Rozprawy doktorskie na temat „Pozzolanas”

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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
PROSUP - Programa de Suporte à Pós-Gradução de Instituições de Ensino Particulares
A destinação final ambientalmente adequada para os resíduos sólidos industriais é uma problemática que veio ganhando maior importância ao longo dos anos. O setor da construção civil consome grandes quantidades de insumos, gerando paralelamente grandes quantidades de resíduos. Quando o assunto é reciclagem de resíduos industriais, o setor da construção civil exerce um papel importante, reciclando resíduos de diversos setores da economia. Tendo em vista a existência do polo cerâmico no Rio Grande do Sul, e totalidade de resíduos de cerâmica vermelha (RCV) resultante desse polo, buscou-se através deste estudo, verificar qual é o percentual de geração de RCV em uma empresa específica, devido a grande variabilidade dos dados apresentados pela literatura. E em paralelo buscou-se avaliar o potencial pozolânico do RCV e comparar o seu desempenho com o metacaulim, material já consagrado como pozolana. Os aglomerantes (cimento CP II-F-32, Ca(OH)2 – P.A., CH-I) e os materiais pozolânicos (RCV e metacaulim) empregados na pesquisa foram caracterizados quimicamente por ensaios de fluorescência de raios X (FRX) e Perda ao Fogo (PF), mineralogicamente por ensaios de difração de raios X (DRX) e fisicamente por ensaios de, granulometria a laser, massa específica e área superficial específica (BET). Além disso, o RCV e o metacaulim foram submetidos a ensaios para determinação do teor de umidade e finura. Para avaliar a atividade pozolânica do RCV e comparar seu desempenho ao metacaulim foram realizados ensaios de condutividade elétrica, termogravimetria e ensaios de resistência à compressão, orientados pelas NBR 5752:2014, NBR 5751:2015 e NBR 15894:2010. Mediante os resultados obtidos, verificou-se que o percentual de geração de RCV na empresa objeto de estudo, com os ensaios de caracterização foi possível verificar que o RCV atende aos requisitos químicos estabelecidos pela NBR 12653:2014. O procedimento de moagem conferiu ao RCV uma granulometria adequada para uso como pozolona. Quanto a atividade pozolânica, verificou-se que o RCV atendeu ao requisito da NBR 12653:2014, no que diz respeito à resistência com o aglomerante Ca(OH)2 P.A., já quando ensaiado com o aglomerante CH-I, o RCV apresentou resistência à compressão consideravelmente superior ao metacaulim. Já nas argamassas moldadas com cimento, o RCV não atingiu o índice de atividade pozolânica (IAP) exigido na NBR 12653:2014, impedindo sua classificação como material pozolânico. Nas argamassas ensaiadas sob as prescrições da NBR 15894:2010, contendo 15% de substituição do cimento pelo RCV, os resultados de resistência à compressão não apresentaram diferenças significativas em relação às argamassas referência, apontando indícios de melhor desempenho em menores teores de substituição. As análises térmicas evidenciaram o consumo de Ca(OH)2 das pastas. As pastas formuladas com 25% de substituição do cimento por metacaulim apresentaram maior consumo de Ca(OH)2 em relação as pastas formuladas com 25% de RCV, evidenciando a atividade pozolânica dos materiais.
The final destination environmentally suitable for industrial solid waste is a problem that came gaining more importance over the years. The construction industry consumes large amounts of supplies, generating parallel large quantities of waste. When it comes to recycling of industrial waste, the construction sector plays an important role, recycling waste from various sectors of the economy. Considering the existence of the ceramic polo at the Rio Grande do Sul, and all red ceramic waste (RCV) resulting from this pole, we sought through this study, find what is the percentage of RCV generation in a specific company due the great variability of the data presented in the literature. And in parallel we sought to evaluate the potential of pozzolan RCV and compare their performance with metakaolin, material already recognized as pozzolan. The binder (cement CP II-F-32, Ca(OH)2 – P.A., CH-I) and pozzolanic materials (RCV and metakaolin) employed in the study were chemically characterized by X-ray fluorescence assays (XRF) and Loss Fire (PF), mineralogically by testing X-ray diffraction (XRD) and physically by tests of laser granulometry, specific gravity and specific surface area (BET). Furthermore, the RCV and metakaolin were subjected to tests for determination of humidity content and fineness. To evaluate the pozzolanic activity of the RCV and compare its performance to metakaolin were performed electrical conductivity tests, thermogravimetry and compressive strength tests, guided by the NBR 5752:2014, NBR 5751:2015 and NBR 15894:2010. From the results obtained, found to the percentage of RCV generation in study subject company with the characterization tests it was verified that the RCV meets chemical requirements of the NBR 12653:2014. The grinding procedure gave the RCV adequate particle size for use as pozolona. As the pozzolanic activity, it was found that the RCV met requirement the NBR 12653:2014 with regard to resistance to Ca(OH)2 P.A. agglomerating, since when tested with CH-I agglomerating, the RCV showed compression resistance the considerably higher than metakaolin. Already in the cast with cement mortar, the RCV has not reached the pozzolanic activity index (IAP) required in NBR 12653:2014 preventing classification as pozzolanic material. In mortars tested under the requirements of NBR 15894:2010, containing 15% replacement of cement by RCV, the compressive strength results showed no significant differences from the reference mortar, indicating better performance indications in lower replacement levels. The thermal analysis showed the consumption of Ca(OH)2 pastes. The pastes formulated with 25% of the cement replaced by metakaolin showed increased consumption of Ca(OH)2 relative pastes formulated with 25% RCV, showing the pozzolanic activity of the materials.

The extent of the benefits provided by use of SCMs in cementitious systems increases as their percentage amounts in total binder increases. However, the proportion of SCMs in cementitious systems is limited, especially for natural pozzolans, by some factors such as increase in water requirement and decrease in rate of strength development. Therefore investigations are needed to increase the amount of natural pozzolans in blended cements or in concrete as much as possible without decreasing their performance. This aim requires studies on cementitious systems with more reactive natural pozzolans than widely-used ones. The objective of the study was to investigate the pozzolanic activity of natural zeolites (clinoptilolite) from two localities in Turkey, and properties of cementitious systems containing low (15%), moderate (35%) and high (55%) amount of them. The study covers characterization of the natural zeolites used, evaluation of their pozzolanic activity in comparison with some popular mineral admixtures, and properties of pastes, mortars, and concrete mixtures containing low, moderate, and high amounts of natural zeolites. Reactivity of the natural zeolites with Ca(OH)2 was found to be higher than those of the fly ash and the non-zeolitic pozzolan, but lower than that of the silica fume. Natural zeolite blended cements were characterized with the following highlighted properties
faster setting than portland cement, low amounts of Ca(OH)2 and capillary pores larger than 50 nm in hardened pastes, relatively dense microstructure of hardened paste than portland cement, more compatibility with melamine-based superplasticizer than being with naphthalene-based one, and excellent compressive strength performance. Concrete mixtures containing natural zeolites as partial replacement for portland cement were characterized with the following properties
7-day compressive strength of ~25 MPa and 28-day strength of 45-50 MPa with only 180 kg/m3 portland cement and 220 kg/m3 zeolite dosages (55% replacement), comparable modulus of elasticity with plain portland cement concrete, &ldquo
low&rdquo
and &ldquo
very low&rdquo
chloride-ion penetrability for low and large levels of replacement, respectively.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Universidade Politecnica de Valencia- Espanha
O presente trabalho apresenta um método de produção de cinza de casca de arroz (CCA) altamente reativa e de coloração clara, bem como o seu comportamento em matrizes de cimento Portland com o intuito de avaliar a atividade pozolânica da CCA. O trabalho está dividido em quatro etapas, a saber: construção de um forno e produção da cinza de casca de arroz, caracterização físico-química da CCA, verificação da atividade pozolânica do material através de métodos instrumentais e, finalmente, ensaios mecânicos em argamassas de cimento Portland. O forno utilizado para a produção da cinza de casca de arroz não apresenta controle de temperatura e, o tempo de queima é bastante longo, aproximadamente 36 horas. Neste método obtém-se cerca de 1,5Kg de cinza por processo de queima. A cinza obtida apresenta uma coloração clara e o seu caráter amorfo foi determinado através de diferentes métodos: difração de Raio-X, determinação do teor de sílica amorfa, análise termogravimétrica, Microscopia Eletrônica de Varredura (MEV) e ensaios mecânicos em argamassas de cimento Portland. O programa experimental também abrange estudos de variação da finura da CCA e estudos com diferentes porcentagens, em substituição ao cimento Portland. Os resultados obtidos foram comparados...
This research show a method of production white amorphous Rice Husk Ash (RHA), therefore, the behaviour of RHA in Portland cement matrix to evaluate the pozzolanic activity of this material. The research can be shared in four steps, to know: construction of an oven and production of rice husk ash, physical-chemical analysis of the rice husk ash, evaluation of pozzolanic activity of the pozzolan though instrumental analysis and, finally, mechanical properties of Portland cement mortars. The oven used for production of rice husk ash didn't have a control of temperature and, the time of burning is so longer, approximately 36 hours. In this method is obtained for about 1,5Kg of ash. The obtained ash has white colour and its amorphous phase were determined though different methods: X-ray diffractometry, determination of amorphous silica, Termogravimetric Analysis (TA), scanning electron microscopy (SEM) and mechanical properties of Portland cement mortars. Besides that, the experimental procedure involves studies on fineness variation of rice husk ash and different degrees of Portland cement substitution. The obtained results were compared with silica fume, because this is the most similar pozzolanic material with rice husk ash. The RHA produced under this method can be used... (Complete abstract click electronic access below)

In this thesis, characterization of two class F fly ashes (FA) from Ç
atalagzi and Sugö
zü
thermal power plants were carried out and their utilization potentials in three different fields were examined. Characterization of sintered samples and determination of their utilization potentials in ceramic industry is the first research area in this thesis. For this purpose, the class F fly ash samples were first pressed into cylindrical specimen without the addition of any organic binders or inorganic additives, and then sintered to form ceramic materials. Effects of sintering temperature and time on sintering characteristics were investigated. In the experiments, the cylindrical specimens were first preheated to 300oC for 1 h to remove moisture and any other gases. The specimens were then fired at the temperatures of 1000oC, 1050oC, 1100oC and 1150oC for the sintering times of 0.5, 1.0, 1.5 and 2.0 hours. Heating rate of 10oC/min was kept constant throughout the experiments. Quality of sintered samples was evaluated in terms of ceramic specifications such as density, water absorption, porosity, shrinkage and splitting tensile strength. In addition, mineralogical and microstructural changes during sintering were determined with X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. According to literature data, better microstructure, the highest density and strength with the lowest porosity, water absorption and shrinkage values are the indications of the optimum sintering conditions. Based on these specifications, Sugö
zü
fly ash gave better results compared to Ç
atalagzi fly ash, and the optimum conditions were achieved at the sintering temperature of 1150oC for the sintering time of 1.5 hours for both samples. Pozzolanic reactivity of the fly ashes and their utilization potentials in civil engineering applications were also examined in detail during this study. For this purpose, Ç
atalagzi (CFA) and Sugö
zü
(SFA) fly ashes were first subjected to a specific hydraulic classification process developed at CAER (University of Kentucky, Center for Applied Energy Research) to recover ultrafine fly ash particles. The overflow products with average particle sizes of 5.2 &mu
m for CFA and 4.4 &mu
m for SFA were separated from the respective as-received samples with average particle sizes of 39 &mu
m and 21 &mu
m. After the classification stage, the pozzolanic activities of these ultrafine fly ash fractions (UFA) and as-received samples were examined by preparing a number of mortar (mixture of Portland cement (PC), FA or UFA as partial cement replacement, sand and water) and paste (mixture of PC, FA or UFA as partial cement replacement and water) specimens. Control samples containing only PC were also prepared and tested through the experiments for the comparison of the results. In the mortar experiments, three different PC replacement ratios by FA and UFA (10%, 20% and 30%) were used to examine the effects of FA and UFA samples on the fresh and hardened mortar properties such as water requirement, compressive strength, drying shrinkage and water expansion. These mortar tests indicated that ultrafine fractions of Ç
atalagzi (CUFA) and Sugö
zü
(SUFA) fly ashes provided more than 10% reduction in water demand compared to the control sample for 30% PC replacement. The mortar cubes containing CUFA and SUFA samples exhibited also higher strength development rates after 14 days compared to the ones with as-received samples and PC only. At the end of the curing age of 112 days, both CUFA and SUFA provided more than 40% increase in compressive strength compared to the control sample for the PC replacement ratios higher than 20%. As a comparison, SUFA gave better results than CUFA in both water demand and compressive strength tests. The mortar bars prepared with the both FA and UFA samples exhibited very low shrinkage and expansion values. These values decreased generally with increasing PC replacement ratio especially after 14 days. In the paste experiments, thermogravimetric analyses (TGA) of the paste specimens prepared by using only with 20% PC replacement were carried out to determine pozzolanic reactivity of the samples. The difference between the remaining Ca(OH)2 (portlandite) contents in the paste specimens containing the fly ashes and the reference PC paste was used as a measure of pozzolanic reactivity. After 112 days, 68.56% and 62.68% Ca(OH)2 content of PC only pastes were obtained with the pastes containing CUFA and SUFA samples, respectively, corresponding to 11% and 13% more Ca(OH)2 consumptions in reference to the respective as-received samples. X-ray diffraction (XRD) analyses were also performed for comparison of main portlandite peak intensities in the paste specimens containing FA or UFA with those in the PC only paste during cement hydration. According to these XRD analyses, portlandite content in PC/UFA pastes decreased significantly after 14 days compared to the PC only paste. All of these tests and analyses showed that a highly reactive lower cost pozzolan with very fine particle size and higher surface area compared to regular fly ash pozzolans can be produced from both Ç
atalagzi and Sugö
zü
fly ashes using a relatively simple hydraulic classification technology. Cenosphere recovery potentials from Ç
atalagzi and Sugö
zü
fly ashes were also studied in this thesis. Determination of cenosphere content was done under optical microscope by particle counting on the basis of point and area. Based on the point-counting data, CFA and SFA samples originally contain 11.30% and 4.50% cenospheres, respectively. Variations of cenosphere contents in the fly ash samples were examined by using float-sink, screening and air classification tests. The results pointed out that cenosphere contents decreased with decreasing size and increasing density for both samples. According to the float-sink tests, Ç
atalagzi fly ash has much more floating products and more cenospheres than Sugö
zü
fly ash for the same density interval. Based on the air classification results, cenospheres were concentrated in the underflow products, and cenosphere contents increased with increasing air pressure and decreasing motor speed for both samples. The most efficient cenosphere separation technique among the examined methods was screening. Cenosphere contents of CFA and SFA increased to 21.65% and 11.83%, respectively by only using simple screening through 38 &mu
m.

In recent years the disposal and the treatment of mine waste has been increasingly causing concern to the mining industry. One of the biggest challenges today is acid mine drainage (AMD), which is associated in particular with sulfide bearing tailings. As a consequence of AMD, heavy metals and sulfates are released into the environment.
This project has studied the effect of lime-based treatments in the stabilization of two sulfide tailings, one waste predominately containing pyrite minerals and the second containing pyrrhotite minerals. Different proportions of pozzolans (fly ash and slag) were also added to the lime-tailings mixtures. The physical properties of the mixtures have been evaluated, using several tests such as strength (unconfined compressive strength), permeability and durability. The mineralogical changes in the treated wastes were also examined. The stabilization process and the treatment validity would not be complete without a chemical analysis of the treated waste; therefore a quantitative analysis was performed, including leaching and extraction tests for some elements (Zn, Mg, Ca, and Fe), and also sulfate measurement. The samples were tested after 1 and 28 days of curing time. (Abstract shortened by UMI.)

The thesis describes a study undertaken to determine the effect of air entrainment on workability and air content of fresh concrete incorporating silica fume (SF), metakaolin (MK), fly ash (FA) and blends of FA and MK and to assess the effects of such pozzolans on freeze-thaw durability, air void system and microstructure of hardened concrete. Cement was partially replaced by various quantities of the pozzolanic materials. The results demonstrated that the increase in workability attributed to the air-entraining admixture was greater in MK concrete than in SF concrete and occurred for a greater range of dosages of the admixture. Improvements in workability due to the air-entraining admixture were also obtained in concretes with low levels (20%) of FA. Concretes with 30 and 40% FA although more workable, accrued no such benefit. In addition, the workability of FA-MK concrete was substantially reduced with increasing MK level at all total replacement levels, i.e. 20, 30 and 40%. Furthermore the air content tests indicated that up to 0.24% air entraining admixture resulted in steady increase in the air content of MK concrete, compared to a limit of 0.12% for SF concrete. Alternatively, FA caused large reductions in the air content of fresh concrete, irrespective of the dosage of the airentraining agent. The freeze-thaw durability was determined on both air-entrained and non air-entrained concretes. Based on a criterion that unsatisfactory resistance to freezing and thawing corresponds to a durability factor (DF) less than 60% or a change in length greater than 200 um/m, all the air-entrained concretes exhibited excellent performance under freeze-thaw conditions irrespective of the MK or FA content. On the other hand the non air-entrained concretes performed poorly under freezing and thawing. Thus, it would appear that air entrainment is the controlling factor for good freeze-thaw performance and the material effects are less important. However there were indications to suggest that non air-entrained concretes containing MK at low replacement levels (2.5 and 7.5%) could be frost resistant (DF > 80%). This was attributed to the increased spacing factor effected by the presence of fine particles of MK. Air entrainment was also a key factor for good scaling resistance. For instance, non air-entrained concretes with high replacement levels of MK (7.5 and 10% MK) exhibited more scaling than concretes with low replacement levels (2.5% MK), whereas scaling of air-entrained MK concretes was independent of the replacement level. The concrete containing high amounts of FA (30%) exhibited more scaling than the control and 10% FA concrete. However, blending FA with MK (MK/FA = 1/3) at total replacement levels of 10 and 30% improves the scaling resistance of the resulting concrete as compared to the FA only concrete. Non air-entrained concretes containing FA or blends of FA with MK showed an increase in weight at the beginning of freezing and thawing, an indication of uptake of water. Water absorption results confirmed that this was a result of a more open porosity. There is a strong correlation between sorptivity and pore refinement. Increasing amounts of the MK appear to cause refinemenent of the concrete's pore structure. As a result of this pore refinement sorptivity decreases with increasing amounts of MK. In addition blending FA with MK causes pore refinement. Irrespective of the pozzolanic material or blends of materials used the presence of entrained air appears to have a negative effect on pore refinement.

This thesis presents the design and development of an alternative cement called ‘Alkali Pozzolan Cement’ (APC) for ‘integral sustainability’. The term ‘integral sustainability’ is a philosophical concept that implies an integration of not only the aspects related to ecological sustainability, but also those of technological, economic and social sustainability. Accordingly, this research can be considered as engineering as well as philosophical research; hence, mixed research methods were adopted to achieve the research objectives.

Orientador: Jorge Luis Akasaki
Banca: Marco Antonio Moraes Alcantara
Banca: Antônio Alberto Nepomuceno
Resumo: O presente trabalho apresenta um método de produção de cinza de casca de arroz (CCA) altamente reativa e de coloração clara, bem como o seu comportamento em matrizes de cimento Portland com o intuito de avaliar a atividade pozolânica da CCA. O trabalho está dividido em quatro etapas, a saber: construção de um forno e produção da cinza de casca de arroz, caracterização físico-química da CCA, verificação da atividade pozolânica do material através de métodos instrumentais e, finalmente, ensaios mecânicos em argamassas de cimento Portland. O forno utilizado para a produção da cinza de casca de arroz não apresenta controle de temperatura e, o tempo de queima é bastante longo, aproximadamente 36 horas. Neste método obtém-se cerca de 1,5Kg de cinza por processo de queima. A cinza obtida apresenta uma coloração clara e o seu caráter amorfo foi determinado através de diferentes métodos: difração de Raio-X, determinação do teor de sílica amorfa, análise termogravimétrica, Microscopia Eletrônica de Varredura (MEV) e ensaios mecânicos em argamassas de cimento Portland. O programa experimental também abrange estudos de variação da finura da CCA e estudos com diferentes porcentagens, em substituição ao cimento Portland. Os resultados obtidos foram comparados... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This research show a method of production white amorphous Rice Husk Ash (RHA), therefore, the behaviour of RHA in Portland cement matrix to evaluate the pozzolanic activity of this material. The research can be shared in four steps, to know: construction of an oven and production of rice husk ash, physical-chemical analysis of the rice husk ash, evaluation of pozzolanic activity of the pozzolan though instrumental analysis and, finally, mechanical properties of Portland cement mortars. The oven used for production of rice husk ash didn't have a control of temperature and, the time of burning is so longer, approximately 36 hours. In this method is obtained for about 1,5Kg of ash. The obtained ash has white colour and its amorphous phase were determined though different methods: X-ray diffractometry, determination of amorphous silica, Termogravimetric Analysis (TA), scanning electron microscopy (SEM) and mechanical properties of Portland cement mortars. Besides that, the experimental procedure involves studies on fineness variation of rice husk ash and different degrees of Portland cement substitution. The obtained results were compared with silica fume, because this is the most similar pozzolanic material with rice husk ash. The RHA produced under this method can be used... (Complete abstract click electronic access below)
Mestre

Many of the waste materials produced from modem heavy industries are pozzalans, which develop cementitious properties when finely divided in the presence of free lime. This property allows a potential industrial use for this waste as a cement replacement material in concrete. An example of such a waste material is blast furnace slag from the smelting of iron and steel. The US produces 26 million tons of blast furnace slag annually. Most of the slag is slowly cooled in air and it makes a poor pozzolan. Only 1.6 million tons of the slag is available in the granulated form, which is suitable as a cementitious and pozzolanic admixture. Most European countries are well endowed with coal-fired power stations and this produces fly and bottom ash, flue gas desulphurisation (FGD) gypsum. However, less than 25% of the total ash from power stations has found an industrial use mainly in cement and concrete industry. This creates a massive waste-disposal problem. Disposal of unused fly ash in open tips and ponds, for example, creates pollution problems since the drainage of effluents from the ash in the deposit ponds threaten water supplies by polluting the ground water with traces of toxic chemicals. Recent research has concentrated on the alkali activation of waste pozzolanic materials, especially ground blast furnace slag. This thesis has investigated the alkali activation of low calcium fly ashes. These form very poor pozzolans and the alkali activation of the fly ash offers the opportunity for the large scale use of fly ash. Water glass was selected as a suitable activator for the fly ash. A comprehensive series of tests have been carried out to gain information on the effect of different parameters, such as proportion and composition of the constituent materials, curing conditions and casting methods, in developing high performance construction materials. Laboratory investigations were carried out to determine the following characteristics of alkali activated materials: density, water absorption, apparent porosity and coefficient of saturation, drying shrinkage, compressive creep, compressive, flexural and tensile splitting strength, dynamic modulus of elasticity, accelerated weathering (freeze-thaw cycle) resistance, fire resistance (temperatures up to 600°C), microstructure, macrostructure and investigation of hydration phases by SEM, ED AX, Digital-mapping and X-ray diffraction. The influence of key parameters e.g. slag content, curing method, water/binder ratio and water glass hardener content on the mechanical properties were determined. Optimisation of the alkali-activation of fly ash materials was achieved by blending this with other pozzolans such as silica fume and slags. Mechanical properties were further improved by using moulding pressures and by thermal treatment. The use of short fibre reinforcements was investigated to overcome microcracking, volumetric deformation and creep in the materials. The free shrinkage and creep of the materials agree with the model developed by Mangat and Azari for fibre reinforced Portland cement composites. Other additives were also investigated to improve workability, frost and water resistance and physical properties of the alkali activated materials. The fundamental relationships between chemical composition, hydration phases,microstructure and engineering properties (strength, durability and stability) of alkali activated materials were investigated. It is clear that strength development is a function of the hydration products developed and these are affected by the mix composition and the curing temperature. The current work found parameters such as the Si/Al ratio, the Ca/Si ratio and the Na20 content to be important. These chemical parameters decide the principal phases in the hydration products formed in alkali activated materials, between calcium silicate hydrate (C-S-H) and zeolite of the form (R[2]0 n Al[2]O[3] x SiO[2] r H[2]O).Overall the thesis shows the great potential of alkali activated materials to produce high strength construction materials. Limitation in the shrinkage of the materials can be overcome by the use of fibre reinforcement. At the end of the thesis limitations and suggestions for further work are made.

The challenge for the civil engineering community in the near future will be to realize the building of structures in harmony with the concept of sustainable development, through the use of high performance materials which have low environmental impact and can be produced at reasonable cost. Geopolymers are novel binder materials that could provide a route towards this objective. Although research on geopolymer has advanced, most of the previous research conducted on geopolymers has dealt with pastes and concentrated on the material's chemistry and microstructure. There is little information available concerning the engineering and durability properties of geopolymer concrete and none considering the use of natural pozzolans for production of geopolymer concrete. This investigation has studied the potential of using five natural pozzolans from Iran as geopolymer precursors. Most of the raw materials contain zeolites and clay minerals and have a high loss on ignition. Therefore, trials were made where samples were calcined at 700, 800 and 900°C. The solubility of both the raw and calcined materials in an alkaline solution was used as an indicator for pozzolanic activity. Improvements in pozzolanic properties due to heat treatment and elevated curing temperatures (20, 40, 60, and 80°C) were studied by using alkali solubility, XRD and compressive strength tests. It has been found that geopolymer binders can be synthesized by activating natural pozzolans and condensing them with sodium silicate in a highly alkaline environment. A new model is presented which allows the prediction of the alkali activated pozzolan strength from information on their crystallinity, chemical compositions and alkali solubility. Two types of Iranian natural pozzolans, namely Taftan which can be activated without calcination and Shahindej which was calcined were selected for further activation to study the effect of the alkaline medium on the strength of the alkali-activated natural pozzolan. The effect of the type, form, and concentration (molarities =2.5, 5.0, 7.5, 10.0 M) of the alkaline hydroxide, the modulus of sodium silicate (Si02INa20 ratio =2.1, 2.4, 3.1) and different curing conditions on the geopolymerisation of the above two natural pozzolans were studied. The optimum range and contributions for each factor is suggested based on their effect on compressive strength. An optimum paste formulation has been developed for concrete mixing together with the procedure of addition of the raw materials to the reaction mixture and suitable curing methods for producing the geopolymer concrete derived from them. The properties of this geopolymer concrete in both the fresh and hardened states have been investigated in terms of setting time, workability, air content, compressive strength, splitting tensile strength, static modulus of elasticity, ultrasonic pulse velocity, and drying shrinkage. Studies related to durability such as gas permeability, chloride ion penetration, and sulphate resistance have been undertaken and compared to these for typical OPC concretes. Some problems were encountered in applying the standard concrete durability tests. In this study attempts have been made to determine the relationships between the different properties of geopolymer concrete with its compressive strength and compared to results for ope concrete, to help to explain the differences between alkali-activated natural pozzolan concrete and ope concrete. In the countries which have large resources of natural pozzolan, geopolymer concrete based on alkali activation of these resources can help decrease the energy consumption and environmental impacts involved in using traditional cement pastes.

Self-consolidating concrete has been described as the most revolutionary development in concrete technology in several decades with the ability to flow freely through closely spaced reinforcements, expel entrapped air and self compact without vibration. Since it was first developed in Japan in the early 1980's, major development in the chemical admixture technology has made SCC more viable. An experimental study was conducted to identify the mechanical properties of SCC by optimizing the use of pozzolanic materials and local aggregates with some proposed statistical models. The research was focused to investigate compressive strength, splitting tensile strength, modulus of elasticity and drying shrinkage behavior of concrete. The results were established experimentally and compared with the available SCC research data based on extensive literature study. Besides the improved mechanical performance, results indicate that the use of pozzolanic materials and local aggregate in SCC is recommended in terms of its cost benefit value.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
A utilizaÃÃo de resÃduos como materiais alternativos tem se mostrado uma soluÃÃo satisfatÃria de acordo com vÃrias pesquisas realizadas. Os produtos da combustÃo do carvÃo mineral (PCCs) sÃo resÃduos que causam impacto ambiental, mas apresentam grande potencial de utilizaÃÃo no setor da construÃÃo civil na produÃÃo de argamassas e concretos. Apresentam elevado teor de sÃlica (SiO2), podendo ser utilizados como pozolanas. Esta pesquisa objetivou verificar a viabilidade da utilizaÃÃo dos produtos da combustÃo do carvÃo mineral em argamassas de assentamento e revestimento. As matÃrias-primas foram caracterizadas quanto aos aspectos fÃsicos, quÃmicos e para os PCCs tambÃm foi avaliada sua pozolanicidade. Foram confeccionadas argamassas de referÃncia e com adiÃÃo de PCCs nos teores de 10, 20, 30, 40 e 50% como substituto parcial do cimento. ApÃs tempos de cura de 7 e 28 dias, foram feitos teste de resistÃncia à traÃÃo na flexÃo e resistÃncia à compressÃo. AlÃm disso, as argamassas foram sujeitas a anÃlises de difraÃÃo de Raios â X, Microscopia EletrÃnica de Varredura, absorÃÃo de Ãgua, determinaÃÃo de Ãndice de vazios e massa especÃfica aparente. Os resultados obtidos mostraram-se compatÃveis quando comparados com os dados da literatura, demonstrando ser viÃvel a aplicaÃÃo dos produtos da combustÃo do carvÃo mineral na indÃstria da construÃÃo civil.
The use of residues as alternative materials has proven successful according to several investigations. Coal combustion products (CCPs) is a residue that causes environmental impact, but it has a great potential for use in civil engineering construction in the production of mortars and concrete. It posesses a high content of silica (SiO2) and so it can be used as pozzolan. This research aimed to verify the viability of adding coal combustion products to mortars for bricklaying and covering. The raw materials were submitted to physical, and chemical characterization. CCPs were also rated according to their pozzolanicity. Reference mortars were prepared, as well as mortars containing 10, 20, 30, 40 and 50% amounts of CCPs as a partial replacement for cement. After curing time of 7 and 28 days, prismatic samples were tested to determine their tensile strength in bending and their compression strength. Moreover, the mortars were subjected to X-ray diffraction, scanning electron microscopy and determination of water absorption, voids and apparent density. The results obtained were consistent with literature data, showing that application of coal combustion products in the construction industry is a viable alternative.

This research project seeks to improve soil properties through experimentation with geotechnical purposes. For this, will be used natural volcanic pozzolana in 5%, 10%, 15% and brick dust in 10% giving it a second reuse. The soil improvement will be analyzed with the proposed additions and its influence on the results. It is concluded that the addition improves the behavior of the soil by decreasing its plasticity index, increases the compaction index and improves the geotechnical parameters.

The use of high performance concrete in construction has been enhanced by the use of pozzolanic materials. However, the use of these materials has not been optimized. Such optimization may be achieved by a systematic increase in the amount and combination of pozzolanic material additions, with accompanying studies of their effects on the mechanical, durability and microstructural characteristics of blended concrete. This work evaluated various concrete durability issues by studying systematic increases of pozzolanic materials such as fly ash and blast furnace slag (BFS) in the range of 25, 50 and 70%, and silica fume at 10% of total cementitious materials, forming various binary and ternary concrete blends. The concrete specimens were cured for a period of seven days after demoulding in line with widely practiced commercial curing procedures. The research explored the role and effectiveness of various binary and ternary blends of pozzolanic materials on the mechanical, durability and microstructural characteristics of concrete. Durability was evaluated by two independent rapid chloride permeability tests measured as charge passed and chloride conductivity from the RCPT and UCT tests respectively. These two rapid tests were coupled with long-term ponding tests to evaluate chloride ingress and the extent of corrosion for a period of two years. Further durability tests such as carbonation, drying shrinkage and porosity of these blends were also undertaken. This study also utilized micro-analytical techniques such as X-ray diffraction and Scanning Electron Microscopy to follow the hydration mechanism in various binary and ternary blends. Statistical significance testing was used to analyse and confirm all experimental results and conclusions. It is well known that a level of caution is exercised in the construction industry in the use of ternary blends. This study aims to evaluate the durability aspects of ternary concrete blends, in addition to binary blends, for resistance to chloride, corrosion, carbonation attacks and provide recommendations relating to the limits of blending level, as well as exposure conditions for blended concretes, based on the results of this study. It is expected that this will fill a major knowledge gap observed in the concrete industry. A comparison of two rapid chloride permeability tests such as UCT and RCPT indicates that the UCT test is easy and practicable, and does not contradict results obtained in the standard RCPT. However, the statistical significance of results obtained for some blends was only able to be established by using the RCPT. This effect can be attributed to the larger size specimens compared to UCT. The recommended blend to acquire both early-age and long-term strength development in fly ash is the ternary blends comprising 10% silica fume and 25% fly ash cast using lower w/b ratio. In addition, the same blend exhibited lower carbonation depth, lower charge passed from RCPT, lower chloride ingress and higher corrosion resistance characteristics from long-term ponding test compared to other blends of fly ash. In BFS blends, an increase in compressive strength was observed only in the specimens of 25% BFS compared to other higher percentage blends, while the higher addition of 50 and 70% replacement showed no significant difference in compressive strength between them and their corresponding ternary blends with addition of silica fume. The results of this study indicate that control (OPC) specimens cast with increased w/b ratio of 0.48 showed higher chloride ingress compared to both binary blends of 70% fly ash and 70% BFS specimens. This indicates that (OPC) cast using higher w/b ratio is to be avoided in chloride environments. On the other hand, though, the ternary blends of 10% silica fume and up to 50% fly ash exhibited lower chloride ingress compared to their respective binary blends of fly ash. However, these ternary blends exhibited lower compressive strength, more negative corrosion potential and higher corrosion rate, compared to the respective binary blends of 25% fly ash and its ternary blends. Therefore, the recommended blend observed in the long-term ponding test is the ternary blend of 25% fly ash and 10% silica fume. The recommended level of corrosion resistance in slag specimens is achieved by the use of ternary blends comprising silica fume at 10% added to the blend that contains up to 70% slag. However, the recommended level of slag for a lower carbonation effect is the use of a ternary blend comprising 50% slag and 10% silica fume (3B5S1) which showed a carbonation depth of 10.8 mm and a compressive strength of 53.2 MPa after 365 days of exposure. The drying shrinkage of concrete increased with the increase in fly ash and the same trend was observed in BFS specimens. However, the results were not significantly different between their respective blends. The extent of carbonation in fly ash specimens was higher compared to BFS blends specimens. This can be attributed to the formation of dusty and weak surfaces on the outer surface in addition to the excessive leaching of sodium chloride solution from the long-term ponding test in the former specimens compared to later. The high volume pozzolanic materials, irrespective of fly ash or BFS and addition of silica fume (70% fly ash and 10% silica fume, and 70% BFS and 10% silica fume), showed higher cumulative pore volume indicating that these blends with seven days of curing were not beneficial. These high volume ternary blends required prolonged curing to release portlandite from the hydration of cement to continue the pozzolanic reaction. This study has shown that 7-days curing of the pozzolanic concrete is inadequate if pozzolanic activity is to be invoked. This is particularly the case when it is expected that the concrete is likely to be subjected to a harsher than usual environment characterised by a dry atmosphere.

Perlite is a volcanic glass which has high amount of silica and alumina. Those properties make it a candidate, if finely ground, for being used as a pozzolan. The studies on the pozzolanic properties of perlite are very limited, and none of them has dealt with the use of perlite in the blended cement production. The aim of this study is to investigate the pozzolanic properties of perlite, and if appropriate to investigate perlite&rsquo
s usability in blended cement production. For this purpose, perlites from two different sources &ndash
Izmir and Erzincan - are used as replacement of portland cement clinker with two different percentages: 20% and 30% by weight of total cement. Then for each different composition, materials are ground with some gypsum in order obtain grinding curves for the resultant cements. After obtaining the grinding curves, a total of 22 cements with two different finenesses are produced by intergrinding and separately grinding the materials for each composition. The obtained cements are used in paste and mortar production so that normal consistencies, setting times, autoclave expansions, and compressive strengths are determined.

Cement is the main ingredient in concrete, and the production of cement is a costly and energy absorbing process. In addition, production of cement ominously contributes to environmental pollution, as 1 ton of cement releases about 0.9 ton of CO2 in the atmosphere. Since cement is the material which is primarily responsible for the cost and the pollution, there is a critical need to develop materials which exhibit cementitious property and could be used as a substitute of cement. Supplementary Cementitious Materials (SCM), are substances which possess cementitious properties, hence they can be used as a partial/total replacement of cement. Recently, use of recycled material, such as waste glass powder (WGP), has received augmented attention in the concrete industry. At first, waste glass was used as an aggregate replacement in concrete and it was observed that the mechanical and durability properties of the modified concrete were degraded due to the increased potential of Alkali-Silica Reaction (ASR). Later, literature studies have shown that ASR occurrence in concrete is dependent on the particle size distribution of the glass used. As the particle size decreases the ASR probability reduces. These results motivated the use of recycled glass powder (RGP) with microscopic particle size distribution as cement replacement. There are multiple benefits of using RGP as cement replacement: firstly, using a waste material would reduce the load on the landfills, secondly, the total cost would be less as recycled WGP is replacing the costly cement; and finally, the use of RGP would lead to sustainable construction as a consequence of a decrease in cement manufacturing. The present study deals with the experimental investigation on RGP as a pozzolanic cement. The Glass Powder (GP) used in this experiment was provided by the Australian company, Enviro Sand who supplied samples with two particle sizes of 75 μm and 150 μm for the purpose of this research. The main aim of this research project is to study the pozzolanic performance of GP having a particle size smaller than 150 μm. The current study involves an extensive experimental program which includes: density, compressive strength, tensile strength, pozzolanic activity, water absorption, chloride resistance, heat of hydration and drying shrinkage. Extensive concrete specimens of standard cube, cylinder and rectangular prism of standard dimensions are prepared to investigate the various material, strength and durability properties by varying the GP content. In addition, present experimental work consists of enhancing the pozzolanic performance of the GP by varying the curing conditions and modifying the mix design. In total, about 700 specimens were tested in three stages in this experimental research work The optimisations resulted in Strength Activity Index (SAI) of coarse GP which was comparable to the SAI values of much fine GP reported by the earlier published research works. Since a considerable amount of energy would be consumed in grinding the glass from coarse to fine, the grinding energy would in turn lead to increment in the cost and rise in harmful carbon di oxide emissions. The current research is significant owing to the multiple benefits mentioned in the previous paragraph, furthermore, locally, according to a recent report from Australian National Waste, Australia generates around 1.1 million tonnes of glass waste which is equivalent to about 45 kg glass per capita and approximately 44% of it is landfilled. This practice of dumping the glass waste in landfills is environmentally unsustainable, since glass is non bio-degradable in nature. The last stage mix design alteration resulted in a maximum SAI of 117%. In addition, it resulted in higher resistance to chloride ion penetration of 17% and about 23% lower heat of hydration than the control mix at 30% replacement of the coarse GP.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
Full Text

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Doyoyo Mulalo; Committee Member: Will Kenneth; Committee Member: Yavari Arash. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Portland cement hydration is an exothermic process. The heat evolved during the hydration process is especially important in mass concrete, and hot and cold weather concreting. Heat of hydration is affected by several factors like chemical composition of cement, fineness of cement and ambient temperature. The major aim of this thesis is to investigate the effect of cement composition and fineness, amount and composition of the fine portion (<
45 µ
m) of natural pozzolan-incorporated cement on hydration heat. For this purpose, a portland cement and pozzolan-incorporated blended cements containing different amounts of natural pozzolan (trass) were used. The heat of hydration was measured using isothermal calorimetry. The values of heat of hydration for mixtures with different finenesses containing different amounts of added pozzolan were determined. The results obtained were used to find a correlation between the fineness, composition of cement and heat of hydration. According to this study, pozzolan incorporation in small amounts accelerates hydration. A similar effect was obtained for higher pozzolan amounts. Finer cements react faster and result in higher amounts of early heat evolved compared to coarser cements. In addition, it was found that the sum of the heat of hydration values of fine and coarse portion of cements was less than the total heat of hydration of blended cements. Moreover, a satisfactory correlation could not be established between results of isothermal calorimetry, and adiabatic calorimetry, setting time, and strength.

The use of lime mortars with pozzolanic additives is of special importance for the repair of historic masonry. In this study, the effect of pozzolanic materials on the final characteristics of mortars was investigated. Metakaolin, fly ash and historic brick powder were used as pozzolanic materials in mortar mixes with varying binder:pozzolan:aggregate ratios. Historic mortar samples from rubble stone masonry of Kahta Castle, a medieval structure in close vicinity of the Nemrut Dag Monument, were also investigated to serve as a starting point for the preparation of repair mortars. Physical and physicomechanical tests, optical microscopy, chemical tests, SEM-EDX and XRD analyses were used to assess the properties of the historic mortars and repair mortars. Fat lime was found to be used in historic mortars with a high binder/aggregate ratio. They were observed to have relatively low density and high porosity with an average compressive strength of 7.4 MPa. Historic mortars were determined to have relatively high water vapour permeability and low water impermeability characteristics. In repair mortars setting was found to be predominantly due to carbonation along with pozzolanic reactions. However, abundant presence of stratlingite in mortars with added metakaolin indicated that the pozzolanic reactions preceded carbonation in those mortars. Use of pozzolanic materials increased the uniaxial compressive strength and modulus of elasticity of mortars compared with control samples. Using the same binder:pozzolan:aggregate ratio, highest increase was observed on mortars prepared with added fly ash at the end of 90 days. Durability parameters of repair mortars defined as wet to dry compressive strength were in the very good to excellent range according to Winkler&rsquo
s classification. By using fly ash, design of lime mortars with high water impermeability and high water vapour permeability characteristics was accomplished.

L’incorporation de sous-produits agricoles ou de matériaux naturels dans la matrice cimentaire confère des propriétés intéressantes aux composites élaborés. L’objectif de cette thèse est d’élaborer un matériau pouvant répondre aux exigences mécaniques, thermiques et de durabilité des matériaux de construction en zone tropicale humide. Dans un premier temps, l’activité pouzzolanique d’une pouzzolane naturelle, de cendres de tronc de bambou et de cendres de bagasse de canne à sucre ont été évaluées. L’influence de leur incorporation a été ensuite étudiée sur les propriétés mécaniques et la durabilité des mortiers exposés à des ions chlorures et sulfates. Dans un second temps, l’influence de l’ajout de fibres de bagasse sur les propriétés thermiques et mécaniques des composites a été étudiée en fonction de différents paramètres (teneur en fibres, environnement de vieillissement, type de matrice cimentaire).Les résultats obtenus ont permis de montrer que les matériaux étudiés possèdent une activité pouzzolanique et qu’il est possible de les incorporer au ciment afin de lutter contre la corrosion. De plus, les composites élaborés avec des fibres de bagasse sont plus isolants que ceux élaborés sans fibres. Cependant, du point de vue des propriétés mécaniques, l’incorporation de fibres de bagasse diminue les contraintes à la flexion des composites
The incorporation of crop wastes or natural materials in the cement matrix confers interesting properties to composites prepared. The aim of this thesis is to develop a material that can reach the mechanical, thermal and durability requirements for building materials in the humid tropical zone. Firstly, pozzolanic activity of a natural pozzolan, bamboo stem and sugar cane bagasse ashes has been determined. Influence of their incorporation on mechanical properties and durability of mortars exposed to chloride and sulphate ions was studied. Secondly, influence of addition of bagasse fibers on thermal and mechanical properties of composites was studied as a function of various parameters (fibers content, curing, type of cement matrix).These results has shown that the materials studied have pozzolanic activity and it is possible to incorporate them into the cement to fight against corrosion. Moreover, composites elaborated with bagasse fibers are more insulating than those elaborated without fibers. However, from the viewpoint of mechanical properties, incorporation of bagasse fibers decreases flexural strength of composites in the present work and under the conditions producing procedures that were adopted

Perlite is a glassy volcanic rock that contains approximately 70-75% silica and 12-18% alumina. There are very large perlite reserves in the world (~6700 million tons) and approximately two thirds of these is in Turkey. Due to its high amounts of silica and alumina, at the beginning of such a study, it seemed that it would be worth first to find out whether perlite possesses sufficient pozzolanic property when it is a finely divided form and then to investigate whether it could be used as a pozzolanic addition in producing blended cements. In this study, perlites from two different regions (izmir and Erzincan) were tested for their pozzolanic properties. After obtaining satisfactory results, grindability properties of the clinker, perlites and their different combinations were investigated. Several blended cements with different fineness values and different perlite amounts were produced by either intergrinding or separate grinding methods. The tests performed on the cement pastes and mortars containing the blended cements produced were as follows: Water requirement, normal consistency, setting time, soundness, compressive strength, rapid chloride permeability, resistance to sulfate attack and resistance to alkali-silica reactions. The results showed that Turkish perlites possess sufficient pozzolanic characteristics to be used in cement and concrete industry. Moreover, the properties tested in this study satisfied the requirements stated in the standards for blended cements. The durability of the mortars was found to be improved by 20% or more perlite incorporation.

Portland cement manufacturing process consumes large amount of natural resources and generates approximately 5% of global CO2 emissions. Consequently, alternative approaches for CO2 reduction are an important cement industry focus. The present project revisits lime-­‐pozzolan systems, as a modern approach to sustainable cement technology. The idea of the partial calcination of limestone to produce core-­‐shell like lime for blending with pozzolan is proposed. The partial calcination of limestone has been studied in an experimental fluidised bed reactor. The calcination conditions, including residence time, temperature, air flow rate and particle size of limestone, have a significant influence on the kinetics of the decomposition reaction and subsequent properties of the partially calcined limestone. The porous CaO shell on a limestone particle can provide the same reactivity as a fully calcined particle except that only the activated portion is available for reaction, the unreacted core remaining as a micro-­‐aggregate in matrices of C-­‐S-­‐H. The performance test demonstrates that a blend of partially calcined limestone and rice husk ash produced in the FBR provides sufficient compressive strength, workability, water retentivity and durability for use as plastering and masonry mortar. The coated Ca(OH)2 shell on a limestone particle exhibits an advantage in the fresh mortar properties such as workability and water retention. The sustainability assessment proves that CO2 emissions and the thermal energy consumption for the production of partially calcined limestone – pozzolan mortar is lower than those of conventional mortar.

Numerous agents and mechanisms are known to affect the durability of a concrete structure during its service life. Examples include freezing and thawing, corrosion of reinforcing steel, alkali-aggregate reactions, sulfate attack, carbonation, and leaching by neutral or acidic ground waters. Among these, external sulfate attack was first identified in 1908, and led to the discovery of sulfate resistant Portland cement (SRPC). Besides SRPC, another way of coping with the problem of sulfate attack is the use of pozzolans either as an admixture to concrete or in the form of blended cements This study presents an investigation on the sulfate resistance of blended cements containing different amounts of natural pozzolan and/or low-lime fly ash compared to ordinary Portland cement and sulfate resistant Portland cement. Within the scope of this study, an ordinary Portland cement (OPC) and five different blended cements were produced with different proportions of clinker, natural pozzolan, low-lime fly ash and limestone. For comparison, a sulfate resistant Portland cement (SRPC) with a different clinker was also obtained. For each cement, two different mixtures with the water/cement (w/c) ratios of 0.485 and 0.560 were prepared in order to observe the effect of permeability controlled by water/cement ratio. The performance of cements was observed by exposing the prepared 25x25x285 mm prismatic mortar specimens to 5% Na2SO4 solution for 78 weeks and 50mm cubic specimens for 52 weeks. Relative deterioration of the specimens was determined by length, density and ultrasonic pulse velocity change, and strength examination at different ages. It was concluded that depending on the amount and effectiveness of the mineral additives, blended cements were considered to be effective for moderate or high sulfate environments. Moreover, the cement chemistry and w/c ratio of mortars were the two parameters affecting the performance of mortars against an attack. As a result of this experimental study it was found out that time to failure is decreasing with the increasing w/c ratio and the effect of w/c ratio was more important for low sulfate resistant cements with higher C3A amounts when compared to high sulfate resistant cements with lower C3A amounts.

Concrete is an integral material in modern infrastructural requirements worldwide. The production of Portland cement is however expensive, energy intensive, and results in globally significant greenhouse gas emissions. Natural pozzolans such as pumice can be used as a partial replacement for Portland cement in concrete, which can reduce production costs and greenhouse gas emissions, and improve concrete performance. A fluvial pumice deposit which may be suited for use as a natural pozzolan has been identified on the floodplains of the Waikato River. A sample was milled in Germany, and returned to New Zealand in two subsamples. These were tested in concrete, with tests divided into four rounds. The first two rounds established baseline concrete strengths at water/binder (w/b) ratios of 0.6 and 0.5, with pumice replacing cement at 5, 10, 15 and 30%. Round Three assessed the use of high pH mix water (pH=12.9), and Round Four assessed the use of a polycarboxylate superplasticiser, both with 10% pumice. Pumice is known to retard early concrete strength, however through optimisation of mix design, improvements in concrete strength and durability can be made. Indeed, all 28 day concrete strengths in this research were below Ultracem, however half of these achieved or exceeded Ultracem strengths at 91 days. The use of superplasticiser achieved the best 28 day concrete strengths, and dosage optimisation is expected to yield further improvements. Concrete durability was tested at w/b=0.5, with 10% and 30% pumice. After prolonged curing (231 days), composite concrete showed substantial improvements in electrical resistivity and resistance to chloride attack, most notably with 30% pumice. Concrete porosity was essentially unaffected. This pumice has shown significant promise as a partial cement replacement. Further mix optimisation is likely to yield greater improvements in concrete strength and durability, and will provide a more economically and environmentally sustainable product for the New Zealand concrete market.

Calcium aluminate cement (CAC) is used as a protective lining to combat attack by microorganisms and their metabolic products on reinforced concrete sewer pipes. CAC corrosion behaviour is related to the conversion process of the aluminate hydrates. Full conversion can result to a 5-8 times increase in corrosion rate. Hence, understanding and controlling the rate and the processes that affect conversion is important in the effective use of CAC as a mitigation strategy against the attack of microorganisms. This study was focussed on the role of the pozzolanic material, i.e. fly ash, in suppressing the conversion of CAC. CAC mortars were prepared with constant water-cement ratio of 0.4 and with fly ash contents of 0%, 5%, and 25% weight. To assess the effectiveness of the fly ash, CAC mortars were cured at high temperatures (80-100oC) in water bath to accelerate conversion. Thermal analysis (TGA), X-Ray diffraction (XRD), and scanning electron microscopy (SEM) with integrated EDS and EBSD system were used to monitor the physical and mineralogical transformation of CAC during the conversion and leaching tests. Our study showed that pozzolanic materials have negative and positive impacts in CAC. Based on thickness loss, addition of fly ash improved the corrosion resistance of CAC. This can be attributed to the increased formation of the stratlingite (C2ASH8) that was found to be resistant to both organic and mineral acids. However, analysis based on weight loss and dissolved Al metal showed that addition of fly ash suppresses early corrosion but later corrosion is increased, which is attributed to greater formation of C3AH6 and greater porosity.

This research uses a novel construction material (lime-pozzolan concrete) and real-world project (a school) as a vehicle for investigating the implementation or applied-innovation process in construction. The implementation of new technologies at a product-level is recognised to be an antecedent of technological change in the construction industry. A ‘real world’ construction project aiming to implement a novel lime-pozzolan concrete in the field, has been used as a process-tracing case study. Rigorous analysis of this case study project, expressly focusing on project-level communication, has shown the implementation of innovative and sustainable materials to be a complex, socio-technical process. With the aim of identifying opportunities to improve project-level design processes in order to support the uptake of innovation and sustainable solutions, twelve high-level theories have been built on twenty-five emergent themes. Collectively these insights demonstrate that implementation processes, once initiated, are experiential, social, contextual, active, interactive, temporal, intentional and mutually constituted phenomena. On the strength of empirical findings this thesis argues for a radical shift in managerial attention from the outcome of the process to the process itself; specifically focused on the experience of the design team as process participants. Laboratory testing and initial field trials have demonstrated the technical feasibility of producing structural grade lime-pozzolan concretes with 28-day compressive strengths of up to 50MPa. The lime-pozzolan concretes were ternary combinations of hydraulic lime (NHL5), ground granulated blastfurnace slag (GGBS) and silica fume (SF). The use of NHL5 in conjunction with pozzolanic materials has been shown to be a viable ‘low-carbon’ alternative to CEMI or CEMIII/A in certain circumstances, although this work has demonstrated that the potential savings in the embodied CO2 and energy of lime-pozzolan concretes are highly dependent on the boundaries of the analysis. Moreover the potential for lime-pozzolan concrete with a lower still CO2 and energy intensity than any concretes tested to date has been identified.

High-performance concrete is defined as concrete that meets special combinations of performance and uniformity requirements that cannot always be achieved routinely using conventional constituents and normal mixing, placing, and curing practices. Ever since the term high-performance concrete was introduced into the industry, it had widely used in large-scale concrete construction that demands high strength, high flowability, and high durability. A high-strength concrete is always a high-performance concrete, but a high-performance concrete is not always a high-strength concrete. Durable concrete Specifying a high-strength concrete does not ensure that a durable concrete will be achieved. It is very difficult to get a product which simultaneously fulfill all of the properties. So the different pozzolanic materials like Ground Granulated Blast furnace Slag (GGBS), silica fume, Rice husk ash, Fly ash, High Reactive Metakaolin, are some of the pozzolanic materials which can be used in concrete as partial replacement of cement, which are very essential ingredients to produce high performance concrete. So we have performed XRD tests of these above mentioned materials to know the variation of different constituent within it. Also it is very important to maintain the water cement ratio within the minimal range, for that we have to use the water reducing admixture i.e superplasticizer, which plays an important role for the production of high performance concrete. So we herein the project have tested on different materials like rice husk ash, Ground granulated blast furnace slag, silica fume to obtain the desired needs. Also X-ray diffraction test was conducted on different pozzolanic material used to analyse their content ingredients. We used synthetic fiber (i.e Recron fibe) in different percentage i.e 0.0%, 0.1%, 0.2%, 0.3% to that of total weight of concrete and casting was done. Finally we used different percentage of silica fume with the replacement of cement keeping constant fiber content and concrete was casted. In our study it was used two types of cement, Portland slag cement and ordinary Portland cement. We prepared mortar, cubes, cylinder, prism and finally compressive test, splitting test, flexural test are conducted. Finally porosity and permeability test conducted. Also to obtain such performances that cannot be obtained from conventional concrete and by the current method, a large number of trial mixes are required to select the desired combination of materials that meets special performance.

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.

Dissertação de mestrado integrado em Engenharia Civil
A indústria do betão gera alguns problemas ambientais e de sustentabilidade associados à incorporação do Cimento Portland, cujo fabrico é, conforme sabido, altamente consumidor de energia e é responsável por cerca de 7% das emissões de CO2 para a atmosfera. As adições minerais Pozolânicas permitem substituir o Cimento, contribuindo com uma quantidade adicional de silicatos de cálcio hidratado (CSH). Para a formação do CSH adicional a pozolana tem de reagir com o hidróxido de cálcio proveniente da hidratação do Cimento, originando a reação pozolânica. Por vezes, para dosagens elevadas de adições minerais, o hidróxido de cálcio pode ser insuficiente para o bom funcionamento da reação pozolânica, situação em que pode ser necessária a sua adição. Esta reação, geralmente, produz uma redução da porosidade do betão, aferindo ao betão maior durabilidade. Esta substituição apresenta inúmeros benefícios, tanto em relação à reologia no estado fresco quanto ao comportamento mecânico no estado endurecido. Neste contexto, desenvolveu-se este trabalho tendo como principal objetivo estudar a incorporação de cal em misturas cimentícias com elevados teores de adições minerais. Concretamente pretende-se analisar o efeito da incorporação de cal como potencial ativador da reação pozolânica em misturas com quantidades reduzidas de Cimento. Adicionalmente, pretende-se, também, determinar se a adição de cal permite, ou não, dotar a composição de uma maior reserva alcalina e, assim, melhorar a sua resistência à carbonatação. Para isto, realizaram-se doze tipos de composições cimentícias com dois tipos de matriz ligante, Cimento e Cinzas volantes; e Cimento, Cinzas volantes e Metacaulino. Em todas as composições, a quantidade de substituição de Cimento por adições minerais foi de, pelo menos, 60%. Para cada um destes dois tipos de matrizes cimentícias fez-se variar o teor de cal entre 0 e 25%. Neste trabalho experimental, para a mistura ternária, observou-se uma melhoria na resistência à compressão e à carbonatação para as misturas com incorporação de cal até 15%. Esta tendência foi acompanhada nas misturas com Cimento e Cinzas volantes, onde a resistência à compressão, perto da ultima data de ensaio (90 dias), aumentou relativamente à da amostra Padrão para um teor de Cal de 5% e a resistência à Carbonatação foi melhorada independentemente do teor de cal adicionada.
The concrete industry generates some environmental and sustainability issues associated with the incorporation of Portland cement, whose manufacture is, as well known, highly energy consumer and responsible for about 7% of CO2 emissions into the atmosphere. The Pozzolanic mineral additions allow substitute the cement, contributing with an additional amount of hydrated calcium silicate (CSH). For the formation of the additional CSH, the pozzolan must react with the calcium hydroxide from the hydration of the cement, resulting in the pozzolanic reaction. Sometimes, for high dosages of mineral additions, calcium hydroxide may be insufficient for proper functioning of the pozzolanic reaction, situation in which may be necessary its addition. This reaction, usually, produces a decrease in the porosity of the concrete, assessing the concrete a bigger durability. This substitution has many benefits, for the rheology in fresh state as well as the mechanical behavior in the hardened state. In this context, this work was developed with the main objective of studying the incorporation of lime in cementitious mixtures containing large amounts of mineral additions. Specifically, it is intended to analyze the effect of the incorporation of lime as a potential activator of the pozzolanic reaction in mixtures with small quantities of cement. Additionally, the aim was also to determine whether the addition of lime allows, or not, to give the composition an increased alkalinity and thus improve its resistance to carbonation. With this purpose, there were made twelve types of cementitious compositions with two types of matrix binder, Cement and fly ash, and cement, fly ash and Metakaolin. In all compositions, the amount of cement replacement by mineral additions was, at least, 60%. For each of these two types of cementitious matrixes was used a variation of the content of lime between 0 and 25%. In this experimental work, for the ternary blend, we observed an improvement in the resistance to the compressive strength and the carbonation for the blends incorporating lime up to 15%. This tendency was accompanied in mixtures with cement and fly ash, where the compression resistance near the last day of the test (90 days) increased compared to that of the standard sample for a content of 5% of lime, and the resistance to carbonation was improved independently of the amount of lime added.

博士
國立臺灣科技大學
營建工程系
103
Limestone which produces lime is available in large quantities in many parts of the world. Continuous formation through the deposit of shells and skeletons of land and marine animals and organisms ensures that it will always be available and is thus a sustainable material. On the other hand, fly ash and silica fume are ready-to-use industrial wastes produced respectively during the burning of coal and in the manufacture of silicon and its alloys. These materials are ideal for the production of cement for the construction industry. Lower burning temperatures of lime compared with Portland cement and the ability to blend with larger amounts of pozzolana reduce the consumption of energy and natural raw materials and the emission of CO2 during cement production, thereby making cement greener. However, low early strength has been a setback for the use of lime-pozzolana cement. This study attempts to produce lime-pozzolana paste of high strength and explores the effects of powder proportions, water-binder ratio, fineness of lime, curing conditions, and pre-soaking lime on the early strength of paste made from non-hydraulic lime, type F fly ash, and silica fume. Paste with 28-day strength of 35 MPa is obtained. The consumption of raw materials and energy and emission of CO2 are reduced by factors of 2.6, 2.7, and 2.5, respectively compared with Portland cement. However, tests show that at early ages, lime-pozzolana paste is porous and potentially less durable and prone to leaching. This setback can be mitigated by covering lime-pozzolana concrete with impervious coating after water curing.

碩士
國立中興大學
土木工程學系所
99
The purpose of this research is to investigate the shear behavior of reinforced concrete beams with the addition of pozzolans. A total of 20 beam specimens were fabricated in this study. All beam specimens were designed without shear reinforcement. The compressive strength of concrete in 10 of the beams was 31.30 MPa, and that in the other 10 was 51.00 MPa. Four substitute ratios of cement with slag(5 %,10 %,15 %,and 20 %), four substitute ratios of sand with fly ash(5 %,10 %,15 %,and 20 %), two substitute ratios of cement with silica fume(2.5 %,5 %), were used for each concrete strength. The test variables include concrete strength and the addition of pozzolans. (1)The cracking shear strength, ultimate shear strength, member stiffness, and crack control capability, increase with the concrete strength; but the shear ductility decreases with the concrete strength. (2)The influence of slag replacement on the cracking shear strength, ultimate shear strength, member stiffness, crack control capability, and shear ductility, is unapparent; however the cracking shear strength increases with the replacement of slag in low-strength concrete beams. (3)The cracking shear strength, ultimate shear strength, member stiffness, and crack control capability, decrease with the fly ash replacement; moreover, this phenomenon is more significant on the ultimate shear strength. (4)The cracking shear strength, ultimate shear strength, and crack control capability, increase with the silica fume replacement; but this phenomenon is not significant on the member stiffness. (5)Use of ACI code procedure to calculate λ is not conservative.

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.

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.

碩士
國立臺灣科技大學
營建工程技術學系
84
The electrical property of concrete is the crucial factor for its corrosion behavior. In the previous study of the electrcal to the performance of concrete. Test parameters are admixtures of fly ash, silica fume and blast furnace slag, different paste mixture proportion, and curing condition with different temperatures and humidities based on same W/B and paste amount. The change of specimen rrsistivity, compressive strength, MIP, SEM, permeability, pH volume and C- content are studied to understand the relationship and the electrical distinction between the concrete with or without pozzolans. Regarding the densified mixture proportion algorithm, the cement volume can be minimized and the ultimate strength will not be affected. About electrical property of concrete, if the specimen is ccured under the environment with higher relative humidity, the resistivity of the specimen will be lower than that under lower relative humidity although the inner part of concrete appears more pore solution with electrical conductivity. All above is due to the more complete hydration reaction which could densify the microstructure Besides, owing to the addition of Pozzolans, the resistances of concrete and mortar increase a lot, especially that with the addition of silica fume.

Concerns over the future availability of traditional SCM sources, such as fly ash, have left the concrete industry in need of alternative sources of SCMs. The research presented here has evaluated natural pozzolans such as pumice, perlite, vitric ash, zeolites, shale and calcined clay as alternative sources of SCMs. Unlike previous research that has only concentrated on empirically evaluating the performance of natural pozzolans in concrete, the research presented in this dissertation has measured both the performance of the pozzolans in cementitious mixtures as well as their physical and chemical characteristics, to draw meaningful relationships between pozzolan properties and performance. The physical and chemical characteristics of these natural SCMs were measured using techniques like particle size analysis, Brunauer–Emmett–Teller (BET) surface area, scanning electron microscope (SEM) imaging, x-ray fluorescence (XRF), x-ray diffraction (XRD), and thermal gravimetric analysis (TGA). The performance of the pozzolans as alternative SCMs was examined by looking at their effect on mortar strength and mixture workability, as well as by their ability to mitigate expansions from durability problems like alkali silica reaction (ASR) and sulfate attack. The performance of the pozzolans was related back to their physical and chemical characteristics to gain an understanding of the underlying mechanisms of cement and pozzolan interaction, and to draw insights as to why some pozzolans perform better than others in cementitious mixtures. Using this knowledge, some of the under-performing pozzolans were modified to see if changes in their properties could improve performance. Results of the research showed that other than the two coarse zeolites, the rest of the pozzolans tested could be used as Class F fly ash replacements in concrete, with the pumice, perlite, metakaolin and fine zeolite being the best performers in terms of mortar strength and durability. Although the pumice mortar had lower strengths than the control at early ages, results from the performance improvement studies showed that the reactivity of pumice could be enhanced by grinding the pozzolans to a finer particle size distribution. Zeolites were found to negatively affect mixture workability, but calcination of the zeolites helped to improve the workability of zeolite mixtures.
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碩士
國立屏東科技大學
土木工程系所
95
Fly ash and furnace slag are the dispose waste both of the fossil power plant and the steel industry. Several researches and experiment show those can be recycled. They can replace the cement as the additive and make the concrete structure more environmental and then reach the economic benefit by recycling them. Because the fly ash and furnace slag have pozzolans’ characteristic, they can not only replace partial cement, but also improve and upgrade the mechanics and physical property. So this research will mainly focus on the different amount of fly ash and furnace slag as the additive, with different W/b ratio different age then explore the variety of properties and the best quantity for replacement of portland cement type II. This research shows the mechanics and physical properties with 6 different additive ratios, 3 different W/b ratios and 4 different ages. The results also show that slag/fly ash ratio(20%/20%) as the replacement with any one W/b ratio will have the best late age(56~91days) strength, the lowest absorption, the good performance both on workability and slump and the best economic benefit.

碩士
國立中興大學
土木工程學系所
95
The purpose of this research is to investigate the effects of adding pozzolanic materials on the hydration characteristics of the cement paste. First, for the conditions of varied experimental parameters including water-to-binder ratios(w/b), pozzolanic material replacements and testing ages, the compressive strength tests, the ignited loss analysis, and the MIP porosity measurements were conducted on three series of pastes— ordinary Portland cement (OPC) paste, fly ash-cement (FC) paste and slag-cement (SC) Paste. Second, the effects of experimental variables on compressive strength, non-evaporable water (wn) content, Ca(OH)2 content, degree of pozzolanic reaction and porosity of the three series of pastes were studied. The interaction existing in these variables was also assessed. Finally, the correlations between the results of each test would be analyzed and canvassed. The correlation formula would be further established according to the obtained experiment data. Test results show that, for all series of pastes, with w/b increasing, wn content, Ca(OH)2 content, degree of pozzolanic reaction, degree of cement reaction, and porosity would increase. However, the compressive strength and the gel/space ratio of the pastes would decrease; For pozzolan-cement pastes, the wn content would decrease with the increase of the percentage of cement replaced by pozzolanic material; For OPC pastes, with the increase of age and w/b, the Ca(OH)2 content would increase, but after 28 days, the raising tendency has gradually slowed down. Nevertheless, the Ca(OH)2 content of FC and SC pastes would decrease with the age and the proportion of replacement increasing; The reaction degree of pozzolanic material is in connection with age and w/b. For the same w/b, the reaction degree of slag (14.7~40.3%) is higher than that of fly ash (3.1~28.3%); The porosity of paste would increase with the increase of pozzolanic material replacement. For lower w/b and replacement level, pozzolanic materials would have the better capability of filling pores; The gel/space ratio would decrease with the increase of the replacement of pozzolanic material. For both FC pastes and SC pastes, at the highest replacement level, the reduced extent of gel/space ratio would be significantly higher than that at the other replacement levels; As for the correlations between total pore volume and either compressive strength or gel/space ratio, OPC pastes possess the optimum correlation coefficients (R2 = 0.9242 & 0.8845).