Дисертації з теми "Replacement for Cement in Concrete"
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1
Darwish, Abdulhanan A. "Development of high performance concrete using combinations of mineral admixtures." Thesis, University of Sheffield, 1995. http://etheses.whiterose.ac.uk/3066/.
Повний текст джерелаАнотація:
Cement replacement materials are by-products used to produce high performance concrete. Published data on the effects of combinations of mineral admixtures in concrete on the microstructural and performance-related properties under different curing regimes are comparatively little. Further the correlation of strength of concrete to its permeability and pore structure is also not clear. The main objective of this research is to study the performance of various combinations of fly ash/silica fume and slag/silica fume concretes under three different curing regimes, viz. continuous moist curing, no moist curing after demolding and air drying after 7-days of initial moist curing. Six different concrete mixes were prepared with ordinary portland cement and a blend of portland cement and combinations of fly ash+silica fume and slag+silica fume The water-to-cementitious materials ratio of all the concrete mixtures was kept constant at 0.45. The properties investigated included workability of the fresh concrete, engineering properties such as cube and modified cube compressive strength, flexural strength, dynamic modulus of elasticity, pulse velocity, shrinkage and swelling, permeability and microstructural properties such as porosity and pore size distribution. The results show that prolonged dry curing results in lower strengths, higher porosity, coarser pore structure and more permeable concretes. It was found that the loss in early age compressive strength due to incorporation of fly ash or slag can be compensated for by the addition of small amounts of silica fume. The engineering and microstructural properties and permeability of concretes containing fly ash or slag appear to be more sensitive to poor curing than the control concrete, with the sensitivity increasing with increasing amounts of fly ash or slag in the mixtures. The incorporation of high volumes of slag in the concrete mixtures refined the pore structure and produced concretes with very low porosity and threshold diameters. The results emphasize that a minimum 7-day wet curing is needed for concrete with mineral admixtures to develop the full potential, and that continued exposure to a drying environment can have adverse effects on the long-term durability of inadequately cured slag or fly ash concretes. The results also confirm that compressive strength alone is not an adequate index to judge the performance of concrete, and the knowledge of the strength, pore structure and permeability are required for this purpose. Slag/silica fume concrete mixtures showed better performance than fly ash/silica fume concrete mixtures as regards the development of engineering and microstructural properties.
2
El-Khatib, Jamal M. "Durability related properties of PFA, slag and silica fume concrete." Thesis, University of Aberdeen, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315418.
Повний текст джерелаАнотація:
Concrete has the largest production of all man-made materials. Compared with other construction materials, it possesses many advantages including low cost, general availability of raw materials, low energy requirement and utilization under different environmental conditions. Therefore, concrete will continue to be the dominant construction material in the foreseeable future. However, durability of concrete and reinfored concrete structures are still of worldwide concern, so producing a good quality concrete which impedes the ingress of harmful substances into it is of paramount importance. Cement replacement materials have been introduced into concrete mixtures for the purpose of improving the durability performance. Hence, the aim of the present investigation is to study the durability of concrete with and without cement replacement materials under various initial curing conditions. In this thesis various concrete mixes with and without cement replacement materials were considered. The cement replacement materials were, pulverised fuel ash, condensed silica fume, and ground granulated blast furnace slag. Superplasticiser was added to the majority of the mixes considered and air entraining agent to some of the mixes. Various curing regimes were employed which comprised hot dry curing to simulate concrete in the hot arid areas in the world and curing at normal temperature. Curing involved air curing, membrane curing and moist curing for fourteen days followed by air curing. A number of tests were conducted at either one particular age or at various ages. These included tests on porosity and pore structure of pastes obtained by mercury intrusion porosimetry technique, water absorption which covers the water absorption of concrete obtained by shallow immersion and the water absorbed by capillary action when the concrete surface is in contact with water, sulphate resistance of concrete which is performed by immersing the concrete specimens in sulphate solution, and monitoring the change in length at various periods of immersion, chloride penetration profiles of concrete at various ages of exposure. In addition to these tests on durability related properties, tests on compressive strength were also performed. Throughout the study a correlation between pore structure and durability related properties is investigated. A comprehensive compilation of chloride penetration data is made and an empirical expression is derived for the prediction of long term diffusion coefficients. At the end of the investigation, limitations of the present study, conclusions and suggestions for future research are made.
3
Shattaf, Nasser Rashid. "Development of high durability concrete for the Arabian Gulf environment." Thesis, University of Sheffield, 1998. http://etheses.whiterose.ac.uk/10213/.
Повний текст джерелаАнотація:
Concrete is probably the most widely used construction material in the world. In the Arabian Gulf region, deterioration of concrete due to the aggressive environment is recognized to be the main factor affecting their structural integrity. The durability of concrete structures can be preserved by various protection methods; however, using cement replacement materials is one of the most effective and economic methods of maintaining their stability as well as extending their service life. The aim of this project is to study four interrelated aspects, namely, (1) the effect of hot environment on the properties of fresh concrete incorporating mineral admixtures, (2), the influence of exposure environment on the engineering properties of hardened concrete, under various curing conditions, without and with mineral admixture, (3), the differences in porosity and pore structure of the same set of mixes, and, (4) the effect of outdoor exposure on the durability-related properties of concrete. To achieve the above aims, the experimental programme involved the study of five different mixes of combinations of silica fume/slag and silica fume. The effects of real exposure to the Arabian Gulf environment of these mixes subjected to four curing regimes, namely, continuous water curing, no water curing after demolding, and air drying after 3 and 7 days of initial water curing were investigated. The properties investigated include (1) consistency and setting times of cement pastes, workability and workability loss with time, (2) engineering properties such as compressive strength, dynamic modulus of elasticity, pulse velocity, shrinkage, expansion and thermal expansion, (3) microstructural properties such as porosity and pore size distribution, (4) durability-related properties such as permeability, water absorption and carbonation depth. The results show that exposure to hot environment results in rapid setting times, faster loss of slump, higher porosity, coarser pore structure and more permeable concretes. It was found that part cement replacement by silica fume and slag improves the quality of concrete mixtures, refined the pore structure and produced concretes with very low porosity and continuous pore diameter in both indoor and outdoor environment. The properties of concrete containing mineral admixture appear to be more sensitive to poor curing than the plain concrete, with the sensitivity increasing with increasing amount of slag in the mixture.
4
Vogt, Carsten. "Ultrafine particles in concrete : Influence of ultrafine particles on concrete properties and application to concrete mix design." Doctoral thesis, KTH, Betongbyggnad, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12161.
Повний текст джерела
5
Mason, Blair Joseph. "The Analysis of Taupo Pumice as an Effective Partial Cement Replacement in Concrete." Thesis, University of Canterbury. Geological Sciences, 2012. http://hdl.handle.net/10092/6825.
Повний текст джерелаАнотація:
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.
6
Brown, Dorothy Kamilah. "Unprocessed rice husk ash as a partial replacement of cement for low-cost concrete." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78143.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 73-76).
Cement is a very valuable commodity as it can be used to construct structurally sound buildings and infrastructure. However, in many developing countries cement is expensive due to the unavailability of local resources to produce enough cement in-country to meet the demand for this material, and therefore it has to be imported. In rice-producing countries rice husk ash-a material naturally high in silica-can be used as a supplementary cementitious material and can substitute a portion of Portland cement in concrete without sacrificing the compressive strength. This study investigates the use of Cambodian rice husk ash in 10, 20 and 30% replacements of Portland cement by mass in mortar, without optimization of the ash by controlled burning. Five ashes collected from different sources in Cambodia were assessed for their suitability for use in rural Cambodian construction via compression strength testing of 2" (50 mm) mortar cubes. A 20% replacement of unprocessed Cambodian rice husk ash was deemed appropriate for use in small-scale, rural structural applications. Low-tech methods of grinding the ash were also investigated and were found to drastically increase the compressive strength of RHA-cement mortars in comparison to mortars made with unground RHA.
by Dorothy Kamilah Brown.
S.M.
7
Taha, Bashar. "The use of mixed colour waste recycled glass as sand/cement replacement in structural concrete." Thesis, University of the West of England, Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429538.
Повний текст джерела
8
Rasool, Sava Tnar, and Omar Sharif. "Expansion of Sickla treatment plant : A study about the replacement of standard concrete to green concrete." Thesis, KTH, Betongbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278542.
Повний текст джерелаАнотація:
Stockholm Vatten has decided to close down the Bromma waste water treatment plantand manage the waste water from Bromma together with the waste water from the formerEolshällsverket to Henriksdal’s waste water treatment plant. Henriksdals wastewater treatment plant will be expanded for higher purification requirements and loads,estimated to be finished until 2040. This entails extensive renovations and additionsto the existing treatment plant in and on Henriksdalsberget, as well as a major expansionof the Sickla plant.The purpose of the study is to investigate an environmentally friendly alternative tothe standard concrete that will be used for the expansion of the Sickla plant. The largestenvironmental villain in concrete is the cement. The aim of this study has beento replace the cement with environmentally friendly additives in the largest possibleamount, thus reducing the negative impact of the cement on the environment.In the present study, a review was made of obtained data with exposure classes, then aliterature study was performed to gain knowledge in the area. With help from experts,two fictitious recipes for each exposure class have been calculated for the standardconcrete and the green concrete. In this way, a careful comparison between the concretetypes was made of the cement’s impact on global warming. Thereafter, a study wascarried out on existing EPDs, which were incorporated into the One Click LCA (2015)software. An LCA in the mentioned software was carried out, which enabled data to becompiled and a comparison of the climate impact between the four different fictitiousrecipes has been done.Compiled and compared data from LCA and analysis of EPDs show that 70% of thestructure with exposure class XD2 gets a 47% reduction in global warming when usinggreen concrete instead of standard concrete. Furthermore, the results show that theremaining 30% of the structure with exposure class XF3/XC4 gets a 20% reductionwhen using green concrete instead of standard concrete. The total reduction in globalwarming when using green concrete instead of standard concrete for the expansion ofSickla treatment plant was calculated to be 40%.Stockholm Vatten har beslutat att lägga ned Bromma reningsverk och leda avloppsvattnetfrån Bromma tillsammans med avloppsvattnet från det forna Eolshällsverkettill Henriksdals reningsverk. Henriksdals reningsverk ska byggas ut för högre reningskravoch belastningar beräknade till år 2040. Detta medför omfattande om- och tillbyggnationeri det befintliga reningsverket i och på Henriksdalsberget samt en storutbyggnad av Sicklaanläggningen.Syftet med detta arbete är att undersöka ett miljövänligare alternativ till standardbetongensom ska användas vid utbyggnaden av Sicklaanläggningen. Då den främsta”miljöboven” i betongen är cementet har målet med denna studie varit att ersätta cementetmed miljövänliga tillsatsmaterial i största möjliga mängd, i syfte att minskacementets negativa inverkan på miljön.I föreliggande arbete har en genomgång utförts på erhållna data med exponeringsklasser,därefter påbörjades en litteraturstudie i syfte att inhämta kunskaper inomområdet. Med hjälp av experter har två fiktiva recept för respektive exponeringsklassräknats fram för standardbetongen och den gröna betongen. Med denna metod genomfördesen noggrann jämförelse mellan de olika recepten avseende cementets inverkanpå den globala uppvärmningen. Därefter undersöktes existerande EPD:er, vilka infogadesin i programvaran One Click LCA (2015). En LCA i den nämnda programvaranutfördes, vilket möjliggjorde att data kunde sammanställas och en jämförelse av klimatpåverkanmellan de fyra olika fiktiva recepten kunde genomföras.Sammanställd och jämförd data från LCA och analys av EPD:er visar att 70% av konstruktionenmed exponeringsklass XD2 får en reducering på 47% på den globala uppvärmningenvid användning av grön betong istället för standardbetong. Vidare visarresultatet att resterande 30% av konstruktionen med exponeringsklass XF3/XC4 fåren reduktion på 20% vid användning av grön betong istället för standardbetong. Dentotala reduktionen på den globala uppvärmningen vid användning av grön betongistället för standardbetong för utbyggnaden av Sickla reningsverk beräknades till 40%.
9
Immelman, Derick Wade. "The influence of percentage replacement on the aggregate and concrete properties from commercially produced coarse recycled concrete aggregate." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80388.
Повний текст джерелаАнотація:
Thesis (MScEng)--Stellenbosch University, 2013.ENGLISH ABSTRACT: The aim of this research is to investigate the potential use of coarse recycled concrete aggregate (RCA) as a material in structural concrete. The lack of knowledge and specifications in South Africa are the main reasons for this research of RCA. By increasing the database of research of RCA in South Africa the possibility of specifications for this alternative building material can be initiated. The implications of such specifications would lead to RCA acceptance in concrete design and therefore reducing the amount of construction and demolition (C&D) waste accumulating at landfill sites and decreasing the extraction of depleting natural aggregates. The objectives that are achieved through this research project are firstly, what is the percentage replacement of RCA to a concrete blend that will produce a material that achieves similar or better results than a concrete blend containing natural aggregates. Secondly, what aggregate properties and limits should be defined in the specification of RCA for it to be accepted as a material in concrete mixtures. The objectives were assessed through examining the geometrical, physical and chemical properties of the aggregate as a material and the fresh and hardened concrete properties of concrete which contains RCA as a constituent. RCA which was processed by a commercial recycling facility which produces concrete masonry units was collected at three different instances. This material was reprocessed in the laboratory to control the grading and amount of fine material not guaranteed by the recycling process. The RCA is then combined with natural aggregate (NA) at the replacement percentages: 0, 15, 30, 50 and 100% which is then used to examine the aggregate properties. It was determined that the physical properties of RCA were dependent on the geometrical properties, while taking into consideration that the geometrical properties are dependent on the source and method of recycling of the original C&D waste. The chemical properties were established as dependent on the physical properties of the RCA. The RCA is then mixed with NA at the same replacement percentages together with other concrete constituents to produce the concrete used to examine fresh and hardened concrete properties. The fresh concrete properties investigated were: slump, slump loss, air content and fresh compacted density. The hardened concrete properties studied were: compressive strength, tensile splitting strength, oxygen permeability, water sorptivity, chloride conductivity, modulus of elasticity, shrinkage and creep. The concrete properties were not significantly influenced by the inclusion of RCA. According to the aggregate and concrete properties examined in this investigation, the full replacement of NA in structural concrete is possible and will improve the sustainable development of the construction industry.
AFRIKAANSE OPSOMMING: Die doel van hierdie navorsing is om ondersoek in te stel na die potensiele gebruik van growwe herwonne betonaggregaat (RCA) as ‘n materiaal in betonstruktuurontwerp. Die gebrek aan kennis en spesifikasies in Suid Afrika is die vernaamste rede vir hierdie navorsing van RCA. Deur die vermeerdering van die databasis van hierdie navorsing van RCA in Suid-Afrika kan die moontlikheid van spesifikasies vir hierdie alternatiewe boumateriaal geïnisieer word. Die implikasie van sodanige spesifikasies sou lei tot RCA aanvaarding in betonontwerp en dus die vermindering van die hoeveelhede konstruksie en sloping (C&D) van afvalversameling by stortterreine en om die ontginning van natuurlike aggregate te verminder. Die doelwitte wat deur hierdie navorsingsprojek bereik word is eerstens, wat is die vervangings persentasie van RCA in 'n betonmengsel wat produseer word wat dieselfde of beter resultate sal lewer as 'n betonmengsel wat uit natuurlike aggregate bestaan. Tweedens, watter aggregaat eienskappe en beperkings moet gedefinieer word in die spesifikasie van RCA sodat dit aanvaarbaar is as ‘n materiaal in betonstruktuur ontwerp. Die doelwitte word geassesseer deur die ondersoek van die geometriese, fisiese en chemiese eienskappe van die aggregaat as ‘n wesenlike materiaal en die vars en verharde betoneienskappe van RCA as ‘n bestanddeel in struktuurbetonontwerp. RCA monsters was geneem by ‘n kommersiele herwinningsfasiliteit wat RCA gebruik om betonsteen eenhede te vervaardig, is op drie verskillende tydperke ingesamel. Hierdie materiaal is herverwerk in die laboratorium om die gradering en die hoeveelheid van fyn materiaal wat nie deur die herwinningsproses beheer is nie. Die RCA was dan gekombineer met NA teen vervangingspersentasies van: 0, 15, 30, 50 en 100 % wat dan gebruik was om die eienskappe van die aggregaat te ondersoek. Daar is vasgestel dat die fisiese eienskappe van die RCA afhanklik van die geometriese eienskappe, met inagneming dat die geometriese eienskappe afhanklik is van die bron en metode van die herwinning van die oorspronklike C&D afval. Dit is gestig dat die chemise eienskappe is afhanklik van die fisiese eienskappe van die RCA. Die RCA is toe gemeng met NA teen dieselfde vervangingspersentasies saam met ander beton bestanddele om beton te produseer wat dan vergelyk kan word met vars en verharde beton eienskappe. Die volgende vars betoneienskappe is ondersoek: insinking, insinking verlies, luginhoud en vars gekompakteerde digtheid. Die volgende verharde betoneienskappe is bestudeer: druksterkte, trek die splintsing van krag, suurstofpermeabiliteit, water sorptiwiteit, chloride geleidingsvermoё, modulus van elastisiteit, krimp en kruip. Die beton eienskappe was nie beduidend beïnvloed deur die insluiting van RCA nie. Volgens die aggregate en beton eienskappe wat in hierdie navorsing ondersoek is, blyk dit dat die volle vervangingswaarde van NA in strukturele beton moontlik is en die volhoubare ontwikkeling van die konstruksiebedryf sal verbeter.
10
Elbusaefi, Adel A. "The effect of steel bar corrosion on the bond strength of concrete manufactured with cement replacement materials." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/68354/.
Повний текст джерелаАнотація:
This thesis presents a study of the bond strength between corroded and uncorroded steel reinforcement and the surrounding concrete within steel reinforced structures. The work is based on concretes manufactured with different types of cement replacement materials, and investigates the influence of the corrosion rate of steel as predicted by concrete permeability. The cement replacement binders included CEM II, blended cements of fly ash (PFA), ground granulated blast-furnace slag (GGBS), metakaolin (MK) and silica fume (SF). The experimental work was conducted by placing 200mm cube test specimens in a saline solution (3.5% NaCl) for different exposure times (3, 7, 10, 14 and 20 days) with an applied external current of 10 mA between the reinforcing steel and a stainless steel counter electrode. Pull-out tests were conducted to evaluate the bond strength between the concrete and the steel reinforcement. The permeability coefficients of concretes were investigated using a relative gas permeability test. The specimens used for determining permeability were cylindrical 100mm diameter and 100mm length, which were oven dried at 105 ºC. The experimental results indicated that the bond strength was governed by concrete properties. Furthermore, the bond strength of the corroded specimens was found to depend on the corrosion levels and varied across all concrete types, depending on the concrete microstructure. Moreover, when the corrosion level exceeded 1.74%, the bond strength began to decline. Thereafter, the bond strength continued to reduce as the corrosion time of the reinforced concrete increased. The relationship between the compressive strength and gas permeability of concretes was inconclusive but the latter does depends on the cement replacement levels. The PFA concretes had the lowest permeability compared to the other two types of concrete (CEM II and GGBS). The permeability of concretes and corrosion rates with different types and levels of cement replacement materials significantly decreased as the age of concretes increased. The improvements in gas permeability and corrosion rate were observed when 40% of cement weight was replaced with PFA. The ABAQUS program was used to model the bond-slip behaviour of different concrete mixes, in addition to a plastic damage model. A cohesive zone element was employed for the steel-concrete interface. During analysis, the numerical model was validated against the results obtained from the experimental tests. The numerical results showed good agreement with the experimental results for CEM II, GGBS and SF concrete specimens, but in the case of PFA concrete where the numerical result of bond strength was overestimated by to the experimental ones.
11
Oliveira, Vanessa Carina Heinrichs Chirico. "Estratégias para a minimização da emissão de CO2 de concretos estruturais." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3146/tde-25072016-144256/.
Повний текст джерелаАнотація:
A maior parte das emissões de CO2 do concreto origina-se na produção do cimento. A estratégia tradicional de minimização da pegada de CO2 tem privilegiado o grau de substituição do clínquer. O trabalho examina o impacto dessa estratégia e também a influência da escolha do fornecedor de cimento sob a ótica de sua matriz energética, a variação do consumo de cimento para concretos de mesma resistência e do desvio padrão do processo produtivo de acordo com o controle do processo de produção do concreto. O método de trabalho inclui dados de revisão bibliográfica, normalização técnica e dados de central de concreto. A estratégia tradicional de escolha do tipo de cimento baseando-se em seu teor de clínquer mostra-se incompleta, pois há uma grande variação e sobreposição dos teores de clínquer permitidos nas normas técnicas brasileiras. No momento atual estima-se que a indústria cimenteira nacional utilize praticamente toda a escória de alto forno gerada no país e a quase totalidade das cinzas de melhor qualidade. Dessa forma, aumentando a demanda de cimento, a produção de clínquer aumenta, e o teor de adições no clínquer diminui dentro das extensas faixas permitidas pelas normas técnicas. Nesse cenário, a seleção de um tipo de cimento em detrimento de outro pode reduzir o impacto de uma obra específica, embora não traga necessariamente benefícios ambientais para o país. A troca da matriz energética por carvão vegetal de madeira de florestas plantadas pode minimizar a parcela de emissões provenientes de combustíveis do cimento, diminuindo a emissão de 350 kg para 10 kg de CO2 por tonelada de clínquer produzida. A eficiência do processo de formulação do concreto apresenta grande potencial para diminuir a quantidade de cimento utilizada no concreto, diminuindo, assim, as emissões totais de CO2 do concreto. Os dados levantados apontam uma variação de consumo de cimento de mais de 100% para concretos de mesma resistência. A influência do desvio padrão das condições de produção apresenta potencial menor para a diminuição das emissões, diminuindo no máximo 13% o consumo de cimento no concreto. A combinação das quatro estratégias estudadas demonstra a complexidade da emissão do concreto e o grande potencial para mitigar suas emissões de CO2. A necessidade de informações específicas sobre a emissão dos cimentos, seu teor de clínquer e sua matriz energética, uma técnica de dosagem otimizada e um controle das condições de produção do concreto demonstram que há, tanto para fornecedores de matérias primas do concreto quanto para os usuários e produtores do concreto, muito a ser feito para minimizar as emissões deste material tão consumido.Most of concretes CO2 emissions originate from cement production. The traditional strategy for minimizing the CO2 footprint of concrete has favored the degree of clinker replacement. This paper examines the impact of this strategy and also the influence of the choice of the cement supplier based on the fuel composition in cement production, the variation of cement usage in concretes of the same strength and the standard deviation of the production process of concrete based on the control of its production process. The method of work uses data from literature, technical standards and data from a concrete central. The traditional strategy of the choice of cement type based on its clinker content is insufficient due to the extensive and overlapping clinker content range of different cement types allowed in Brazilian technical standards. At the present time, it is estimated that the cement industry utilizes all of the blast furnace slag generated in the country and nearly all quality fly ash. Consequently, if there is an increase in the demand for cement, there is an increase in clinker production, and the rate of additions to the clinker decreases, respecting the extensive limits permitted by technical standards. In this scenario, the selection of blast furnace slag cement and fly ash cement does not necessarily offer environmental benefits to the country as a whole and does not demonstrate a global impact, despite the possibility of benefiting specific construction sites. The substitution of the fuel mix for coal from planted forest wood can lower the portion of cement emissions due to fuel burning from 350 kg to 10 kg of CO2 per tonne of clinker produced. The efficiency of the concrete mix formulation shows great potential to lower the amount of cement usage in concrete, thus lowering the total CO2 emissions of concrete. The data presented point to a variation of more than 100% of cement content in concretes of the same strength. The influence of the standard deviation of the production process shows smaller impact on lowering concrete CO2 emissions shows that there is a maximum potential of 13% of lowering cement content in concrete. The combination of the four strategies studied demonstrates the complexity of concretes emissions and the great potential for mitigating its CO2 emissions. The need for information on cements specific emissions, its clinker content and fuel mix, the concrete mix formulation and the variability of the production process of concrete show that there is, for concrete raw material suppliers as well as concrete producers and users, a lot to be done to minimize the emissions of this widely consumed material.
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Muller, Scott D. "The femoral cement mantle in total hip arthroplasty." Thesis, University of Newcastle Upon Tyne, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273507.
Повний текст джерела
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Ouchagour, Youssef. "Suitability of recycled concrete aggregate for use in binary cement concrete." Thesis, Kingston University, 2007. http://eprints.kingston.ac.uk/20327/.
Повний текст джерелаАнотація:
The principles of sustainable construction require the prudent use of natural resources and the maximum recycling and reuse of waste. In keeping with this approach, much research was undertaken to increase the use of recycled aggregates derived from construction and demolition wastes as an alternative to primary aggregates in construction. It is now increasingly recognised that the use of coarse recycled concrete aggregate (RCA) in concrete construction represents a further potential outlet for the material. Several investigations have been made to study the effects of coarse RCA on the fresh and hardened properties of Portland Cement (PC) concrete. While these studies suggest the potential use of RCA in a range of concrete applications, issues relating to its suitability in binary cement concrete mixes, relevant to practice, have not been addressed. Against this background, the present study was undertaken to examine the suitability of using coarse RCA in BS 8500 designated concrete mixes produced using binary cements. The binary cements selected were (i) PC/PFA cement, a blend of 70% PC/ and 30% Pulverised Fuel Ash by mass and (ii) PC/SF cement, a blend of 90% PC and 10% Silica Fume by mass. The binary cements were blended in the mixer during concrete production. The effects on the fresh, engineering and durability properties of concrete, of replacing coarse natural aggregates (NA) by coarse RCA by up to 100% in concrete have been established. The RCA mixes were designed to achieve equal 28 day cube strengths as their corresponding NA mixes. The aggregate characterisation results showed that concrete debris obtained from construction and demolition waste can be used to produce clean and properly graded RCA suitable for use in concrete production in accordance with the EN 12620 requirements. The results of the fresh properties of concrete showed that although the slump measurements remained within the allowable tolerances, the use of high RCA contents affected the workability and stability of the mixes. Studies of the hardened concrete properties, comprising the bulk engineering (Compressive cube and cylinder strength, flexural strength, modulus of elasticity, drying shrinkage and swelling deformations) and durability properties (near surface absorption, carbonation, chloride ingress, sulphate attack) showed that RCA concrete mixes made with binary cements had, a comparable or better performance when compared to their corresponding concrete mixes made with PC only. Practical implications derived from the findings of the study are also outlined for the use of RCA in binary cement concrete construction. Overall, the study has shown that RCA is suitable for the production of a wide range of designated mixes made with binary cements with a satisfactory engineering and durability performance, provided that the mixes are designed for equivalent 28 days cube strength.
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Elgalhud, Abdurrahman Ahmed T. A. "Durability potential of Portland limestone cement concrete." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7903/.
Повний текст джерелаАнотація:
There is an increasing global concern that has led to efforts to lessen the carbon footprint of the cement industry and make concrete manufacturing more sustainable by using other types of materials as supplements or alternatives, primarily for Portland cement (PC). This research work is concerned with the analytical systemisation, including the analysis, evaluation and structuring of global published experimental results, of ground limestone (GLS) used in concrete as a partial replacement of PC. The work is focussed on the physical and chemical characterisation of GLS and its effects on pore structure (in terms of porosity, water absorption and sorptivity), compressive strength and the durability of the concrete in terms of the carbonation and chloride ingress and the corrosion of steel reinforcement, including a statistical modelling of the carbonation of concrete with Portland limestone cement (PLC). Overall, it is suggested that, though the use of GLS up to 25% with PC should not impair the pore structure, the limit on GLS content for its effect on strength is likely to be about 15%. This should be considered where a higher proportion of GLS content is allowed in the standards. It is also shown that the carbonation rate and chloride ingress into concrete increase with increasing GLS content.
15
Mostafa, Raqibul. "Wideband electromagnetic characterization of Portland cement concrete." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-06112009-063132/.
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Gouru, Harinath. "Laboratory evaluation of asphalt-portland cement concrete composite." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-12232009-020518/.
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Gul, Waqar Ahmed Waqar. "Effect Of Recycled Cement Concrete Content On Rutting Behavior Of Asphalt Concrete." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609765/index.pdf.
Повний текст джерелаАнотація:
Disposed waste materials remained from demolished buildings have been an
environmental problem especially for developing countries. Recycled Cement
Concrete (RCC) is one of the abundant components of waste materials that
include quality aggregates. Use of RCC in asphalt concrete pavements is
economically a feasible option as it not only helps in recycling waste materials but
also preserves natural resources by fulfilling the demand for quality aggregate in
pavement constructions. However, due to variability in RCC characteristics, a
detailed evaluation of its effect on asphalt concrete performance is required.
In this study, effect of RCC content on rutting potential of asphalt concrete is
investigated using laboratory prepared specimens. Rutting susceptibility of the
specimens is determined using repeated creep tests performed in the uniaxial
stress mode. Because of the aspect ratio requirements for the repeated creep test,
the standard Marshall mix design procedures were modified based on the energy
concept by changing the compactor device and the applied design number of
blows. The modified specimens were tested to determine a number of parameters
that can describe the rutting behavior of the tested mixes. The findings indicate
that slope constant and flow number give relatively stronger relationships with
rutting behavior as compared to the other rutting parameters. While increasing the RCC content yields improved rutting performance for coarse graded specimens, it
dramatically reduces the performance for fine graded specimens.
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Khorami, M. "Application of natural and synthetic fibres as a replacement for asbestos fibres in cement boards." Thesis, Coventry University, 2011. http://curve.coventry.ac.uk/open/items/33ff6ca1-107b-482b-b598-f7ab050d8d42/1.
Повний текст джерелаАнотація:
The use of asbestos fibres in construction products has been banned in European countries for about two decades due to its effect on human health. At present, many developing countries use asbestos cement board as one of the most important construction products for roofing, cladding and partition walls. The Hatschek process is the most commonly used method to produce asbestos Fibre Cement Board (FCB). There are two major problems for the asbestos FCB manufacturers in replacing their products with non-asbestos FCB. The first one is finding materials and fibres that are available and competitive in price compared to asbestos fibres, and the second is providing inexpensive machines and equipment to produce non-asbestos FCB. In this research, an effort has been made to solve these two major problems. After the initial laboratory investigations on several natural and synthetic fibres some of the fibres with potential use in FCB were chosen for the further investigations. A slurry vacuum dewatering process was then designed and made for the laboratory use. The performance of material selections and mix designs selected from the laboratory studies were subsequently verified with factory Hatschek process in a factory site trial. Many specimens with natural and synthetic fibres incorporating silica fume and limestone powder were made and tested in the laboratory. Silica fume and limestone powder were used for enhancing flexural strength and suppression of alkalinity to reduce breakdown of the cellulose fibres. The results of mechanical, physical and II durability tests were analysed. The microstructure of the fibres and composites was also studied by SEM (Scanning Electron Microscopy). At some stages, mix design optimization was carried out to gain the highest flexural strength. The most suitable mixes were chosen for the factory site trials. A number of full-scale non-asbestos trial boards were made successfully in an asbestos FCB factory and tested in accordance with the current national and international standards. The results indicated that the trial boards fulfilled the requirements of the relevant standards. Based on the outcome of this research, a combination of acrylic fibres and waste cardboard in a mix incorporating silica fume and limestone powder in addition to Portland cement can be used to replace asbestos fibres. Although broadly compatible with the asbestos cement production process, this formulation change will necessitate some changes to the existing production lines in asbestos cement factories to produce non-asbestos FCB.
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Dimov, Dimitar. "Fundamental physical properties of graphene reinforced concrete." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/34648.
Повний текст джерелаАнотація:
The global warming has increased with unprecedented levels during the last couple of decades and the trend is uprising. The construction industry is responsible for nearly 10% of all carbon emissions, mainly due to the increasing global population and the large demand for housing and civil infrastructure. Concrete, which is the most used construction material worldwide, is found in every type of building as it provides long term structural stability, support and its main constituent cement, is very cheap. Consequently, due to the raising concerns of high average temperatures, the research community started investigating new, innovative methods for substituting cement with 'greener' materials whilst at the same time improving the intrinsic properties of concrete. However, the manufacturing complications and logistics of these materials make them unfavourable for industrial applications. A novel and truly revolutionary method of enhancing the performance of concrete, thus allowing for decreased consumption of raw materials, lies in nanoengineering the cement crystals responsible for the development of all mechanical properties of concrete. Graphene, a two-dimensional sheet of carbon atoms arranged in a hexagonal lattice, is the most promising nanomaterial for composites' reinforcement to this date, due to it's exceptional strength, ability to retain original shape after strain, water impermeability properties and non-hazardous large scale manufacturing techniques. I chose to investigate the addition of liquid-phase exfoliated graphene suspensions for concrete reinforcement, aiming to improve the fundamental mechanical properties of the construction material and therefore allowing the industry to design buildings using less volume of base materials. First, the method of liquid exfoliation of graphene was developed and the resulting water suspensions were fully characterised by Raman spectroscopy. Then, concrete samples were prepared according to British standards for construction and tested for various properties such as compressive and flexural strength, cyclic loading, water impermeability and heat transport. A separate, in-depth, study was carried out to understand the formation and propagation of micro-structural cracks between the concrete's internal matrix planes, and graphene's impact on total fracture capacity and resistance of concrete. Lastly, multiple experiments were performed to investigate the microcrystallinity of cement hydration products using X-Ray diffraction. In general, all experimental results show a consistent improvement in concrete's performance when enhanced with graphene on the nanoscale level. The nanomaterial improves the mechanical interlocking of cement crystal, thus strengthening the internal bonds of the composite matrix. This cheap and highly scalable method for producing and mixing graphene with concrete turns it into the first truly applicable method for industrial applications, with a real potential to have positive impact on the global warming by decreasing the production of concrete.
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Griffin, Isobel Margaret. "Deterioration mechanisms of historic cement renders and concrete." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8104.
Повний текст джерелаАнотація:
Since the introduction of Portland cement in the early nineteenth century the number of buildings constructed from concrete or using cement mortars and renders has grown exponentially, and cement is one of the most common building materials in use today. Consequently a significant proportion of the built heritage contains cementitious materials. The relative youth of these buildings means that less research has been undertaken to understand how and why they deteriorate than for traditional buildings, and that the development of appropriate conservation methods and techniques is less advanced. The primary aim of this research was to understand the causes and mechanisms of some of the types of deterioration commonly found in historic concrete and cement buildings and structures, with reference to the Second World War reinforced concrete and cement-rendered buildings at East Fortune airfield in East Lothian, Scotland. Additional aims were to investigate the efficacy of the building repairs and maintenance regimes undertaken to date, and to make recommendations for the future conservation of the buildings. East Fortune airfield contains a number of cement-rendered brick masonry buildings and a reinforced concrete air raid shelter. The initial visual survey identified several types of deterioration, from which the blistering and flaking of the render; the cracking and delamination of the render; and the spalling of the concrete in the air raid shelter were selected for further research. The research included time lapse photography, non-destructive testing, environmental monitoring and the physical, chemical and petrographic characterisation of the building materials. Hypotheses regarding the causes of deterioration were tested in the laboratory, for example with linear variable displacement transducer measurements, and modelled using crack propagation theories and models for water transport through porous media. It is demonstrated that the blistering and flaking of the render is caused by shale aggregate particles, which undergo sufficient expansion during freeze-thaw cycles to crack the surrounding render. This phenomenon is termed ‘pop-outs’ in the concrete literature. The more catastrophic cracking and delamination of the renders is also due to freeze-thaw cycling, which is shown to cause significant damage provided the moisture content of the render is above a certain threshold level. This type of deterioration has occurred at an accelerated rate for some of the modern render repairs, due to an inadequate understanding of the properties of the original and repair materials. In particular, the properties of the bricks are critical to the performance of the cement renders, and it is found that the sorptivity of historic bricks may vary considerably depending upon the orientation of the brick. Finally, the diagnosis for the air raid shelter is that the corrosion of the steel reinforcements is caused by high levels of chlorides present within the raw materials used to make the pre-cast concrete sections. The results of the investigations are used to suggest building conservation solutions for this particular site. Furthermore, since the deterioration mechanisms investigated are common for historic cement and concrete, the findings are relevant to many other sites. The over-arching methodology used to investigate the deterioration at the site and the methodologies developed to test particular hypotheses are also applicable for other investigations of historic building materials. There is much about this research that is innovative and new. The work on render cracking compares the results of dilation tests on cementitious and ceramic materials, which has not been done previously, and the pop-outs diagnosed in the work on render flaking have rarely, if ever, been reported for cement renders. The modelling work undertaken to quantify the stresses produced by the pop-outs and to explain the inclined crack formation patterns is entirely original. The use of petrography to diagnose causes of render failure is described in the literature, but this is one of very few case studies to be written up, and the work on the air raid shelter constitutes the only formal investigation of this type of Stanton shelter.
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Marciano, Junior Everaldo. "Sustainable development and the cement and concrete industries." Thèse, Université de Sherbrooke, 2003. http://savoirs.usherbrooke.ca/handle/11143/1754.
Повний текст джерелаАнотація:
Sustainable development is an attempt to mitigate the environmental damages of the past, to adjust the present exacerbated superfluous pattern of consumption and the increasing social gaps between nations, in order to provide the future generations a fairer society living in a more healthy environment. Up to now climate changes has been the focus of the discussion, but sustainable development is a much more broader issue. Just 20% of the world population has a high standard of living and consumes the greatest part of energy and raw materials and as a consequence generates the majority of CO 2 emissions, the main greenhouse responsible for climate change. At the same time, 50% of the population earns less than $2 US a day gasping for sanitation, hospitals, schools, houses just to satisfy the minimum of dignity. In such a scenario the cement and concrete industries can play a key role either for solving social problems as for helping to mitigate the environment burden. Cement industry is often focused as a polluting industry, responsible for 6% of world CO2 emissions, and concrete is frequently presented as a low technological added value product that generates around 1 billion tonnes of wastes per year. This is a common unfair perception that reveals a lack of information and adequate analysis. The cement industry experienced an extraordinary reduction in gas and dust emissions as well as energy saving rooted in significant technological investments in the seventies and eighties. Its CO2 emission is much lower than that of other industrial segments, such as transportation and progresses continue. At the same time millions of tonnes of industrial by-products and wastes generated by other industrial sectors are consumed and valorized by the cement and concrete industries every year. As a construction material, concrete fulfils almost all the social and technological needs of societies. The spectrum of available concrete ranges from some MPa to 800 MPa, exhibiting high flowable properties or low noise when casting, showing good thermal performance at low cost, evidencing the immense technological progresses achieved in recent years. With the current available technology a much longer life cycle of concrete structures should be achieved. An infrastructure lasting longer will contribute to reduce waste generation and alleviate budgets to invest in other social requirements instead of"indefinitely paying" for rebuilding or repairing structures in benefit primarily of contractors."--Résumé abrégé par UMI.
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Dachtar, John. "Calcium sulfoaluminate cement as binder for structural concrete." Thesis, University of Sheffield, 2004. http://etheses.whiterose.ac.uk/10270/.
Повний текст джерелаАнотація:
The use of calcium sulfoaluminate (CSA) cement as a concrete material can save energy by 25% .and reduce CO2 emissions by 40%. The potential of using ggbs, pfa, bottom ash, pyrite ash and other by-product and waste materials to produce the CSA cement can result in further environmental benefits. The research undertaken in this investigation aimed to explore the potential of CSA cement as the main binding material for structural grade concrete, identify the limitation of this material in this context and suggest possible applications for the resulting concrete. The experimental study covered a number of variables, anhydrite content, OPC and lime Inclusion, water/cement ratio and curing regimes. The investigation encompassed the preparation of CSA cement in the laboratory and the use of a commercially produced CSA. The systems investigated included paste specimens prepared with laboratory produced CSA and commercially manufactured CSA and concrete specimens prepared with the commercially manufactured CSA cement. The investigation in paste included hydration product identification using X-ray diffractometry and scanning electron microscopy, expansion and compressive strength development. Setting time of CSA cement paste was determined using samples made with the commercially manufactured CSA cement. The properties of fresh and hardened concrete investigated were setting time, workability using both slump test and Tattersall's two-point test, expansion, compressive strength, indirect tensile strength, flexural strength, oxygen permeability, water absorption and rapid chloride permeability. The research carried out in this investigation on CSA cement paste established that ettringite was the main product of hydration. The hydration reaction occurred at a fast rate, with hydration being almost complete within a week after casting. Formation of ettringite as a result of CSA and anhydrite hydration did not cause expansion but in the presence of calcium hydroxide in the system, resulted in expansion. In systems where expansion was evident after long-term water storage, it is suggested that this had resulted from the ettringite imbibing water and expanding. This expansion was found to be controlled by the presence of internal constraints, such as unhydrous particles or aggregates (in the case of concrete). The use of low water/cement ratio and the resulting low water absorption can further reduce such expansion. Concrete workability was improved in CSA cement and anhydrite systems over that of control OPC concrete resulting in lower water demand. The use of OPC as cement replacement in CSA concrete adversely affected the workability and accelerated the initial setting time. The compressive and flexural strength of concrete made with CSA cement and anhydrite were considerably superior to those of control OPC concrete but, in general, were comparable with respect to their indirect tensile strengths. However, compressive strength was found to degrade by 10-20% with prolonged water storage and the OPC, as cement replacement, did not contribute significantly to strength. The need for water for CSA cement hydration was generally higher than the mixing water required for workability. As a consequence, CSA concrete is expected to have lower capillary porosity than OPC concrete. This fact was manifested in the lower water absorption value found for CSA concrete. High oxygen permeability found for CSA and the inconclusive results of the rapid chloride permeability test suggest that further research into the durability performance and durability related properties is required. The high early-age flexural strength of CSA concrete is an advantage in rigid pavements and pre-stressed concrete. The low pH of CSA concrete is another advantaged when glass or vegetal fibres are used. The concrete, however, needs to be of low permeability to safeguard against steel corrosion.
23
Sergi, George. "Corrosion of steel in concrete : cement matrix variables." Thesis, Aston University, 1986. http://publications.aston.ac.uk/14236/.
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Feng, Qiu Ling. "Chemical and microstructural investigations on slag hydration products." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 1989. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=59672.
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25
Harper, Elizabeth Jane. "Development and characterisation of a hydroxyxapatite reinforced poly(ethylmethacrylate) bone cement." Thesis, Queen Mary, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339214.
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Cheung, Yin Nee. "Investigation of concrete components with a pseudo-ductile layer /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20CHEUNGY.
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Baker, Nina Crampton. "High alumina cement in the marine environment." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316529.
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Wenglas, Lara Gilberto. "Quality evaluation of Portland cement concrete at early age with free-free resonant column." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Trussoni, Matthew. "Fracture Properties of Concrete Containing Expanded Polystyrene Aggregate Replacement." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/285.
Повний текст джерелаАнотація:
Fracture mechanics is applied to study the behavior of concrete containing expanded polystyrene (EPS) aggregate replacement. The EPS replaces a portion of the normal weight fine aggregate. Previous research has shown EPS aggregate replacement changes the failure mode in compression from a typical instantaneous failure, as in normal weight concrete (NWC), to a more gradual dissipation of load carrying capacity. This behavior is investigated through the use of fracture mechanics. The fracture energy, critical stress intensity factor and characteristic length of EPS concrete, NWC and fiber reinforced concrete (FRC) are experimentally determined. The two types of tests used to study these properties are the three point bending test recommended by the RILEM technical committee and a wedge splitting test developed recently. The conclusions derived from this research demonstrate that EPS aggregate replacement increases the size of the fracture process zone in front of the crack tip. This increase in size changes the failure mode of concrete allowing it to maintain load after reaching peak load and absorb more energy during the fracture process.
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Alshehri, Saad. "Binding of Nitrite in Concrete, Cement Mortar and Paste." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5899.
Повний текст джерелаАнотація:
Calcium nitrite as a corrosion inhibitor is mainly used to protect steel reinforcement in concrete by reducing its corrosion rate. Hence the effectiveness of calcium nitrite depends on its availability as a free nitrite in the pore solution. The present research work aims to determine the concrete mixture component mostly responsible for nitrite binding in concrete. Firstly, the experimental program included testing of nitrite binding in cement paste. Secondly, the effect of adding the fine aggregate (mortar mix) on nitrite binding was assessed. Finally, the mix with coarse aggregate (concrete mix) was evaluated. In-situ leaching method was used to obtain the pore solution that was needed.
Measurement of pore solution with the In-situ leaching method and after an average of 48 days showed that concrete specimens have the most nitrite binding capacity. Then, the binding of nitrite was less in mortar and paste specimens respectively. Therefore, concrete specimens bind more nitrite compared to the paste and mortar specimens. The binding ratio increased whenever the nitrite addition level increased. Nevertheless, the free nitrite were similar in the case of the lowest nitrite addition for all types of mix. The pH levels for the mixes with nitrite present, were lower than those of the control mixes.
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Khoury, Issam S. "Impact of Base Stiffness on Portland Cement Concrete Pavement." Ohio University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1448963853.
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Du, Plessis Hanli. "The use of gasification ash in cement and concrete." Diss., University of Pretoria, 2006. http://hdl.handle.net/2263/23908.
Повний текст джерелаАнотація:
Cement is an essential material in today’s society because, as a major constituent of concrete, it forms a fundamental element of any housing or infrastructure development. The chemical process of making cement clinker produces CO2, a major greenhouse gas contributing to climate change. This makes it imperative for us to find ways of using this resource more efficiently. Using waste from other industries, as a raw material is a huge opportunity for the cement industry to reduce its environmental impact. Cement extenders are used as a substitute for some of the Portland cement in concrete. The reasons for the use of extenders, is a growing awareness of the engineering, economical and ecological benefits and the variety of useful enhancements, which they give to the concrete properties. The aim of the research is to determine whether a gasification ash can be used as a cement extender in concrete. In this study the properties of cement and concrete containing gasification ash was compared to the properties of cement and concrete containing fly ash. The physical, chemical and mineralogical composition of a gasification ash sample was investigated, and it was found that gasification ash has an angular shape and a similar chemical composition as fly ash. The chemical requirements of the gasification ash meet the majority of the requirements specified for cement extenders. Where limits are exceeded it is by a very narrow margin. The effect of a gasification ash on the short and long term properties of concrete of both interblending and intergrinding was investigated. The experimental work revealed that gasification ash improves the compressive and tensile strength of concrete in both interblending and intergrinding. Gasification ash does not have a detrimental effect on stiffness of concrete, and did not creep significantly more than concrete containing fly ash. The porosity and permeability does not increase when gasification ash is used as a cement extender. Gasification ash should therefore not decrease the durability of concrete. The use of gasification ash as a cement extender has advantages to both the cement industry and the environment.Dissertation (MEng(Structural))--University of Pretoria, 2007.
Civil Engineering
unrestricted
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Wilde, William James. "Life cycle cost analysis of Portland cement concrete pavements /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Fernandez, Lopez Rodrigo. "Calcined clayey soils as a potential replacement for cement in developing countries /." Lausanne : EPFL, 2009. http://library.epfl.ch/theses/?nr=4302.
Повний текст джерелаАнотація:
Thèse Ecole polytechnique fédérale de Lausanne EPFL, no 4302 (2009), Faculté des sciences et techniques de l'ingénieur STI, Programme doctoral Sciences et Génie des matériaux, Institut des matériaux IMX (Laboratoire des matériaux de construction LMC). Dir.: Karen Scrivener.
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Mburu, Gathuru. "Cement keyhole fixation of the acetabular component of a total hip replacement." Thesis, University of Aberdeen, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342193.
Повний текст джерелаАнотація:
Loosening of the cemented acetabular component of a total hip replacement is 2-3 times more common than femora stem failure. Cement keyholes drilled into the acetabulum have been recommended to improve this fixation but little is known of the optimum sizes and locations of these holes. This study investigated the diameter, depth and number of keyholes to be drilled to maximise the failure torque in a model system. A two-pronged approach was used; mechanical testing and finite element (FE) analysis. A Taguchi experimental design was used to identify the most significant factors and to predict the best configuration of keyholes within the constraints of the acetabular dimensions. One hole at each of the pubic, iliac and ischial sites, of 12 mm diameter and 6 mm depth, was found to be the optimum configuration. The failure torque was most strongly dependent on the hole diameter in the pubic region, decreased with increasing hole depth and was not sensitive to the number of holes. Both two dimensional and three dimensional FE analyses of a single cement keyhole showed that the lowest von Mises stress and the best distribution of shear stress was for the hole of 12 mm diameter and 6 mm depth. The results of the two approaches used here are in excellent agreement. The final stage of this study investigated the optimisation of the keyhole shape and the design of a suitable drill bit for surgical use.
36
O'Farrell, Martin. "The durability of mortar with ground clay brick as partial cement replacement." Thesis, University of South Wales, 1999. https://pure.southwales.ac.uk/en/studentthesis/the-durability-of-mortar-with-ground-clay-brick-as-partial-cement-replacement(31d9c04b-b950-4be8-be40-46984c1c30d6).html.
Повний текст джерелаАнотація:
The work in this thesis examines the suitability of utilising ground waste brick as a cement replacement material. The brick types investigated were obtained from the UK,Denmark, Lithuania and Poland. Cement was partially replaced by various quantities and types of ground brick in mortar and concrete. Compressive strength, pore size distribution and sorptivity of mortar generally all benefit from the presence of ground brick and the greatest effect can be seen after water curing for one year. Compressive strength of concrete is also shown to increase as the fineness of ground brick increases although the optimum particle size for ground brick in concrete is still to be determined. The ground bricks investigated have a significant effect on the performance of ground brick mortar when exposed to sodium sulphate solution and synthetic seawater. It is seen that depending on the chemical and phase composition, the effect of ground brick can increase substantially the rate of deterioration of mortar or can reduce significantly the expansion observed. No definite mechanism was identified as being responsible for the observed deterioration of mortar exposed to sodium sulphate solution although it seems likely that water intake due to ettringite formation and adsorption of water by the resultant colloidal product are the primary causes of expansion. Sulphate content, glass content and oxide chemistry of brick are key factors as to its performance when used as a cement replacement material in mortar. Bricks with a high proportion of low calcium glass make very effective pozzolans. Bricks with high calcium glass or a low proportion of glass should not be used as pozzolans. Small amounts of sulphate in ground brick do not have any serious deleterious effects on ground brick mortars and can be beneficial. It is established that it is technically feasible to partially replace cement with ground brick in mortar and concrete, depending on its chemical and phase composition to produce a more durable, cost effective and (due to the lower cement content) a less environmentally damaging material than that produced without cement replacement.
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Nath, Pradip. "Durability of conrete using fly ash as a partial replacement of cement." Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/1593.
Повний текст джерелаАнотація:
Utilization of fly ash as a supplementary cementitious material adds sustainability to concrete by reducing the green house gas emission associated with cement production. Fly ash is a by-product of coal fired power stations. The properties of fly ash depend on the type of coal and its burning process. Due to the variation in composition, different fly ash affects the properties of concrete differently. Research data on the performance of concrete containing the Western Australian fly ash is scarce in literature. In this study, mechanical and durability properties of high strength concrete using Class F fly ash from Western Australia were investigated. The ACI 211.4R-08 guidelines were followed to design two series of concretes, each having one control concrete and two fly ash concretes using 30% and 40% fly ash as cement replacement. Fly ash concretes of series A were designed by adjusting the water to binder (w/b) ratio and total binder content to achieve the same strength grade of control concrete. In series B, w/b ratio and total binder content were kept constant in all the three mixtures. Samples were water cured for 7 and 28 days; and were tested at different ages. The mechanical properties were tested by compressive strength, tensile strength and flexural strength test. The investigated durability properties were drying shrinkage, volume of permeable voids, water and air permeability, carbonation and chloride ion penetrability.The 28-day compressive strength of the concrete mixtures varied from 65 to 85 MPa. The fly ash concretes showed lower drying shrinkage than control concrete when designed with adjusted w/b ratio and the total binder content. Inclusion of fly ash reduced sorptivity and water permeability significantly at 28 days. Fly ash showed no adverse affect on air permeability of concrete. Fly ash concretes showed similar carbonation and had less chloride ion penetration as compared to the similar grade control concrete. In general, incorporation of fly ash as partial replacement of cement improved the durability properties of concrete at early age when w/b ratio was adjusted to achieve similar 28-day strength of the control concrete. The durability properties improved with the increase of fly ash content from 30% to 40% of the binder and with the increase of age. Fly ash concretes of series A achieved similar service life of control concrete in carbonation and resulted in higher service life than that of the control concrete, when chloride diffusion was considered as the dominant form of attack.
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Mousavi, Marjan. "Life Cycle Assessment of Portland Cement and Concrete Bridge : Concrete Bridge vs. Wooden Bridge." Thesis, KTH, Industriell ekologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122462.
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Today global warming mitigation, natural resource conservation and energy saving are some of the significant concerns of different industries, such as cement and concrete industries. For that reason, a streamlined life cycle assessment (LCA) model of one ton of a Portland cement, CEM I produced in Cementa AB’s Degerhamn plant, has been developed by using the LCA software KCL-ECO. LCA is a tool that identifies in which stages of a product’s life cycle the most environmental burdens occur. The environmental analysis was limited to identify total energy consumption and total carbon dioxide (CO2) emissions per ton of Portland cement. Results show that the most significant energy consumption and CO2 emissions are related to clinker kiln, due to the process of calcination of limestone and fuel combustion in the kiln. Of total CO2 emissions, 52 % and 46 % result from the calcination process and fuel combustion respectively. One of the applications of CEM I is in construction of concrete bridges. Therefore an LCA model of a concrete bridge located north of Stockholm was developed in KCL-ECO. Environmental indicators calculated are: total CO2 emissions and energy consumption through the entire life cycle of the bridge. CO2 uptake or carbonation of the concrete during the service life of the product and end of life treatment is one of the advantages of concrete products. During the carbonation process, some of the total CO2 released from calcination will be absorbed into the concrete. Results indicate that production of raw materials and transports during the life cycle of the concrete bridge, are main contributors to total CO2 emissions. Among raw materials, cement production has the highest CO2 emissions. Energy consumption is mainly related to concrete and concrete products production. CO2 uptake during the use phase of the bridge is small compared to total CO2 emissions from calcination. Furthermore, the results show that different waste handling practises result in different CO2 uptake behaviours. The total CO2 uptake from crushing and storing of the demolished concrete (scenario 1) and landfilling of the demolished concrete (scenario 2) is 10 % and 5 % of the total CO2 emissions from calcination respectively. Since comparison of different construction materials from an environmental point of view is always desirable, the LCA tool was used to compare the total energy consumption and the CO2 emissions from a concrete bridge and a wooden bridge. The functional unit was defined as 1 square meter of bridge surface area, since the bridges were of different sizes and shapes. In this comparison the total emissions and energy consumption were much higher for the concrete bridge than for the wooden bridge. In order to show how different assumptions could affect the results, a virtual concrete bridge with the same shape and size as the wooden bridge was designed and compared with the wooden bridge. The functional unit selected for this case was one bridge. In this case the virtual concrete bridge requires less energy, while the wooden bridge emits less CO2 to the atmosphere. For the wooden bridge, CO2 in growing forests was included, which could be debated. Overall, a comparison of the environmental performance of the wooden bridge and the concrete bridges was more complex than initially expected and great care is recommended in choosing material and application. With concrete, the design (and quantity of material used) seems to be a very sensitive parameter and may result in much larger energy used and CO2 emissions than a wooden bridge. On the other hand, the virtual bridge comparison showed that concrete advantages such as higher durability and lower maintenance may be theoretically combined with a comparable energy and climate performance as a wooden alternative.
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Hailey, Jacquolyn Lesley. "The influence of storage environment on the fracture behaviour of acrylic bone cement." Thesis, University of Bath, 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336074.
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Matenda, Amanda Zaina. "GEOPOLYMER CONCRETE PRODUCTION USING COAL ASH." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1654.
Повний текст джерелаАнотація:
Coal powered power plants account for more than 40 percent of the electricity production of the United States. The combustion of coal results in a large number of solid waste materials, or coal combustion byproducts (CCBs). These waste materials are stored in landfill or ponds. The construction industry is heavily reliant on concrete which is used to make the building blocks for any type of structures, bricks. Concrete is a composite material made of a binder and coarse and fine aggregate. The most widely used binder in concrete production is Ordinary Portland Cement (OPC). Since cement manufacture is costly and environmentally damaging, research has increased in recent years to find a more readily available binder. This study aims at investigating the properties of Illinois fly ash as a binder in the production of geopolymer concrete. Geopolymer concrete is an innovative material made by using Alumina and Silica rich materials of geological origins as a binder as well as an alkali activated solution. Sodium Silicate and Sodium Hydroxide were used to make the activator solution of two different ratios. Geopolymer Concrete with a ratio of 1:1 of Sodium Silicate to Sodium Hydroxide reached a compressive strength above 6000 psi while samples made with a ratio of 1:2 reached a compressive strength above 4000 psi. This environmentally-friendly, green concrete was also found to have a cost comparable to conventional concrete.
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Peng, Joe Zhou. "Modelling of the cellulose and cement mineral bond and the mechanism of aluminous compounds in retarding cement carbonation." Thesis, View thesis, 2001. http://handle.uws.edu.au:8081/1959.7/26659.
Повний текст джерелаАнотація:
Analysis of calcium and oxygen atom arrays of known cement minerals and the structures of cellulose polymorphs were performed to see if it was possible to arrange a cellulose fibre on a cement mineral face such that the fibre is bonded by a repeating array of hydrogen or hydroxide coordination bonds for the full length of the attachment. Of the sixteen important cement minerals modelled, xonotlite, foshagite, tricalcium aluminate hydrate, chondronite and rosenhahnite could form such bonds to modified cellulose fibre. However, this was not the case for other cement minerals, especially tobermorite. Alumium hydroxide, when added to cement-quartz pastes and autoclaved at 180 degrees C, was found to improve the cement's ability to resist carbonation.
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Peng, Joe Zhou. "Modelling of the cellulose and cement mineral bond and the mechanism of aluminous compounds in retarding cement carbonation /." View thesis, 2001. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030714.164824/index.html.
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Tabbert, Toni Raenette. "Verification of the whitetopping thickness design procedure for asphalt concrete overlaid Portland cement concrete pavements." [Ames, Iowa : Iowa State University], 2006.
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Punurai, Wonsiri. "Cement-based materials' characterization using ultrasonic attenuation." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-04042006-171125/.
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Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006.Dr. Jennifer Michaels, Committee Member ; Dr. Jacek Jarzynski, Committee Member ; Dr. Jianmin Qu, Committee Member ; Dr. Laurence J. Jacobs, Committee Chair ; Dr. Kimberly E. Kurtis, Committee Co-Chair.
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Jeffers, Jonathan. "In silico simulation of long term cement mantle failure in total hip replacement." Thesis, University of Southampton, 2005. https://eprints.soton.ac.uk/388231/.
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Hajsadeghi, M. "Engineered structural fibres as replacement for traditional reinforcements for concrete." Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3021280/.
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Milnes, Kathryn. "The influence of cement and aggregate identity on concrete performance." Thesis, Keele University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341300.
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Boukendakdji, Mustapha. "Mechanical properties and long-term deformation of slag cement concrete." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236998.
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Tasong, William Ajua. "Geotechnical controls on aggregate-cement paste interfacial zone in concrete." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252048.
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Li, Xincheng. "Mechanical properties and durability performance of reactive magnesia cement concrete." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607703.
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