limits and unconfined compression test with varying curing period. The fly ash treated Suddha soil was cured from one day to twenty eight days for the unconfined compressive strength analysis. The pH of the soil system increased with increasing percentage of fly ash. The increase in liquid limit was marginal on addition of fly ash. The maximum dry density of fly ash treated Suddha soil decreased continuously and the optimum moisture content of the treated soil increased with increasing fly ash content. The unconfined compressive strength of Suddha soil increased with increase in fly ash content upto 8% and then decreased for fly ash content of 10%. For all the percentages of fly ash added, the strength of the soil increased with increase in the curing period. The effect of fly ash in reducing the dispersivity of the soil was carried out using shrinkage limit and unconfined compression test. It was seen that on increasing the fly ash content, the soil treated with dispersing agent showed an increase in the shrinkage limit. Also, the same trend was observed for the unconfined compression strength to determine dispersivity. Optimum fly ash was determined as 8% with the help of all the tests conducted on the soil. Since the improvement in the properties of the soil with lime and fly ash was not very high, Cement was also considered as another additive used for stabilization of Suddha soil. It is known that soil with lesser amount of clay content will respond well with cement. The effect of cement addition on various properties of Suddha soil has been brought out in Chapter 7. It was found that addition of cement had positive effects on all the properties of Suddha soil. The pH of the soil increased for all the percentages of cement addition. The liquid limit of the soil increased on increasing the cement content. The shrinkage limit also showed a similar trend. The optimum moisture content of the soil decreased on increasing the cement content for Suddha soil and the maximum dry density increased for cement treated Suddha soil. The soil showed the maximum dry density at 8% cement content. The unconfined compression strength conducted on cement treated Suddha soil increased significantly for higher cement contents and also with curing period. Suddha soil when treated with 8% cement content exhibited maximum strength in comparison to other percentages. Also, the effect of cement in reducing the dispersivity of the soil was carried out using shrinkage limit and unconfined compression test. The shrinkage limit of the soil increased for all percentages of cement content, even in the presence of dispersing agent. Through the unconfined compression strength for dispersivity, it could be seen that 8% cement treated Suddha soil had the least dispersion. Optimum cement content was derived as 8% with the help of the tests conducted on the soil. A comparison of effect of all the additives on the strength of the soil as well as effect of the additives in reducing the dispersivity of the soil is discussed in Chapter 8. The effect of additives on the shrinkage limit of the soil with and without dispersing agent has been compared. The variation in shrinkage limit of the soil when treated with the additives was due to the different mechanisms involved in reducing the dispersivity by each additive. The effect on the unconfined compression strength of the soil treated with the additives with and without dispersing agent is also brought out in this chapter. It was noted that the dispersion exhibited through shrinkage limit test was lesser as compared to the percentage dispersivity exhibited through unconfined compression test. Hence it could be said that dispersion of the soil is due to loss of cohesion than volume change behavior. Also, the unconfined compression strength of the soils with respect to curing period is compared. The percentage dispersivity calculated through these tests is summarized and compared. With the help of this it could be said that to control the dispersivity of the soil, it is necessary to enhance the strength of the soil. The general summary and major conclusions drawn from the thesis are presented in Chapter 9.