To see the other types of publications on this topic, follow the link: Mineral Admixture.
Dissertations / Theses on the topic 'Mineral Admixture'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 41 dissertations / theses for your research on the topic 'Mineral Admixture.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Adjoudj, Mhamed. "Effet des additions minérales et organiques sur le comportement rhéologique du béton." Thesis, Cergy-Pontoise, 2015. http://www.theses.fr/2015CERG0784/document.
Full textAbstract:
L'emploi de certaines additions minérales et organiques dans la confection du mortier et du béton contribue à une modification du processus d'hydratation du ciment. L'incorporation de ces additions minérales entraîne également une modification de la distribution granulaire, l'apparition de nouveaux sites de nucléation et une nouvelle activité des surfaces des grains. Ceci nécessite le malaxage avec des superplastifiants qui viennent défloculer les grains, libérer l'eau piégée dans les interstices et améliorer l'ouvrabilité du béton. Ces modifications des propriétés physicochimiques des composants du béton affectent directement les propriétés rhéologiques du mortier et du béton à l'état frais ainsi que ses composantes finales.L'objectif principal de ce travail est focalisé sur la prédiction des modifications rhéologiques apportées par les additions minérales aux mortiers afin de trouver les meilleures compositions d'une mise en œuvre convenable. Une étude expérimentale est entamée sur des mortiers normalisés où le ciment ordinaire est substitué partiellement par différentes additions minérales telles que la fumée de silice, le laitier des hauts fourneaux, la pouzzolane naturelle et le calcaire. Avec l'eau de gâchage, on a ajouté plusieurs types de superplastifiants avec différents dosages où les paramètres rhéologiques du mortier ont été mesurés respectivement par un mini cône et un rhéomètre.Les paramètre rhéologiques obtenus varient sensiblement avec chaque type d'addition minérale et dépendent de ses propriétés et son interaction avec le superplastifiant et les grains de ciment. Le superplastifiant à base de polycarboxylates est plus efficace en présence du ciment contenant du calcaire ou du laitier conduisant à une amélioration des propriétés rhéologiques. Par contre, le mortier devient plus visqueux s'il contient un fort pourcentage de pouzzolane naturelle. Une relation mathématique est proposée qui exprime la variation de chaque paramètre rhéologique selon le taux de substitution du ciment et le dosage en superplastifiant. Cette relation est exprimée par le produit de trois paramètres; l'effet de l'addition minérale, l'effet du superplastifiant et l'effet de leur interaction. Les coefficients de corrélation trouvés sont proches de l'unité et justifient bien la convenance de ce choix. L'application de cette nouvelle relation à d'autres résultats trouvés par d'autres chercheurs présente une grande satisfaction avec des résultats satisfaisant et des coefficients de corrélation allant 0,9 à 0,98<br>The use of some organic and inorganic admixtures in the production of mortar and concrete contributes to a change in the cement hydration process. The incorporation of these mineral additions also causes a change in the grain distribution, the appearance of new nucleation sites and a new activity of the grain surfaces. This requires mixing with superplasticizers which deflocculates grains, releases the trapped water in the interstices and improves the workability of concrete. These changes in the physicochemical properties of the cement paste directly affect the rheological properties of mortar and concrete in the fresh state and its final components.The main objective of this work is focused on the prediction of rheological changes of mineral additions mortars and finds the best composition for a suitable casting. An experimental study is underway on standardized mortars where ordinary cement is partially substituted by different mineral additions such as silica fume, blast furnace slag, natural pouzzolan and limestone powder. With the mixing water, was added several types with different dosages of superplasticizers where the rheological parameters of the mortar were measured respectively by a rheometer apparatus and a mini cone test.The Theological parameters obtained vary with each type of mineral addition and depend on its properties and its interaction with the superplasticizer and cement grains. The polycarboxylate superplasticizer is more effective in the presence of limestone powder or cement containing slag resulting in improved rheological properties. However, the mortar becomes more viscous if it contains a high percentage of natural pozzolan. A mathematical relationship is provided which expresses the variation of each rheological parameter according the substitution rate of the cement and superplasticizer dosage. This relationship is expressed by the product of three parameters; the effect of the mineral addition, the effect of the superplasticizer and the effect of their interaction. The correlation coefficients found are close to unity and well justify the appropriateness of this choice. The application of this new relationship to other results found by other researchers has high satisfaction with satisfactory results and correlation coefficients ranging from 0.9 to 0.98
2
Yazan, Kazim. "Effects Of Retempering With Superplasticizer On Properties Of Prolonged Mixed Mineral Admixture Containing Concrete At Hot Weather Conditions." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12606751/index.pdf.
Full textAbstract:
Concrete which is manufactured in a mixing plant to be delivered to construction site in unhardened and plastic stage is called ready-mixed concrete. Because of technical and economical reasons, many mineral and chemical admixtures are used in ready-mixed concrete production.
As a result of extra mixing and delayed placing of ready-mixed concrete (especially at hot weather conditions), there can be many problems about concrete, like slump loss.
Addition of water for retempering concrete is the usual procedure, but addition of water without proper adjustment in mixture proportions, adversely affects compressive strength.
During this study, effects of prolonged mixing and retempering with superplasticizer on properties of fresh and hardened concrete at hot weather conditions are observed. Some of the properties of concrete inspected are compressive strength, splitting tensile strength, slump and air content. All mixes contain air entrainer and water reducer at a standard amount. The difference between mixes comes from kind and amount of mineral admixture which cement is replaced by. During the study, fly ash, blast furnace slag, ground clay brick and natural pozzolan are used at amounts, 25% and 50% of cement. Also, a mixture of pure cement is prepared as control concrete.
15 cm initial slump is planned in the experimental work. After five minutes and at the end of first, second, third and fourth hours of mixing process, if needed retempering process is proceeded with superplasticizer and samples are taken. As a result of retempering with superplasticizer, the aimed slump values are obtained. The effects are than, observed.
As a result of this study, it has been observed that replacing Portland cement with certain mineral admixtures, especially fly ash at certain amounts, can be a solution for slump loss problem, by retarding the slump loss effect of prolonged mixing. Also it has been seen that ground clay brick causes better performance for slump values at lateral stages of mixing with respect to pure Portland cement. Another important observation has been about the increase in the amount of air caused by air entraining admixtures in fresh concrete based on prolonged mixing at hot weather conditions.
3
Christianto, Heru Ari. "Effect Of Chemical And Mineral Admixtures On The Fresh Properties Of Self Compacting Mortars." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605322/index.pdf.
Full textAbstract:
Fresh properties of mortars are important factors in altering the performance of self compacting concrete (SCC). Measurement of the rheological properties of the fine mortar part of concrete is generally used in the mix design of SCC. It can be stated that SCC rheology can be optimized if the fine mortar part of concrete is designed properly. However, measurement of the rheological properties is often impractical due to the need for complex equipment. Therefore, more practical methods of assessing mortar workability are often preferred.
In this study, four mineral admixtures, three superplasticizers (SP) and two viscosity modifying admixtures (VMA) were used to prepare self compacting mortar (SCM). The mineral admixtures included fly-ash, brick powder, limestone powder, and kaolinite. Two of the SPs were polycarboxylate based and another one was melamine formaldehyde based. One of the viscosity modifying admixtures was based on an aqueous dispersion of microscopic silica and the other one was based on high molecular weight hydroxylated polymer.
Within the scope of the experimental program, 43 mixes of SCM were prepared from different materials with keeping the amount of mixing water constant. Workability of the fresh mortar were determined using V - funnel and slump flow tests. The setting time of the mortars, were also determined. The hardened properties that were determined included the ultrasonic pulse velocity (UPV) and the strength which was determined at 7, 28, and 56 days.
It was concluded that among the mineral admixtures used, only fly-ash and limestone powder increased the workability of the mixes. The two polycarboxylate based SPs yield approximately the same workability and the melamine formaldehyde based SP was not as effective as the other two.
4
Delibas, Tughan. "Effects Of Granulated Blast Furnace Slag Trass And Limestone Fineness On The Properties Of Blended Cements." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614072/index.pdf.
Full textAbstract:
The aim of this research was to determine the effects of the fineness of different mineral additives on loss on ignition, heat of hydration, physical, mechanical and chemical properties of blended cements. For that purpose, portland cement clinker was replaced with granulated blast furnace slag (GBFS), natural pozzolan (NP) and limestone (L) at 6%, 20% and 35% replacement levels. Blended cements containing GBFS and NP were ground to a fineness of 3000, 5000 and 6000 cm2/g. Cements containing L were ground to 3000 cm2/g, 4000 cm2/g and 4500 cm2/g. All of the blended cement types mentioned above were both interground and separately ground to the specified fineness levels. Therefore, a total of 57 different cements were produced. Loss on ignition, heat of hydration, chemical, mechanical and physical analyses were performed on the produced cements. Moreover, the chemical analyses of the cements were obtained for cement particles finer (-45&mu<br>m) and coarser (+45&mu<br>m) than 45 &mu<br>m in order to determine the ingredients of -45 &mu<br>m, which is known to be more reactive.
As a result it was shown that the grindability differences of the cement ingredients affect the properties of blended cements. An increase in the specific surface area increases both the compressive strength and heat of hydration values and adversely affects the loss on ignition
values. The results also showed that if the cement particles were ground finer, it was more prone to moisture which resulted in higher loss on ignition values after longer periods.
5
Ivan, Lukić. "Komparativna analiza osnovnih svojstava konstrukcijskih betona spravljenih sa različitim vrstama lakih agregata." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2015. http://www.cris.uns.ac.rs/record.jsf?recordId=93149&source=NDLTD&language=en.
Full textAbstract:
U disertaciji su prikazani rezultati sopstvenog eksperimentalnog istraživanja na osnovu kojih je izvršena komparativna analiza uticaja različitih vrsta lakih agregata i vrste i količine cementa na osnovna fizičko-mehanička svojstva lakoagregatnih betona. Takođe, analizirana je i mogućnost zamene dela cementa mineralnim dodacima u cilju smanjenja negativnih uticaja proizvodnje betona na životnu sredinu. Rezultati su pokazali da je primenom svih analiziranih vrsta agregata moguće dobiti konstrukcijski lakoagregatni beton, čak i sa manjim količinama cementa, odnosno sa zamenom dela cementa mineralnim dodacima, kao i da je moguće uspostaviti pouzdane korelacione veze između pojedinih svojstava betona i primenjenih komponentnih materijala.<br>In dissertation are presented results of own experimental research of acomparative analysis of the impact of different types of lightweightaggregates and the type and quantity of cement on basic physical andmechanical properties of structural lightweight concrete. Also, the possibilityof replacing part of cement with mineral admixtures is analyzed in order toreduce the negative impact of concrete production on the environment. Theresults showed that it is possible to obtain structural lightweight aggregateconcrete with all types of lightweight aggregates and even with lowerquantities of cement or with a replacement of part of a cement with mineraladmixtures. Also, it is possible to establish a reliable correlation betweencertain properties of concrete and used component materials.
6
Anjos, Marcos Alyssandro Soares dos. "Adi??o do res?duo de biomassa da cana-de-a??car em pastas para cimenta??o de po?os petrol?feros produtores de ?leos pesados." Universidade Federal do Rio Grande do Norte, 2009. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12742.
Full textAbstract:
Made available in DSpace on 2014-12-17T14:07:02Z (GMT). No. of bitstreams: 1
MarcosASA_capa_ate_cap5.pdf: 2919360 bytes, checksum: 8bb04eb85df77f75f3f1de37bbecc19d (MD5)
Previous issue date: 2009-04-02<br>The Potiguar basin has large fields of viscous oil where the used method for recovering is based on vapor injection; this operation is carried out by injecting vapor in the oilwell
directly, without the protection of a revetment through thermal insulation, what causes its dilation and, consequently, cracks in the cement placed on the annular, and lost of hydraulic insulation; this crack is occasioned by the phenomenon of retrogression of the compressive resistance due to the conversion of the hydrated calcium silicate in
phases calcium-rich, caused by the high temperatures in the wells, subjected to thermal recuperation. This work has evaluated the application of composite pastes with addition
of residue of biomass of ground sugar-cane bagasse as anti-retrogression mineral admixture for cementation of oil-wells subjected to thermal recuperation. The addition of the mineral residue was carried out considering a relative amount of 10, 20, 30, 40 and 59% in relation to cement mass, trying to improve the microstructure of the paste, still being developed a reference paste only with cement and a paste with addition of 40% of silica flour - renowned material in the oil industry as anti-retrogression additive. Pozzolanic activity of the ash was evaluated through XRD, TG/DTG, as the resistance
to compression, and it was also determined the physical and mechanical behavior of the pastes when submitted to cure at low temperatures (22 and 38? C); besides it was evaluated the behavior of the pastes when submitted to two cycles of cure at high temperature (280?C) and pressure (7 MPa). It was verified that the ash of the sugar-cane biomass presents pozzolanic reaction and has great efficiency in decrease the
permeability of the paste by filler effect, as well as that addition of ash in a relative amount of 10, 20 e 30% increases cured compressive resistance at low temperatures. It
was also showed that the ash in a relative amount of 40% and 59% has very significant efficiency as anti-retrogression additive, since it prevents the decrease of compressive
resistance and forms hydrated calcium silicate type xenotlita and tobermorita which have more resistance and stability in high temperatures<br>A bacia Potiguar tem grandes campos de ?leo viscoso, onde o m?todo de recupera??o utilizado ? a inje??o de vapor; essa opera??o ? realizada injetando-se vapor diretamente
no po?o, sem a prote??o do revestimento atrav?s de isolamento t?rmico, o que provoca a dilata??o do mesmo, provocando assim falhas no cimento colocado no anular, e
conseq?entemente, perda do isolamento hidr?ulico, esta falha tem origem no fen?meno de retrogress?o da resist?ncia ? compress?o devido a convers?o do silicato de c?lcio
hidratado em fases ricas em c?lcio, provocada pelas elevadas temperaturas nos po?os, sujeitos ? recupera??o t?rmica. O presente trabalho avaliou a aplica??o de pastas comp?sitas com adi??o de res?duos de biomassa do baga?o da cana-de-a??car mo?das como aditivo mineral anti-retrogress?o para cimenta??o de po?os petrol?feros sujeitos a recupera??o t?rmica. A adi??o do res?duo mineral foi realizada teores de 10, 20, 30, 40 e 59% em rela??o a massa do cimento, visando melhorar a microestrutura da pasta, sendo ainda produzidas uma pasta de refer?ncia, apenas com cimento e uma pasta com adi??o de 40% de silica flour material consagrado na ind?stria de petr?leo como aditivo antiretrogress?o. Foram avaliados a atividade pozol?nica da cinza atrav?s de DRX, TG/DTG e resist?ncia ? compress?o, determinando-se tamb?m o comportamento f?sico e mec?nico das pastas submetidas a cura com baixas temperaturas (22 e 38?C), al?m da avalia??o do comportamento das pastas submetidas a dois ciclos de cura a alta temperatura (280?C) e press?o (7 MPa). Verificou-se que a cinza de biomassa da cana apresenta rea??o pozol?nica, tendo grande efici?ncia na diminui??o da permeabilidade da pasta por efeito filler, e que as adi??es de cinza em teores de 10, 20 e 30% aumentam a resist?ncia ? compress?o das pastas curadas a baixas temperaturas. Constatou-se ainda que a cinza em teores de 40% e 59% tem ?tima efici?ncia como aditivo antiretrogress?o, pois evitam a diminui??o da resist?ncia ? compress?o e formam silicato de c?lcio hidratado do tipo xenotlita e tobermorita que se apresentam mais resistentes e est?veis as altas temperaturas
7
劉艷 and Yan Liu. "Preventive effects of mineral admixtures on Alkali-Silica reaction." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31244531.
Full text
8
Darwish, Abdulhanan A. "Development of high performance concrete using combinations of mineral admixtures." Thesis, University of Sheffield, 1995. http://etheses.whiterose.ac.uk/3066/.
Full textAbstract:
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.
9
LIMA, Marcelo Batista. "Avaliação da capacidade de proteção contra a corrosão da arma-dura induzida por cloretos de concretos com adições minerais e inibidores de corrosão." Universidade Federal de Goiás, 2009. http://repositorio.bc.ufg.br/tede/handle/tde/1347.
Full textAbstract:
Made available in DSpace on 2014-07-29T15:18:24Z (GMT). No. of bitstreams: 1
pretextual.pdf: 140883 bytes, checksum: 5d9ee4b9b3884a0032825e604304580f (MD5)
Previous issue date: 2009-09-28<br>Increasing the durability of concrete structural elements is primordial, especially those related to power generation in eolic areas that are subjected to the phenomenon of reinforcement corrosion. In this context, this study aims to evaluate the overall protection ability of concrete to the phenomenon of reinforcement corrosion induced by chlorides. To this end, it was adopted a statistical program based on a fractional factorial design in which the variables studied were as follows: the water-binder ratio (0.35, 0.45 and 0.55), the type of mineral admixture (silica fume and blast furnace slag at specific levels), the type of corrosion inhibitor (calcium nitrite, sodium nitrite and amine) and the level of corrosion inhibitor (minimum and maximum recommended by each manufacturer). In the concrete investigations, the tests performed were corrosion potential, polarization resistance and electrochemical impedance. Throughout the experiments, it was possible to testify the beneficial effect of reducing the water-binder ratio. It was also possible to prove the very positive effect of the incorporation of mineral admixtures, especially of silica fume. The satisfactory performance of various inhibitors evaluated was also verified, specially when concrete contains mineral admixtures. A parallel study was conducted to make a comparative analysis of inhibitors at the same range of concentrations (at solid levels of 0.76%, 2.21% and 3.66% of the compound on the cement mass), nevertheless this study have demonstrated that fixing contents for all inhibitor is not appropriated, and the recommended dosages by the manufacturer is the best condition. As the levels recommended by manufacturers, it was found that the higher percentages have not worked well for sodium nitrite otherwise, for amine and nitrite calcium, the higher levels implied better results. Regarding the tannin inhibitor also assessed in the parallel study mentioned above (related to specific inhibitors), its good performance related to corrosion inhibition happened just for the content of 0.76% (the lowest levels). For the other contents, it was verified anomalous results. These results demonstrated that each type of corrosion inhibitor has its optimal concentration for use in concrete. Based on a cost-benefit analysis and evaluating the increase in the concrete value for cubic meter (in R$) in the presence of inhibitors at the same contents, it was verified a relative parity prices among the tested nitrites and an extremely high cost of amine. However, when performing the same analysis but using the levels recommended by the manufacturers for each inhibitor independent, it was found that the large disparity in prices between nitrite and amine was reduced considerably. An assessment of technical and economic feasibility was also performed based on the efficiency of corrosion inhibition and cost per cubic meter of concrete mixtures that did not show a typical depassivation of their stell bar up to the attack age evaluated<br>O aumento da durabilidade é um aspecto primordial para os elementos estruturais de concreto, em especial aqueles constituintes das estruturas de geração de energia em parques eólicos, sujeitos ao fenômeno de corrosão das armaduras. Nesse contexto, este trabalho tem como objetivo geral avaliar a capacidade de proteção de diferentes concretoS frente ao fenômeno da corrosão da armadura induzida por cloretos. Para tanto, foi adotado um planejamento estatístico baseado em um modelo fatorial fracionado em que as variáveis estudadas foram: a relação água/aglomerante (0,35; 0,45 e 0,55), o tipo de adição mineral (sílica ativa e escória de alto-forno, em teores específicos), o tipo de inibidor de corrosão (nitrito de cálcio, nitrito de sódio e amina) e o teor de inibidor de corrosão (mínimo e máximo recomendado por cada fabricante). Na avaliação dos concretos, foram realizados ensaios de potencial de corrosão, resistência de polarização e impedância eletroquímica. Ao longo de todo experimento foi possível constatar o efeito benéfico da redução da relação a/agl. Também foi possível verificar o efeito extremamente positivo da incorporação das adições minerais, em especial da sílica ativa. Constatou-se também o efeito positivo dos diversos inibidores avaliados, em seus teores mínimo e máximo, beneficio que se mostrou mais pronunciado quando da utilização conjunta com as adições minerais. Um estudo paralelo foi realizado para se fazer uma análise comparativa dos inibidores dentro da mesma faixa de teores empregados (teores de 0,76%; 2,21% e 3,66% de sólidos do aditivo em relação à massa de cimento), no qual se verificou que a utilização desses teores fixos para os diferentes tipos de inibidores não se mostrou tão eficiente quanto em relação à utilização dos aditivos na dosagem de recomendação do fabricante. Quanto a estes teores (recomendados pelos fabricantes), verificou-se que os percentuais mais altos não funcionaram bem para o nitrito de sódio, ao passo que para a amina e para o nitrito de cálcio os teores mais elevados resultaram em melhores resultados. Em relação ao tanino, inibidor que também foi avaliado no estudo paralelo referido anteriormente (específico sobre os inibidores), só houve algum resultado de inibição de corrosão para o teor de 0,76% (mais baixo dos teores), tendo-se obtido resultados anômalos para os outros 2 teores mais altos. Tais resultados permitiram constatar que cada tipo de inibidor de corrosão possui sua concentração ótima de utilização no concreto. Fazendo-se uma análise de custo e avaliando-se o acréscimo em Reais no valor do m3 do concreto proporcionado pelos diversos aditivos inibidores e nos teores de mesma faixa de emprego, verificou-se uma relativa paridade de preços entre os nitritos e um elevadíssimo custo da amina. No entanto, ao se realizar a mesma análise, mas utilizando os teores recomendados pelos fabricantes de cada inibidor, verificou-se que a grande disparidade de preços entre os nitritos e a amina foi reduzida de forma considerável. Uma avaliação da viabilidade técnico-econômica dos concretos também foi realizada, a partir dos dados de eficiência de inibição à corrosão e custo/m3 das misturas que não apresentaram comportamento típico de despassivação de suas armaduras até a idade de ataque considerada
10
Tran, Victor. "Effect of Mineral and Chemical Admixtures on Durability of Cementitious Systems." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/6040.
Full textAbstract:
Mineral and chemical admixtures are used today in almost all concrete mixtures to improve concrete fresh and hardened properties, and to enhance concrete durability. In this study, four mineral and four chemical admixtures were investigated: namely, metakaolin (MK), silica fume (SF), Class F fly ash (FA), blast-furnace slag (BFS), two high-range water reducers (SP), water reducer/retarder (WRD), and air-entrainer (AEA). The objective of this study is to assess the effects of commonly used mineral and chemical admixtures on the durability of the cementitious system. Two durability issues were addressed in this study: the potential of the cementitious system to generate heat, and sulfate durability. The properties studied here included heat of hydration (HOH) measurements using isothermal calorimetry, setting properties, compressive strength, and expansion on exposure to a sodium sulfate solution. X-ray diffraction was used to characterize the as-received materials and explain failure trends.
The findings of this study indicate that silica fume inclusion sustains superior durability in comparison to the other mineral admixtures considered here. Replacement levels as low as 10% outperformed the other admixtures studied. Fly ash showed improvement in the workability of the mixes, but had the lowest compressive strength results and might pose challenges when the rate of strength gain is critical. However, Class F fly ash mixtures showed better performance than unblended mixtures when exposed to a sulfate source. Metakaolin mixes showed higher heat evolution among all the mixtures studied here. This can potentially lead to durability concerns, especially when temperature rise is a design concern. Blast-furnace slag also improved the workability of the mixes and the later compressive strength, but had mixed performances when examined for sulfate durability.
11
Meyerson, Richard. "Compressive Creep of Prestressed Concrete Mixtures With and Without Mineral Admixtures." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/31525.
Full textAbstract:
Concrete experiences volume changes throughout its service life. When loaded, concrete experiences an instantaneous recoverable elastic deformation and a slow inelastic deformation called creep. Creep of concrete is composed of two components, basic creep, or deformation under load without moisture loss and drying creep, or deformation under drying conditions only. Deformation of concrete in the absence of applied load is often called shrinkage.
The deformation due to creep is attributed to the movement of water between the different phases of the concrete. When an external load is applied, it changes the attraction forces between the cement gel particles. This change in the forces causes an imbalance in the attractive and disjoining forces. However, the imbalance is gradually eliminated by the transfer of moisture into the pores in cases of compression, and away from the pores in cases of tension.
Designs typically use one of the two code models to estimate creep and shrinkage strain in concrete, ACI 209 model recommended by the American Concrete Institute or the CEB 90 Eurocode 2 model recommended by the Euro-International Committee. The ASSHTO LRFD is based on the ACI 209 model. Three other models are the B3 model, developed by Bazant; the GZ model, developed by Gardner; and the SAK model developed by Sakata.
The development of concrete performance specifications that limit the amount of compressive creep of concrete mixtures used by the Virginia Department of Transportation, specifically concrete mixtures used for prestressed members (A-5 Concrete) were assessed, along with determining the accuracy and precision of the creep models presented in the literature.
The CEB 90 Eurocode 2 model for creep and shrinkage is the most precise and accurate predictor. The total strain for the VDOT portland cement concrete mixtures discussed in this study were found to be between 1200 ± 110 microstrain at 28 days, and 1600 ± 110 microstrain at 97 days, at a five percent significant level.<br>Master of Science
12
Bertin, Matthieu. "L’impact du séchage au jeune âge sur la carbonatation des matériaux cimentaires avec additions minérales." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1034/document.
Full textAbstract:
De nos jours, l’utilisation de liants à faible teneur en clinker est de plus en plus courante. Or la cinétique de réaction des additions minérales utilisées est plus lente que celle du clinker. Si les conditions de cure ne sont pas adaptées, le matériau aura une structure poreuse plus importante, ce qui le rendra plus sensible à la pénétration des agents agressifs extérieurs comme le CO2 ou les Cl-. La carbonatation du béton est l’un des principaux phénomènes pouvant diminuer la durée de vie d’une structure en béton armé. En effet, elle entraine une diminution du pH de la solution interstitielle qui a pour conséquence une dépassivation des armatures, puis la corrosion de ces dernières si les conditions s’y prêtent.L’objectif de cette thèse est d’étudier l’impact de la carbonatation au jeune âge sur des liants à faible teneur en clinker. Pour cela l’étude se compose de deux aspects : le premier est l’étude de l’impact de l’hydratation et de la carbonatation sur les propriétés de transport et les isothermes de sorption hydrique, et le second est l’étude de l’impact du couplage hydratation-séchage-carbonatation sur la microstructure et la structure poreuse. Pour le premier aspect, les propriétés de transport étudiées sont la diffusion de l’O2, la diffusion de la vapeur d’eau, la perméabilité à l’eau liquide qui sont des données d’entrée dans les modèles de carbonatation ainsi que la perméabilité aux gaz qui est un indicateur de durabilité. Pour le second aspect, l’impact du couplage est mesuré par ATG et DRX pour déterminer l’assemblage de phases, de plus de la porosimétrie par intrusion de Mercure et des pesées hydrostatiques sont effectuées pour détecter le changement de la structure poreuse. Les matériaux étudiés sont des pâtes de ciment et des bétons avec un rapport eau/ liant de 0,57 avec l’un des trois liants suivants : CEM I, CEM I +30% de cendres volantes et CEM I +60% de laitiers.Pour le premier aspect, les résultats montrent que pour les pâtes de CEM I le temps de cure a un faible impact sur les isothermes de sorption de vapeur d’eau s’il est compris entre 3 jours et 6 mois. Alors que, pour les pâtes de CEM I + 60% de laitier, l’augmentation du temps de cure accroit significativement la teneur en eau (pour HR=65%, tcure=3 jours et pour tcure=6 mois ) dû à une augmentation de la teneur en C-S-H. D’autre part, la carbonatation entraine une diminution de la teneur en eau de l’échantillon, ainsi que l’amplitude de l’hystérésis. De plus, le gel a une porosité plus grossière. Par ailleurs, la carbonatation entraine une augmentation de la perméabilité aux gaz des matériaux. Pour le second aspect, les résultats montrent que l’utilisation d’additions minérales diminue la résistance à la carbonatation du matériau et que cette résistance augmente avec le temps de cure si l’échantillon contient des additions. La carbonatation de la portlandite, des C-S-H et des aluminates est concomitante. De plus, pour les matériaux aux laitiers, les résultats montrent qu’ils sont plus sensibles à la carbonatation des C-S-H et des aluminates que les CEM I. En effet quand le rapport variation molaire de CaCO3 sur variation molaire de Portlandite est calculé, il vaut 1.8 pour le CEM I et environ 3.5 pour les matériaux aux laitiers. Enfin, la carbonatation entraine une diminution du degré de saturation de l’échantillon. En effet, le degré de saturation à la surface de l’échantillon passe de 50% à 35% après carbonatation pour les échantillons de CEM I et de 50% à 5% pour les échantillons de CEM I + 60% de laitiers. Cette diminution peut s’expliquer par la diminution de la surface spécifique qui est divisée par 2 après carbonatation due à la décalcification des C-S-H. Même si la carbonatation entraine une diminution de porosité cette dernière est trop faible dans ce cas pour contrer cet effet<br>Nowaday, low clinker content binders are used more and more often. But the kinetics reactions of the supplementary cementitious materials (SCM) are slower than this one of clinker. If the curing conditions are not adapted, material will have a bigger pore structure and becomes more sensitive to the ingress of aggressive species from the environment like the CO2 or Cl-. Carbonation is one of main phenomena which can lead to decrease the life time of reinforced concrete structure. Indeed, it leads to a decrease of pore solution pH which leads to the depassivation of rebar. Then these rebars can be corroded if the conditions are appropriate.The aim of this thesis is to study the impact of carbonation at early age for binder with a low clinker content. This study was composed of two aspects: the first one is focus on the impact of hydration and carbonation on the transport properties and the water vapour sorption isotherms (WVSI), and the second one is focus on the impact of coupling hydration – drying-carbonation on the microstructure and the pore structure. For the first aspect, the studied transport properties was O2 diffusivity, water vapour diffusivity, water liquid permeability which are inputs for carbonation modelling and the intrinsic gas permeability which is a durability factor. For the second aspect, the coupling impact was measured by TGA and DRX to determine the phase assemblage; moreover Mercury intrusion porosimetry (MIP) and hydrostatic weigh were carried out to measure the change in the pore structure. The studied materials were cement pastes and concretes with water to binder ratio of 0.57 with one of the following binders: CEM I, CEM I +30% PFA and CEM I + 60% GGBS.For the first part, results show that a curing time between 3 days and 6 months has a low impact on the WVSI for the CEM I paste. Whereas, in the CEM I +60% GGBS paste, when the curing time increases, the water content increases (for a RH=65%, tcuring=3 days and for tcuring=6 months ), this is due to the increase of the C-S-H content. Moreover, carbonation leads to decrease the water content and the hysteresis becomes flat. Additionally, carbonation leads to increase the intrinsic gas permeability. For the second part, the results show that the use of SCM decreases the carbonation resistance and this resistance increases with the curing time. Carbonation of Portlandite, C-S-H and aluminates occurs in the same time. Moreover, the CEM I +60% GGBS paste are more sensitive to the carbonation of C-S-H and aluminates than the CEM I paste. Indeed, the molar variation of CaCO3 to the molar variation of Portlandite ratio has a value around 3.5 for the CEM I +60% GGBS and 1.8 for the CEM I. Finally, carbonation leads to decrease the water saturation degree at the surface of sample. Indeed, the degree of saturation at the surface of the sample increases from 50% to 35% after carbonation for the CEM I paste and from 50% to 5% for the CEm I +60% GGBS paste. This decrease can be explained by the decrease of the BET specific surface which is divided by 2 after carbonation. It is due to the decalcification of C-S-H. Although carbonation leads to a decrease of porosity, this one is too small in this case to counter this effect
13
Xu, George Jianzhou. "Influence of PSMC and other mineral admixtures on the properties of cement mortar." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30300.pdf.
Full text
14
Ustuner, Didem Tugba. "Effectiveness Of Set Accelerating Admixtures With Different Cement Types." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12611011/index.pdf.
Full textAbstract:
Accelerating and mineral admixtures, one of the major ingredients in concrete, are primarily used to modify the properties of both fresh and hardened concrete.
Within the scope of this thesis, there were four types of cements having almost identical fineness. The mixes were prepared by using natural pozzolan, blast furnace slag and limestone conforming to TS EN 197-1 and two types of accelerating admixtures, namely triethanolamine (TEA) and calcium formate (CF).
The effect of set accelerating admixtures with different cement types on the setting time, water demand and compressive strength has been analyzed by an experimental study in accordance with relevant ASTM standards.
Finally, it has been observed that the amount of the accelerating admixtures used is suitable because of their effects on the water demand, setting and strength. Due to the density difference of mineral admixtures and clinker, the normal consistency and 110% flow water content should be considered on a volumetric basis. The effectiveness of the accelerating admixtures on the normal consistency water, 110% flow water content and setting time depends on the type and amount of mineral admixtures. The increase caused by CF in the normal consistency and 110% flow water content is higher than that by TEA. The accelerating effect of TEA and CF on the setting times is more significant for cements incorporating 6% mineral admixture. The effects of accelerating admixtures on the compressive strength change with specimen age, type and amount of mineral admixtures. Generally, for all cement types, early age compressive strengths increase with the increase of TEA, however long term strengths increase by increasing CF.
15
Tran, Duc Long. "Impact of intrinsic granular porosity on the durability properties of concrete." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30021.
Full textAbstract:
La préservation des ressources naturelles et la limitation des émissions de CO2 sont une contribution au développement durable. Dans le cadre de la conception du béton, cette contribution consiste à utiliser des granulats locaux ou recyclés. Cependant, ces derniers peuvent être poreux et de faible qualité. La communauté scientifique est d'accord sur le fait que la porosité intrinsèque des granulats modifie les propriétés de transport du béton, mais dans quelle mesure reste une question. L'objectif de la thèse est d'analyser l'impact de la porosité intrinsèque des granulats grossiers, principalement sur les propriétés de durabilité du béton. Dans une compréhension préliminaire et en vue d'accentuer les phénomènes se produisant dans le béton, un programme expérimental est conçu pour le modèle élémentaire (EM), qui est composé de pâte et de gravier. L'impact de la nature des granulats (poreux et non poreux), de l'état d'humidité et du volume ainsi que de la nature du liant, est analysé sur i) la porosité de l'eau du modèle élémentaire, ii) la structuration de l'interface pâte-granulat. Ensuite, à l'échelle du béton, les matériaux ont été conçus avec le même squelette de granulats (même sable) et la même teneur équivalente en liant. Les conceptions variaient selon la nature des granulats, l'état d'humidité, la nature du liant, la variation du rapport eau/ciment et l'incorporation d'adjuvants chimiques (plastifiant ou superplastifiant). L'impact de la porosité des granulats grossiers sur les propriétés à l'état frais (affaissement, densité apparente et teneur en air emprisonné) et à l'état durci (résistance à la compression, porosité de l'eau, absorption d'eau, perméabilité aux gaz, migration des chlorures, carbonatation accélérée et teneur en portlandite) a été étudié. Les principaux résultats montrent que l'état d'humidité des agrégats et la nature du liant sont les premiers facteurs qui conditionnent la structuration de l'interface pâte/agrégats au sein du modèle élémentaire. La nécessité d'utiliser des agrégats poreux en surface saturée et sèche est particulièrement mise en évidence. À l'échelle du béton, les propriétés à l'état frais sont influencées par la porosité des granulats et le rapport eau/liant (W/B). Cependant, pour un rapport eau/liant fixe correspondant à une consistance fluide, les variations des propriétés à l'état frais mesurées lors de l'incorporation de granulats poreux ne dépendent pas de la nature du liant. Dans le béton durci, la porosité des granulats joue un rôle important dans la porosité de l'eau et la perméabilité à l'air du béton, quelle que soit la nature du liant. Pour les autres propriétés de durabilité (absorption d'eau, migration de Clo, carbonatation et résistance à la compression), la nature du liant l'emporte sur la porosité des granulats<br>The preservation of natural resources and the limitation of CO2 emissions are a contribution to sustainable development. In the context of the concrete design, this contribution consists in using local or recycled aggregates. However, local or recycled aggregates can be porous and of low quality.The scientific community agrees that the intrinsic porosity of aggregates changes the transport properties of concrete, but to what extent is still a question. The objective of the thesis is to analyze the impact of intrinsic coarse aggregate porosity on mainly the durability properties of concrete. In a preliminary understanding and with a view to accentuating phenomena occurring in the concrete, an experimental program is designed for elementary model (EM), which is composed of paste and gravel. The impact of the aggregate nature (porous and non-porous), moisture state and volume together with the binder nature, is analyzed on i) the water porosity of EM, ii) the structuration of the paste-aggregate interface. Next, at concrete scale, materials were designed with the same skeleton of aggregates (same sand) and the same equivalent binder content. The designs varied by the aggregate nature, moisture state, the binder nature, the variation of water/cement ratio and the incorporation of chemical admixtures (plasticizer or superplasticizer). The impact of coarse aggregate porosity on properties in the fresh state (slump, apparent density and entrapped air content) and in the hardened state (compressive strength, water porosity, water absorption, gas permeability, chloride migration, accelerated carbonation and Portlandite content) was studied. The main results show that the moisture state of aggregate and the binder nature are the first factors that condition the structuring of the paste/aggregate interface within the elementary model. The necessity to use porous aggregates in saturated surface dry is particularly highlighted. At the scale of concrete, the properties in the fresh state are influenced by the aggregate porosity and the water/binder (W/B) ratio. However, for a fixed W/B ratio corresponding to fluid consistency, the variations in the fresh properties measured when porous aggregates are incorporated do not depend on the binder nature. In hardened concrete, porosity of aggregate plays an important role in water porosity and air permeability of concrete whatever the nature of binder. For other durability properties (water absorption, Clo migration, carbonation and compressive strength), the nature of binder overcome leading in comparison to the porosity of aggregate
16
Santos, Sérgio Botassi dos. "Análise da fluência do concreto massa nas primeiras idades de carregamento : influência de aditivos plastificantes e adições minerais." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/35633.
Full textAbstract:
Estruturas de concreto mais arrojadas têm sido executadas ao longo das últimas décadas, utilizando-se de projetos e técnicas construtivas cada vez mais avançadas, às quais, por sua vez, procuram manter a qualidade na execução da obra e proporcionar maior durabilidade e rapidez na entrega do empreendimento. Dentro deste contexto evolutivo, também se enquadra a tecnologia do concreto, incluindo o estudo dos efeitos de seus materiais constituintes (agregados, aglomerantes, aditivos, adições, etc) sobre as mais diversas propriedades do concreto. Frente a este desafio, a tese se propõe a contribuir de maneira planejada na avaliação de como algumas adições minerais e os aditivos plastificantes podem afetar as propriedades do concreto, com ênfase dada à fluência nas primeiras idades de início de carregamento. A fluência além de ser de difícil obtenção de resultados em laboratório é uma propriedade que possui sua complexidade associada às diversas variáveis intervenientes no fenômeno e ainda ao seu mecanismo de atuação, o qual não é totalmente compreendido. A atual bibliografia sobre o assunto tem se mostrado incipiente e algumas vezes contraditória nos trabalhos disponíveis, principalmente quando se refere aos efeitos na fluência nas primeiras idades, apesar dos esforços depreendidos por pesquisadores consagrados desde a década de 30 do século passado. Assim, surgiu a necessidade de se delimitar a pesquisa a partir de um programa experimental capaz de avaliar, mesmo que ainda restrito a uma amostra de materiais e dosagem limitada, mas que permita uma visão geral de como as adições e os aditivos interagem no comportamento da fluência. O programa experimental compreenderá basicamente na avaliação matricial das possíveis combinações das adições minerais: metacaulim, escória de alto-forno e argila calcinada, associadas aos aditivos plastificantes, base lignossulfonato e naftaleno, sobre a fluência do concreto nas idades iniciais de carregamento de 1, 3 e 7 dias, e ainda sobre outras propriedades mecânicas, elásticas e térmicas, também nas idades de 14 e 28 dias. Os resultados demonstram que tanto as adições minerais estudadas como os aditivos plastificantes e suas combinações, avaliados por meio da análise estatística de variância, interferem decisivamente no comportamento da fluência, mesmo mantendo o proporcionamento dos materiais inalterados em relação à referência. A idéia é de que esta pesquisa contribua para a atualização dos padrões normativos atuais sobre o assunto, e que estimule futuras pesquisas para detalhar o efeito de outras adições e aditivos químicos sobre a fluência e também sobre uma série de traços de concreto e condições além das abordadas nesta tese.<br>Bolder concrete structures have been performed in the past decade. They use increasingly advanced building projects and techniques which, in turn, aim at keeping work quality and providing higher durability and quicker project completion. Concrete technology also has a role this evolutionary setting. It studies the effects of its component materials (aggregates, binders, chemical and mineral admixtures, etc.) on various concrete properties. In face of this challenge, this thesis aims at contributing to a planned assessment of how some mineral and chemical admixtures can affect concrete properties, mainly regarding creep at early ages at loading. Besides being difficult to assess through laboratorial testing, creep is a property whose complexity is associated to several intervening variables and to its working mechanisms, which are not fully understood. The current relevant literature has shown to be incipient and sometimes contradictory concerning the available studies, mainly those referring to the effects of creep at early ages, despite the efforts renowned researchers have made since the 1930s. This explains the need of limiting the investigations to an experimental program which is able to assess, even if restricted to a sample of materials and limited mix proportion, but also allow an overview of how mineral and chemical admixtures interact creep behavior. For assessing the possible mineral admixture combinations, this experimental program will comprise basically: metakaolin, blast furnace slag, and calcined clay associated to lignosulfonate and naphthalene-based admixtures on concrete creep at ages of loading 1, 3, and 7 days, as well as on other mechanical, elastic, and thermal properties, at ages 14 and 28 days. The results show that both mineral and chemical admixtures and their combinations, assessed in this study through statistical analysis of variance, significantly interfere in creep behavior, even though material proportion remains unchanged compared to the reference concrete mix. The idea is that this research can contribute to update the current standards in this field, and stimulate future studies detailing the effect of other mineral and chemical admixtures on creep and also on other concrete mixes and conditions that have not been approached in this study.
17
Zemajtis, Jerzy. "Modeling the Time to Corrosion Initiation for Concretes with Mineral Admixtures and/or Corrosion Inhibitors in Chloride-Laden Environments." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30721.
Full textAbstract:
The application of a mineral admixture, or a corrosion inhibitor, or a combination of both are methods used for the corrosion protection for reinforced concrete bridges. The results of a study on evaluation of corrosion inhibitors from three different manufacturers and of concretes with fly ash, slag cement, and silica fume and a concrete with silica fume and a corrosion inhibitor are presented. The specimens were built to simulate four exposure conditions typical for concrete bridges located in the coastal region or inland where deicing salts are used. The exposure conditions were horizontal, vertical, tidal, and immersed zones. The specimens were kept inside the laboratory and were exposed to weekly ponding cycles of 6% (w/w) sodium chloride solution. In addition, cover depth measurements from 21 bridge decks and chloride data from 3 bridge decks were used, together with laboratory data, in modeling the service lives of the investigated corrosion protection methods.
The methods used to assess the condition of the specimens included chloride concentration measurements, corrosion potentials, and corrosion rates (3LP). Additionally, visual observations were performed for identification of rust stains and cracking on concrete surfaces.
Modeling the time as a function of probability of the end of functional service life (EFSL) is presented. It has been shown that the distributions of surface chloride concentration, C0, and diffusion coefficient, Dc, are key elements in the model. Model predictions show that the concretes with mineral admixtures provide much better level of protection against moisture and chlorides than the ordinary portland cement concrete alone. Application of a corrosion inhibitor causes an elevation of the chloride threshold resulting in an additional increase in time to EFSL.
More field studies are needed to better estimate distributions of surface chloride concentration and diffusion coefficient of Virginia bridge decks, and to confirm predicted times to EFSL for low permeable (LP) concretes.<br>Ph. D.
18
McDonnell, Thomas Francis. "EFFECT OF MINERAL ADMIXTURES AND COARSE AGGREGATE SIZE ON COMPRESSIVE STRENGTH AND FREEZE-THAW RESISTANCE OF PORTLAND CEMENT CONCRETE." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1177510051.
Full text
19
Möschner, Göril. "A thermodynamic approach to cement hydration : the role of retarding admixtures and Fe-minerals during the hydration of cements /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17422.
Full text
20
Pikna, Ondřej. "Studium možností redukce objemových změn a vývoje hydratačních teplot v betonech." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392333.
Full textAbstract:
Volume changes are one of the priority characteristics of concrete that plays an important role place mainly in the durability of structures as such. These low volume changes are required especially for structures as: industrial concrete floors, massive structures and waterproof structures. One of the possibilities in reducing these changes is the use of mineral admixtures with suitable grain curve of aggregate. Another possibility is the use of shrinkage reducing admixtures. There can occur problem with efficiency (long term age) with other components of the mixture. Therefore, the effort of this work is to use the avaible processes for maximum reduction of shrinkage and hydration temperatures.
21
Lima, Sofia Araújo. "Análise da viabilidade do uso de cinzas agroindustriais em matrizes cimentícias: estudo de caso da cinza da casca da castanha de caju." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18141/tde-10072008-172206/.
Full textAbstract:
Atualmente, o aproveitamento de resíduos na construção civil tem sido estimulado devido essa atividade ser um dos maiores consumidores de materiais naturais em seus processos e produtos. As cinzas agroindustriais ocupam lugar de destaque dentre os resíduos com possibilidades de aplicação em materiais cimentícios, pois algumas, como a cinza da casca do arroz, apresentam propriedades pozolânicas, contribuindo para a redução do consumo de cimento Portland. Nesse sentido, esta pesquisa teve como objetivo principal a avaliação da viabilidade técnica do uso de cinza agroindustriais em matrizes de cimento Portland, tendo como estudo de caso a cinza da casca da castanha de caju (CCCC). As cascas das castanhas de caju, resíduos da produção das castanhas, são incorporadas novamente ao processo, e, nas caldeiras, irão gerar calor para a decorticação de novas castanhas. A CCCC é o resíduo colhido no fundo da grelha das caldeiras, resultante da queima das cascas de castanhas. Atualmente, esse resíduo é utilizado como adubo em plantações de caju, sendo uma pequena parte destinada à aterros sanitários comuns. Foram realizados ensaios para avaliar a composição físico-química da CCCC; analisar o potencial pozolânico; analisar a retração por secagem e da profundidade de carbonatação de argamassas confeccionados com CCCC; e determinar a capacidade de estabilização/solidificação da CCCC pela matriz cimentícia. A partir dos resultados, pode-se apontar como características principais da CCCC: i) não apresentar potencial pozolânico; ii) favorecer a incorporação de ar em matrizes cimentícias; iii) ocasionar solubilidade de metais pesados e Fenol quando no estado in natura; iv) contribuir para o aumento da retração por secagem e da carbonatação em argamassas; v) liberar Cromo e Sódio mesmo quando estabilizada/solidificada em pastas em teores de até 10% de substituição. Por essas considerações, a CCCC não apresentou viabilidade técnica para uso em matrizes cimentícias.<br>Nowadays, the use of wastes on civil building has been stimulated for it to be one of most consumers of raw materials in their processes and products. The agroindustrial ashes have a prominent place among the wastes with possibilities of application in cementitious materials, because some ashes, such rice husk ash, have pozzolanic activity, and they contribute to reduce the Portland cement consumption. This work aimed to study the evaluation of technical feasibility of the agroindustrial ashes for use in Portland cement matrices, using the ash of the rind of the cashew nut (ARCN) as case study. The rinds of cashew nut (wastes of nuts\' production) are burned again during the heating process, and in boilers, they will generate heat for shelling other nuts. The ARCN is the waste collected from the boiler grid, resulted from burning of the rind of nuts. This waste is used as compostes in plantings of cashew and a little part of it is dumped in landfill sites. Tests were made for evaluation of physico-chemical composition of ARCN; for analyse of pozzolanic activity; for analyse of drying shrinkage and carbonation in mortars made with ARCN; and the analyse of the stabilization/solidification of ARCN in pastes. After the analyse of results, it may be pointed as main features of ARCN: i) not show pozzolanic activity; ii) to promote air entrainment in cementitious matrices; iii) to cause heavy metals and Phenol solubilization as in raw state; iv) to increase the drying shrinkage and carbonation in mortars; and, v) to let out Chrome and Sodium when stabilizated/solidificated in pastes in levels of replacement until 10%. For all these considerations, the ARCN haven\'t showed technical feasibility for use in cementitious matrices.
22
Allahyari, Ilgar. "Approche performantielle des bétons : vers une meilleure caractérisation des indicateurs de durabilité." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30119/document.
Full textAbstract:
La fabrication du ciment, par sa phase de clinkérisation, est très énergivore et émet une quantité importante de gaz à effet de serre dans l'atmosphère. En effet, la production d'une tonne de clinker génère environ une tonne de CO2. Afin de réduire ces émissions, une des alternatives est l'utilisation des additions minérales dans la confection des bétons en remplacement partiel du ciment. Cette substitution apparait comme une des solutions les plus efficaces permettant à la fois de diminuer l'énergie consommée et de réduire le dégagement de CO2 dans l'atmosphère. Cette étude s'inscrit dans un projet plus global de développement des bétons de bâtiment à matrices binaires (ciment + additions) s'appuyant sur des critères de propriétés de transfert. En effet, afin de répondre à certaines exigences de durabilité, une campagne expérimentale a été menée sur des bétons confectionnés selon la norme européenne NF EN 206 qui autorise deux méthodes de formulation : * l'approche dite prescriptive, qui porte sur des obligations de moyens, * l'approche dite performantielle, qui consiste à fixer des exigences en terme de performances basées sur des indicateurs généraux ou spécifiques de durabilité. Ce travail de recherche a donc consisté à comparer les propriétés physico-chimiques de bétons à forte teneur en addition minérale (filler calcaire, cendre volante, laitier de haut fourneau et métakaolin), dérogeant à l'approche prescriptive avec celles des bétons de référence répondant à cette même norme. Cette comparaison s'est effectuée au travers d'indicateurs de durabilité généraux (porosité accessible à l'eau, perméabilité à l'oxygène, coefficient de migration des ions chlorure et teneur en Ca(OH)2) et d'indicateurs spécifiques : la résistance à la carbonatation naturelle et accélérée. D'un point de vue méthodologique, les travaux réalisés dans le cadre de cette recherche ont montré l'intérêt de l'approche performantielle pour la formulation des bétons. Mais, à l'heure actuelle, les outils disponibles, c'est à dire les indicateurs généraux et spécifiques, ne sont pas suffisants pour répondre à l'ensemble des bétons couvrant ce texte normatif. A l'échelle du matériau (béton pour une application en bâtiment), les campagnes expérimentales menées ont montré que dans la majorité des cas, les bétons à forte teneur en addition minérale (dérogeant aux spécifications) présentent des comportements proches de ceux observés sur les bétons de référence (répondant à l'approche prescriptive)<br>The manufacturing of cement, by its clinkering process, is very energy-consuming and emits an important quantity of greenhouse gases in the atmosphere (1 ton of clinker produced 1 ton of CO2 released into the atmosphere). To maximize this latter from an environmental point of view, it is necessary to reduce the cement content. This can be done by replacing part of the cement with mineral additives during the manufacturing phase. This substitution seems one of the most effective solutions allowing, at the same time, to decrease the energy consumed and to reduce the release of CO2 into the atmosphere. This study is part of a more comprehensive development project of concrete building binary matrices (cement + mineral additives) based on transfer properties criteria. Indeed, in order to answer certain sustainability requirements, an experimental campaign was conducted on concrete, made according to the new European standard (EN 206) that allows two methods of formulation: * a traditional prescriptive approach, based on limiting values for the composition (minimum binder content, maximum water to binder ratio, compressive strength class...) of concrete exposed to some aggressive environmental conditions, * an innovative method based on a performance approach for concrete properties. The present work aims at studying the physico-chemical properties of cementitious materials with high substitution rates of cement by mineral additions (limestone filler, fly ash, slag, metakaolin) derogating from the prescriptive approach with reference to concrete corresponding to the same standard. This comparison was made with general durability indicators (water porosity, oxygen permeability, chloride migration coefficient and portlandite content) and specific durability indicators: carbonation in natural and accelerated conditions. From a methodological point of view, the research carried out in the framework of this project has shown the interest of the performance-based approach with regards to the concrete formulation. But at the moment, the available tools, namely the general and specific indicators, are not sufficient to respond to all these types of concrete. However, considering the performance, economic and environmental criteria, laboratory results showed that concrete made according to a performance-based approach had a performance close to reference concrete and the standard prescription could still be reassessed
23
Silveira, Adriana Augustin. "Contribuição ao estudo do efeito da incorporação de cinza de casca de arroz em concretos submetidos à reação álcali-agregado." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2007. http://hdl.handle.net/10183/17556.
Full textAbstract:
A reação álcali-agregado no concreto é um fenômeno que tem como causa uma reação química que ocorre entre os hidróxidos alcalinos provenientes do cimento e alguns minerais reativos presentes no agregado. Esta reação pode causar a deterioração do concreto, pois os seus subprodutos podem tornar-se expansivos na presença de umidade, originando fissuração, diminuição da resistência, aumento da permeabilidade e, eventualmente, a ruptura da estrutura. O uso de adições minerais em concretos suscetíveis à reação álcali-agregado tem sido apontado como uma alternativa eficiente na prevenção da reação expansiva, juntamente com o uso de agregados não reativos e a limitação dos teores de álcalis no cimento ou concreto. Neste contexto, o presente trabalho teve como objetivo principal a investigação do processo de deterioração do concreto devido à reação álcali-sílica, principalmente no que se refere ao tipo ou mineralogia do agregado e à utilização de cinza de casca de arroz, como substituição parcial do cimento Portland. Desta forma, o programa de pesquisa compreendeu, a realização de ensaios de expansão acelerada em barras de argamassa (ASTM C1260/94) moldadas com cimento Portland tipo CP-I S 32, com teores de 12,5; 25 e 50% de dois tipos de cinza de casca de arroz, em substituição parcial ao cimento, e quatro diferentes tipos de agregados (basalto B, basalto BGO, granito e riodacito). A microestrutura dos materiais utilizados e das barras submetidas ao ensaio acelerado foi avaliada através de técnicas analíticas e experimentais, tais como, petrografia, difração de raios x, porosimetria por intrusão de mercúrio, microscopia eletrônica de varredura e de transmissão (MEV e MET), com microanálise por detecção de energia dispersiva (EDS). Os resultados obtidos no ensaio acelerado comprovaram a potencialidade reativa das rochas analisadas e identificaram uma correlação entre o tipo de rocha e o teor de cinza de casca de arroz. A análise da microestrutura indicou que existe uma reação química da CCA com o meio alcalino utilizado no ensaio que acaba interferindo na formação e na relação C/S dos produtos expansivos resultantes da reação álcali-sílica.<br>The alkali-aggregate reaction in concretes is a phenomenon caused by a chemical reaction that occurs between alkaline hydroxides from Portland cement and some reactive minerals from aggregates. Such reaction can cause severe concrete deterioration, as its by-products can become expansive in the presence of water, originating fissuration, strength reduction, permeability increase, and eventually, the failure of concrete structures. The use of mineral admixtures in concretes susceptible to the alkali-aggregate reaction has been pointed out as an efficient alternative to prevent concrete expansion, along with the use of non-reactive aggregates and the limitation of the alkali amount in cement or concrete composition. In this context, the main purpose of the present work was the investigation of concrete deterioration due to the alkali-silica reaction, focusing the aspects related to the type or mineralogy of the aggregate and the utilization of rice husk ash as partial substitution of Portland cement. The research program comprised initially accelerated expansion tests carried out in mortar bars (ASTM C 1260/94), which were molded using CP-I S 32 Portland cement, 12.5, 25, and 50% contents of two types of rice husk ash, as partial replacement to the cement, and four different types of rock aggregates (basalt B, Basalt BGO, granite, and rhyodacite). Also, the microstructure of the concrete mixtures investigated, after being submitted to expansion in the accelerated tests, were evaluated through experimental and analytical techniques such as petrography, mercury intrusion porosimetry, x-ray diffraction, scanning and transmission electron microscopy (SEM and TEM), and energy dispersive detection (EDS). The results obtained have proved the reactivity potential of the investigated rock aggregates and identified a correlation between type of aggregate and rice husk ash content. The microstructure analysis indicated that the occurrence of a chemical reaction involving the rice husk ash in the alkaline environment established in the tests, had a significant effect on the amount of expansive by-products as C/S relation resulting from alkali-silica reactions.
24
Křížová, Klára. "Studium závislostí složení betonů na hodnoty modulů pružnosti." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-233789.
Full textAbstract:
The modulus of elasticity is one of the basic characteristics of concrete defining elastic deformation of concrete and it plays a significant role in the static design of structures. Due to current trends in concrete technology, offering a wide variability in the proposals of the composition of concrete, there are changes not only in strength characteristics but also in the modulus of elasticity of concrete. The aim of this doctoral thesis is to study the dependence of different compositions on modulus of elasticity of concrete. Design of concrete composition is prepared with respect to the use of different types of cement, mineral admixtures, types and fractions of aggregates. The work is mainly focused on the determination of static modulus of elasticity in compression with the addition of dynamic modules. In the first phase determined modulus of elasticity are compared with tabulated values according to Eurocode 2, which are derived for the specific strength class of concrete. Part of this work is the compilation of the main technological aspects of concrete which can favorably affect the modulus of elasticity.
25
Bílek, Vlastimil. "Možnosti využití odpadních písků z výroby vodního skla ve stavebnictví." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2013. http://www.nusl.cz/ntk/nusl-216992.
Full textAbstract:
Nowadays, the waste sands from the water glass production have no utilization and due to high alkali content are considered as a dangerous waste. So the aim of this thesis is to find and study some possibilities of their utilization in the building industry. First of all, some necessary analysis of these sands were performed and then some advantages and disadvantages of their application for production of materials based on portland cement and alkali activated materials were studied. Characteristics of fresh and hardened pastes, mortars and concretes containing these waste sands were determined. The most tested properties were their workability and their compressive and flexural strength. Close attention for the risks of alkali-silica reaction and for options of its suppressing by the mineral admixtures was paid.
26
Cheng, Ming-Yao, and 鄭名堯. "The Effect of the Mineral Admixture on Permeability Properties of Concrete." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/88695045609554839961.
Full textAbstract:
碩士<br>東南技術學院<br>防災科技研究所<br>94<br>The purpose of this study is to evaluate the effect of mineral admixtures on mechanical properties and permeability of concrete. Mineral admixtures were used in the various mixes to replace the concrete usage and control the environment factors (high temperature, loading) and water binder ratio. The test results show that concrete with adding anti – permeation in high temperature will advance the permeability; the permeability of concrete will be advanced along with the load increment. The permeability advancement is happened also in anti – permeation paste. Besides the anti – permeation concrete also plays a big role in impermeability effect, the optimum adjunction is 6%. In addition, both of the electrical resistance value and Ultrasonic Pulse Velocity become higher.
27
Nai-Min, Huang, and 黃乃明. "Effect of Mineral Admixture on the Properities of High Performance Concrete." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/04530110170556743000.
Full textAbstract:
碩士<br>國立臺北科技大學<br>土木與防災技術研究所<br>92<br>This paper is to study the effect of the workability of high performance concrete with aggregate and mineral admixture. Test variables include the sand over aggregate and the mineral admixture replacement. The slump test, slump flow test, and passing height from U test were performed to correlate the effect of the workability, and test for compressive strength and elastic modulus. The testing results indicate that the compressive strength and elastic modulus are not significantly affected by sand ratio computed from a constant aggregate volume, but are influenced by the elastic properties of the paste. The workability test results indicate that can increase of sand ratio can improve workabi1ity of HPC. Slag is better than fly ash in HPC mixture as far as workability is concerned.
28
蔡宜珍. "Study on permeability of concrete with mineral admixture using gas permeability method." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/70130133011936322983.
Full textAbstract:
碩士<br>國立臺灣科技大學<br>營建工程系<br>91<br>By using the properties of low burning temperature and easy vaporization for methanol liquid, this research conducted various gas permeability experiments on concrete specimens. First of all, the mechanism of gas permeability method was established. Then, different variables such as the thickness of specimen, water to binder ratio (W/B), addition of Pozzolanic materials and compressive strength of cylinderical specimen, etc. were used in the gas permeability experiments to study the feasibility for assessing the durability of concrete.
Experimental results show that the thickness of the specimens used in the methanol permeability test has better be bigger than the maximum size of aggregate; the permeability of concrete with high W/B is greater than that with low W/B. Taking the concrete with slag as an example, the concrete specimen with W/B of 0.65 and thickness of 20 mm at age of 365 days has a coefficient of permeability of 3.596E-17m2, that is higher than 2.911E-17 m2 for a concrete specimen with W/B of 0.5. Adding Pozzolanic material into concrete reduces its permeability. The permeability coefficient of pure concrete is the biggest, concrete with slag is smaller, and concrete with fly ash is the smallest. Taking concrete specimen with W/B of 0.55 and thickness of 10 mm as an example, at age of 365 days, the coefficient of permeability is 2.038E-17 m2 for F55 concrete specimen (adding fly ash), 2.208E-17 m2 for S55 concrete specimen (adding slag) and 7.730E-17 m2 for C55 pure concrete specimen. The sequential relationship of the coefficient of permeability for these three kinds of concrete matches those results in previously published papers. The coefficients of permeability of concrete will decrease with the increase of its compressive strengths or the addition of pozzolanic materials. The order of the reducing rate of coefficient of permeability for concrete specimens is F65 concrete with fly ash (smallest), S65 concrete with slag, and C65 pure concrete (biggest).
29
Liao, Chan-Chang, and 廖展章. "Assessment Concrete Durability For Different Mineral Admixture Contant By Using Acceleration Chloride Migration Test." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/33904769293923418047.
Full textAbstract:
碩士<br>國立臺灣海洋大學<br>材料工程研究所<br>92<br>The accelerated chloride migration test (ACMT) was used to investigate the effect of mineral admixtures on the resistance of chloride ion penetration in concrete. Testing variables include the content of fly ash/ground granulated blast-furnace slag and water/binder ratio. Cylindrical specimens with a dimension of 10x20cm were cast for compressive strength test and chloride penetration test. Chloride ion flux and the chloride ion migration coefficient were evaluated using the test data and Nernst-Planck equation.
It was found that partial replacement of fly ash/slag for Portland cement in concrete is beneficial for resistance of chloride ion penetration. The optimum percent of replacement is 25% for fly ash and 45% for slag, respectively. Slag replacement is better than fly ash replacement as far as migration coefficient is concerned. And, there is no definite relationship between compressive strength and flux (or chloride migration coefficient).
30
Ou, Sue-Hao, and 歐書豪. "Effects of Mineral Admixture and Steam Curing on the Thermal Conductivity of Mortar with Various Compositions." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/16370661525244943704.
Full textAbstract:
碩士<br>國立臺灣科技大學<br>營建工程系<br>91<br>This research used the Hot Wire Method by inserting a thermal needle probe in a drilled hole to study the effects of mineral admixture and steam curing on the thermal conductivity of mortar with various compositions. The effect of moisture content of fine aggregate on its thermal conductivity was studied first. Subsequently, under a constant water-to-cement ratio (w/c = 0.42), various sets of mortar were made with different sand-to-cement ratios by weight (s/c = 0.75, 1.75 and 2.75); and then under a constant sand-to-cement ratio (s/c = 1.75), mortars with two types of water-to-cement ratio (w/c = 0.34 and 0.5) were also produced. To study the effects of pozzolanic materials, mortars with 20% and 40% by weight of cement replaced by fly ash and slug, respectively, were fabricated. Finally, a steam curing of 50℃ and 70℃ for pure mortars and mortars with 20% and 40% by weight of cement replaced by fly ash and slug , respectively, were also conducted to study its effects on the thermal conductivity of mortar.
Experimental results show that: (1) the higher the moisture content of fine aggregate is, the higher its thermal conductivity will be; (2) the mortar with a higher content of fine aggregate does not necessarily yield a higher thermal conductivity mortar. The mortar with higher content of fine aggregate reduces its amount of cement past and consequently lowers its thermal conductivity; (3) the mortar with a lower water-to-cement ratio has a higher thermal conductivity than that with a higher water-to-cement ratio, e.g., the thermal conductivity of mortar with a water-to-cement ratio of 0.34 was 2.079 W/m℃, about 31.22% higher than 1.5840 W/m℃for a mortar with a water-to-cement ratio of 0.5; (4) adding fly ash or slug into mortar will increase the thermal conductivity at age of 28 days; however, the quantity must be adequate, e.g., the test results indicate that a 20% replacement is more favorable than 40%; (5) high temperature increases the speed of hydration, but decreases the thermal conductivity of mortar also at age of 28 days. Adding fly ash or slug into mortar helps minimize the porosity and crack causing by high hydration rate and high temperature. For such case, the thermal conductivity will increase as well.
31
Chen, Po-Yu, and 陳柏佑. "The Study on the Mechanical Properties of Waste Oyster Shells with Mineral Admixture used in Cement Mortar." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/00877629313672209121.
Full textAbstract:
碩士<br>國立高雄應用科技大學<br>土木工程與防災科技研究所<br>99<br>The oyster shell is the by-product from the shellfish farming. Most of them are disposed to landfill without preprocessing and caused the serious environmental problems. In this study, the recycled oyster shell sand is used to replace fine aggregate. The water-to-cement ratio (W/C) of all mixture proportions was controlled at 0.485. Some of mortar specimens were mixed by using four replacements of 0%, 5%, 10% and 15% with recycled oyster shell sand, respectively. The others were mixed by using five replacements of 0, 5, 10, 20 and 30% by weight with the mixture of ratio 1:1 oyster shells and slag or fly ash, respectively. The fresh, harden and durability properties of mortar were tested. Finally, the feasibility of application for engineering was also evaluated.
The experiment result shows that the reduction of fluidity ratio is range of 3.1-9.5% due to increase oyster-shell replacement. By comparing to control group, the initial and final setting time of mortar with oyster-shell replacement decreased 13-53 minutes and 75-125 minutes, respectively. The compressive, flexile and tensile strength of specimens at 28 days age was about 85, 81 and 80% compared to control group, respectively. The increasing of absorption is range of 6-11% and the volume changed is about 0.072%. Both results were higher than the controlled group. The chloride ion content of mixtures is range of 0.081-0.139 kg/m3 and meets the standard. The sulfate resistance ability of mixtures decreased since the oyster shell has a large amount of pores and its higher absorption.
On the other hands, the result of mortar consists of oyster shells and mineral admixture, show that the increasing of fluidity ratio is range of 2.1-4.3%. For the mixture with the replacement of oyster shell and slag, the increasing of initial and final setting time was range of 28-95 minutes and 96-235 minutes, respectively. For the mixture with the replacement of oyster shell and fly ash, the increasing of initial and final setting time was range of 18-83 minutes and 70-180 minutes, respectively. The compressive strength in early age is similar to the control group. Comparing to the control group, the increasing of compressive strength is range of 2-22%and the decrease of absorption is range of 1.4-6.5% after 56 days age. The volume change
ratio is above 0.055% and it is lower than the control group. The chloride ion content of mixtures is range of 0.056~0.146 kg/m3 and also meets the standard. The ability of sulfate resistance was increasing since the pozzolanic effect is occurred from slag or fly ash and the hydration product filled the pores of mortar.
The engineering properties of mortar consists the proper amount of oyster shells are similar as cement mortar. According to the concept of the sustainable development and the green building material, the oyster shell waste can be recycling used after appropriate processing. The feasibility of application for engineering was successful by concerning of source, engineering properties, technology, and economic. According to this study, a solution for reduce and recycling used the waste was provide and improve the sustainable development. It also contributes to the program for environmental action and the sustainable development of the Earth is also helpful.
32
Lin, Chien-Liang, and 林建良. "The Influence of Mineral Admixture and Size Gradation of Aggregate on the Properties of Fresh Self-Compacting Concretev." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/66098341793811883318.
Full textAbstract:
碩士<br>國立臺灣科技大學<br>營建工程系<br>88<br>The Influence of Mineral Admixture and Size Gradation of Aggregate on the Properties of Fresh Self-Compacting Concrete
Thesis Advisor : Ta-Peng Chang
Graduate Student : Chien-Liang Lin
ABSTRACT
The research uses computer program to do mixture proportioning design of self-compacting concrete (SCC). It has two principal research categories. One is to study the influence of eight kinds of weight ratio of fly ash to the slag powder on the properties of fresh self-compacting concrete under the fixed 0.35 m3 volume of paste and 0.155 m3 volume of powder. The other, under three kinds of the fixed volume of paste and powder, is to study the influence of four kinds of weight ratio of fly ash to the slag powder incorporating with three kinds of size gradation of coarse aggregate on the properties of fresh and hardened self-compacting concrete.
Research results show: (1）When the MSA (Max. size aggregate) bigger than 20 mm, the flowing property of concrete passing through a vacant space between the reinforcement will be relatively poor. Therefore, it is better to use MSA smaller than 20 mm in making the mixture proportioning design of SCC; (2) Among all the mixture proportioning designs of SCC used in the research under the condition of having more amount of coarse aggregate (Vg = 0.33 m3), the proportion with the weight ratio of fly ash to the slag powder of 6:4 has the best filling capacity; (3) Under different size gradations of coarse aggregate, the weight ratios of fly ash to slag powder of either 2:8 or 8:2, it will be much easier of make a better SCC; (4) The second size gradation of coarse aggregate (mixture of the 3/4” sieve and 3/8” sieve) can incorporate with more kinds of binding material having different weight ratios of fly ash to slag powder to successfully make the SCC; (5) At the age of 56days, the engineering property of hardened concrete with more slag powder presents a better developing rate of strength, elastic modulus, pulse speed, and electrical resistance, etc., than the concrete with more fly ash.
33
Jang, Se Hoon. "Identification of Concrete Incompatibilities Using Cement Paste Rheology." 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-05-349.
Full textAbstract:
The complex interaction between cement and chemical/mineral admixtures in concrete mixtures sometimes leads to unpredictable concrete performance in the field which is generally defined as concrete incompatibilities. Cement paste rheology measurements instead of traditional workability tests (i.e., slump cone test) can have great potential in detecting those incompatibilities in concrete before the concrete is placed, which can, in turn, avoid related workability problems and setting time as well as heat evolution abnormalities. The objectives of the present study were to examine the applicability of the dynamic shear rheometer (DSR) to measure cement paste rheology, and to identify cement and mineral/chemical admixture incompatibilities, based on the determined rheological parameters.
The DSR was modified and optimized for cement paste rheology measurements. Two different modes of operations (i.e., static and dynamic methods) with the modified DSR were investigated to measure representative rheological parameters as well as to identify cement and chemical/mineral admixture incompatibility. The conventional plastic viscosity and yield stress are measured in static mode and storage modulus curve, as a function of time, is measured in dynamic mode. The rate of change of plastic viscosity (RPV) as another static rheological parameter and the modeled magnitude parameter ?, from the dynamic rheological method, showed great potentialities as acceptance criteria to identify incompatible mixtures. The heat of hydration data from isothermal conduction calorimeter tests and setting time results for the studied mixtures have strongly supported the rheology based observations as supporting tools. Based on the main tests results, the acceptance criteria were set up using the rheological parameters in accordance with heat of hydration data. This will ultimately help material suppliers, concrete producers, and other users to detect problematic combinations of concrete ingredients before a given concrete mixture is placed.
34
Santos, Bruno Luís Correia. "Eficiência de misturas ternárias : aplicação do conceito do fator-k." Master's thesis, 2012. http://hdl.handle.net/1822/29608.
Full textAbstract:
Dissertação de mestrado integrado em Engenharia Civil<br>A indústria de produção de cimento é atualmente uma das indústrias mais poluentes,
contribuindo negativamente e de forma considerável na emissão de gases tóxicos para
atmosfera. Existe, portanto, uma necessidade geral de redução da dependência e utilização do
cimento a fim de minorar os seus efeitos no ambiente. Uma forma de diminuir a sua
necessidade, é a sua substituição parcial por adições minerais.
Neste sentido, o estudo realizado incide sobre um conceito de eficiência na
substituição do cimento por adições minerais no fabrico de argamassas. Este conceito,
designado por fator de eficiência k, visa, através de uma relação com características de uma
argamassa padrão, obter um valor para a eficiência da aplicação de uma determinada
quantidade de adição mineral na composição de uma mistura de matriz cimentícia. Os
materiais minerais incorporados alvo de estudo foram as cinzas volantes (CV) e o metacaulino
(MTK). O estudo compreende no total, o fabrico e ensaio de 600 provetes constituídos por
argamassas padrão; 20%, 40% e 60% de substituição de cimento por CV; 10%, 20% e 30% de
substituição de cimento por MTK e argamassas de 10%CV+10%MTK, 30%CV+10%MTK e
50%CV+10%MTK, produzidas com razões de água/ligante de 0,35, 0,4, 0,5, 0,6 e 0,7. Foram
realizados ensaios de espalhamento e de compressão no decorrer da determinação do fator k.
O fator k é analisado segundo a idade, percentagem de substituição e nível de tensão nas
idades de 7, 28, 90 e 180 dias. O presente estudo é igualmente elaborado de forma a estudar o
comportamento do fator k em composições não previstas na norma NP EN 206-1. Verificouse
que a resistência à compressão aumenta com a idade assim como o fator k de modo geral é
maior comparando o seu valor na idade inicial e final permitindo concluir o benefício da
incorporação de adições minerais em argamassas. Foram obtidos valores de eficiência, em
média, de 0,8, 0,9 e 1 nas argamassas com 20%CV, 40%CV e 60%CV, respetivamente. Nas
argamassas 10%, 20% e 30%MTK os valores situaram-se em 0,6, 1,2 e 1, respetivamente. As
adições conjuntas de CV e MTK obtiveram valores de k médios de 1,2, 1 e 1,4 para
10%CV+10%MTK, 30%CV+10%MTK e 50%CV+10%MTK, respetivamente.<br>Cement production is currently among the most polluting industries, significantly
contributing to the emission of toxic gases into the atmosphere. The global need to reduce the
dependence on using cement, in order to minimize environmental impact, is therefore widely
recognized. One of the means of reducing the need for cement is to partially replace it with
mineral admixtures.
In light of this, the study approaches a concept on the efficiency of substituting cement
with mineral admixtures when making mortar. This efficiency concept, called k-value, aims to
obtain - based on the ratio of features on a standard mortar reference - a specific efficient
quantity for the mineral admixture when mixing mortars with equivalent characteristics. The
mineral admixtures studied are fly ash (CV) and metakaolin (MTK). The study in total
included the manufacturing and tests of 600 test cubes consisting of mortars: standard, 20%,
40% and 60% of substituting of cement with fly ash, 10%, 20% and 30% of substituting of
cement with metakaolin; and mortars with 10% fly ash + 10% metakaolin, 30% fly ash + 10%
metakaolin and 50% fly ash + 10% metakaolin produced with binder/water ratios of 0,35, 0,4,
0,5, 0,6 and 0,7. In the process of determining the k- value, slump flow and compressive
strength tests are carried out. The k-value was analyzed by specimens’ age, replacement
percentage and tension level for ages of 7, 28, 90 and 180 days. The study also aims to
analyze k-value behavior on composites that are not covered by the NP EN 206-1 Standard. It
was found that the compressive strength increases with age and also in general the k value
comparing its initial and final age value allowing to confirm the benefits of mineral admixture
in mortars. Efficiency values were obtained on average of 0,8, 0,9 and 1 in mortar with
20%CV, 40CV and 60%CV, respectively. In mortars with MTK in 10%, 20% and 30% values
were 0,6, 1,2 and 1, respectively. The mixtures with CV and MTK obtained k values in a
average of 1,2, 1 and 1,4 for 10%CV+10%MTK, 30CV+10%MTK, 50%CV+10%MTK,
respectively.
35
Lin, Li-Chen, and 林立晨. "The Research on Self-Curing Admixtures with Mineral Admixtures-Mortar and Concrete." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/brbkd4.
Full textAbstract:
碩士<br>國立交通大學<br>土木工程系所<br>102<br>The purpose of curing is to prevent excessive evaporation of water from the concrete to achieve full hydration to improve quality of the concrete. With today’s environmental consciousness of human being, the progress of material technology and economic needs, the use of mineral admixtures (slag, fly ash) often replace part of cement, but pozzolanic reaction of mineral admixture is later than the hydration reaction of cement. This makes curing more important to guarantee the effectiveness of pozzolans.
This study use different pozzolan replacements with the addition of SCA to test the fresh and hardened concrete’s properties and to achieve more energy-efficient concrete. The experiment was divided into two phases. The first used w/b 0.38 of mineral admixtures-cement mortar in different proportions with SCA, and after curing, the weight loss, compressive strength and shrinkage were tested to investigate the best combinations of replacement ratio and SCA. The second phase was to select the mix proportion which show better performances and then use them in producing concrete and test the workabilty, mechanical properties, volume stability and durability. Several curing regimes were employed for comparison. And multi-variable regression analysis was executed.
The results show that the optimum replacement ratio for slag is 30-50% and fly ash is 0-10% of total cementitious material in mineral admixtures-cement mortar. The 3 day wet curing specimens with SCA (C5S5 and C7S3) are very close or even better than standard cured specimens without SCA in mechanical properties and durability. The 3 day strength with SCA has exceeded the design strength and reaches 280 kgf/cm2, and the specimens with SCA at 90 days, the resistance to chloride ion penetration (RCPT) and resistivity are better than the specimen without SCA. Proportions use 3 day wet curing with SCA can reach the performances of standard cured specimens without SCA.
36
Hsu, Jui-Lin, and 許瑞麟. "The Influence of Added Mineral Admixtures on Self-compacting Concrete." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/58835489667194440205.
Full textAbstract:
碩士<br>國立屏東科技大學<br>土木工程系碩士班<br>91<br>The influences of added mineral admixtures on the engineering properties of self-compacting concrete for early performance and the strength at latter stages are presented in this research 。The aim is to substitute pure cement with different proportion of the compound admixtures as well as to ensure the early and later performance。The amount of powder、water-cementitious rations、high performance water reducing admixtures、cement and aggregates are taken as fixed quantities。While the amount of cement is replaced by different compound admixtures ratios of slag powder 、fly ash、lime stone powder。
The experimental results of this research are summarized as below：(1)The use of compound admixtures of Slag and fly ash 50:50 to 0:100 in place of the amount of cement can lead too better performance in early stages。 (2) The use of added slag powder in place of pure cement can lead to similar performance in early stages。 (3) The added Lime stone powder is a great benefit to flowability ,but don’t contribute performance the development of strength。(4) Adding fly ash has great benefit to the performance of latter stages than adding slag powder，the adding pozzolanic materials for the splitting strength and compressive strength is not suitable for traditional concrete。(5) Added slag powder of this study shows that the elastic modulus of concrete is approached to the value of pure cement，and static-dynamic elastic modulus is lower to added Lime stone powder。
37
Hsing, Chang Yung, and 張永興. "A study on the properties of lightweight concrete with mineral admixtures." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/43510411356109880193.
Full textAbstract:
碩士<br>國立高雄應用科技大學<br>土木工程與防災科技研究所<br>95<br>The global warming has been happening for these years. It has been attached great importance for decreasing energy consumption, which be used by air conditioning in buildings to transform the temperature. The conclusion that above mentioned is improving the duty of air conditioning and heat insulation of building. In this study, the lightweight aggregate concrete with w/b ratio of 0.40 was produced. Four mineral admixtures are fly ash, blast furnace slag, desulphurization dreg and glass powder, which individually replaces cement by 10% and 30% of weight, through the thermal conductivity test to investigate the heat insulation, proceed to the experiments of harden, non-destructive and durability properties on 7, 28, 56, 91 and 120 day in curing ages, and analyses the economic benefits in lightweight concrete with each mineral admixtures.
The study results show : The slump of mixtures would be increased and decreased with the kind different of mineral admixtures. GLP10 has the highest compressive strength which be higher than MA0 about 6.26% and 13.45% on 28 day and 120 day. In addition, the development of compressive strength would be differentia with different mineral admixtures. Each mixture is shown expanded and higher than MA0 about 133%~267%. Ultrasonic pulse velocity are higher than MA0 about 98%~105% on 120 day, because of the replacement and properties of mineral admixtures. Electric resistivity is seriously affected by chemical properties of mineral admixtures. FA30 and GLP30 are respectively higher about 455% and 377%. (2) The thermal conductivity (K) of lightweight concrete with mineral admixtures has excellent effect in heat insulation which could be reduce about 0.41%~25.71%. It is caused by the changes of unit weight and water absorption ratio. In addition, the contents of chemical elements and hydration products also cause the consequences. Mineral admixtures could increase the economy for concrete, and in these mixtures, FA30 has the best heat insulation, GLP10 is secondary but it’s better for compressive strength of concrete in early and late ages.
38
Wu, Tehsien, and 吳德憲. "Properties of Cement-based Composites Using Steel Fibers and Mineral Admixtures." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/05107039257385434899.
Full textAbstract:
博士<br>國立臺灣海洋大學<br>材料工程研究所<br>103<br>Traditional concrete is a poor electrical conductor, especially under dry conditions. However, conductive concrete can attain relatively high conductivity by adding a certain amount of electronically conductive components like steelfibers orgraphiteconductivematerial in the regular concrete matrix. The potential applications of conductive concrete include anti-static flooring, electromagnetic shielding, cathodic protection of reinforcing steel in concrete structures, and roadway deicing.In addition, reduction of Portland cement in traditional concrete has been an interesting and important topic motivated by the environmental, economic and technical requirements. Thus, this study includes two parts. The first part of this study is to investigate the electrical and thermal propertiesof conductive concrete with various graphite contents, specimen dimensions and applied voltages. The second part is to investigate the characteristics of circulating fluidized bed combustion (CFBC) fly ash and the properties of cement-based composites with various combinations of CFBC fly ash and coal-fired fly ash.
For the first part, six different mixtures (control mixture and five conductive mixtures with steel fibers of 2% by weight of coarse aggregate and graphite as fine aggregate replacement at the levels of 0%, 5%, 10%, 15% and 20% by weight) were prepared and concrete blocks with two types of dimensions were fabricated. Four test voltage levels, 48V, 60V, 110V, and 220V, were applied for the electrical and thermal tests. Test results show that the compressive strength of specimens decreasesas the amount of graphite increases in concrete. The applied voltage decreases electrical resistivity and increases temperature of concrete. Meanwhile, higher electrical current and temperature have been obtained in small size specimens than the comparable large size specimens. The superior electrical and thermal properties have been obtained in the mixture adding 2% steel fibers and 20% graphite.
For the second part, the physical-chemical cementitious characteristics of CFBC fly ash and the properties of cement-based composites with various combinations of CFBC fly ash and coal-fired fly ash are investigated. The liquid/binder ratio was kept at a constant of 0.5. Thirteen different blended cements were prepared with varying proportions of ordinary Portland cement, coal-fired fly ash, and CFBC fly ash. The selected replacement levels of coal-fired fly ash and CFBC fly ash were 30%, 40%, 50%, 60%, and 70% and 20%, 30%, and 40% by weight of OPC, respectively. Test results shows that the CFBC fly ash cannot meet the chemical and physical requirements in ASTM C821-09 (Standard specification for lime for use with pozzolans), but is consistent with the requirements of ASTM C593-06 ( Specification for fly ash and other pozzolans for use with lime for soil stabilization ). It indicates that CFBC fly ash has the potential instead of cementitious materials and as an alternative of pozzolan. The initial setting time increases with an increasing amount of cement replacement by CFBC fly ash and coal-fire fly ash. The lower compressive strength has been obtained in mortar with various combinations of coal-fired fly ash and CFBC fly ash than the comparable ordinary Portland cement mortar. Coal-fired fly ash can be effectively used in reducing length change. However, CFBC fly ash would results in a higher length change when adding over 30%. Thus, the amount of CFBC fly ash replacementcement was recommended to be limited below 20%.
39
Wang, Yu-Chen, and 汪侑榛. "The research on the combination of various mineral admixtures to produce underwater self-compacting concrete." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/82817295055324139123.
Full textAbstract:
碩士<br>國立交通大學<br>土木工程系所<br>102<br>This study is to improve the durability, volume stability of underwater self-compacting concrete with various underwater anti-segregation admixtures developed by Dr. Wen-Chen Jau. Pozzolans are used with different percentage for comparison. The workability, passing ability, slump-flow, and V-funnel tests were performed to determine the self-compacting ability of the concrete. After the concrete hardened, the specimens were kept in different RH(40, 80%, and 100%) to determine the mechanical properties, volume stabilities, and durability. It is found that different anti-segregation admixtures exhibit different performs in terms of anti-washout, RCPT, and electrical resistance. In addition, it is also found that steel rebar can effective restrain the shrinkage, and better for higher steel ratio.
40
Huang, Wei-Chih, and 黃韋智. "The Study of Chloride Transport Behavior of Mortar with Mineral Admixtures by using Accelerated Chloride Migration Test." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/02891463578485364465.
Full textAbstract:
碩士<br>國立臺灣海洋大學<br>材料工程研究所<br>100<br>In this study, in order to investigate the chloride ions transport behavior in mortar, specimens (w/b= 0.45 and 0.55) was designed with variety volume fraction of fine aggregate (0%, 10%, 20%, 30%, 40% and 50%) and three types of mineral admixtures (20% fly ash, 45% slag and 10% silica fume of cement content), respectively. Fly ash group was cured in water for 91 days, others were cured for 28 days.
Test with compressive strength, accelerated chloride migration test (ACMT) and rapid chloride permeability test (RCPT).
For compressive strength, specimens with furnace slag or silica fume were higher compressive strength than control group. But, specimens with fly ash were lower compressive strength than the control group.
From experimental data of ACMT, when volume fraction of fine aggregate was 50%, the non-steady-state and steady-state of chloride migration coefficient would be speeded up suddenly. From experimental data of RCPT, the highest penetration is furnace slag group, and the fly ash group was the lowest. Comparison with ACMT, The RCPT test results was underestimated the penetrating of fly ash group, but overestimation the penetrating of furnace slag group.
41
Campos, Pedro Gabriel da Silva. "Betões eco-eficientes com elevados teores de adições minerais." Master's thesis, 2012. http://hdl.handle.net/1822/30313.
Full textAbstract:
Dissertação de mestrado integrado em Engenharia Civil<br>É do conhecimento geral que cada tonelada de cimento produzida é responsável pela emissão
de uma tonelada de CO2 para a atmosfera e, considerando o gigantesco volume de cimento
produzido mundialmente, qualquer redução significativa na sua produção e consumo, trará
vantagens ecológicas significativas.
De modo a contribuir para sustentabilidade da construção, a presente dissertação pretende dar
um contributo para a redução do consumo de cimento, através da sua racionalização,
substituindo elevados volumes de cimento no fabrico de betões por adições, nomeadamente
subprodutos industriais, tais como as cinzas volantes. Contudo, betões com elevados volumes
de cinzas volantes possuem alguns inconvenientes, os quais têm impedido a sua
generalização, pelo que se tentou mitigar tais inconvenientes, através da incorporação de
outras adições minerais (metacaulino e cal hidratada), que possam corrigir os principais
inconvenientes associados a este tipo de betões. Ainda relacionado com a eco-eficiência deste
material, procurou-se produzir um betão auto-compactável, evitando assim a necessidade de
vibração e consequente poluição sonora, para além, de se evitar decréscimos na durabilidade
das estruturas resultantes de uma deficiente compactação do betão.
Para tal, desenvolveu-se um programa experimental capaz de caracterizar o desempenho, face
à resistência e durabilidade, de misturas binárias, ternárias e quaternárias, produzidas com
elevados volumes de cinzas volantes e pequenas percentagens de metacaulino e cal hidratada.
Da análise dos resultados obtidos é possível evidenciar que a sinergia resultante destas
misturas revelou desempenhos promissores, concluindo-se que é possível produzir betões
auto-compactáveis com elevados volumes de cinzas volantes e, pequenas percentagens de
metacaulino e cal hidratada, com desempenhos mecânicos e de durabilidade adequados à
maioria das infra-estruturas correntes, a um custo bem mais reduzido que o preconizado
actualmente pelo betão corrente, podendo-se traduzir numa solução viável para a obtenção de
um betão eco-eficiente.<br>It is common knowledge that every ton of cement produced is responsible for emitting a ton
of CO2 into the atmosphere and considering the huge amount of cement produced worldwide,
any significant reduction in its production and consumption, will bring significant
environmental benefits.
In order to contribute to sustainable construction, the present paper aims to contribute to the
reduction in cement consumption through its rationalization, replacing large volumes of
cement by additions, including industrial byproducts such as fly ashes. However, concrete
with high volumes of fly ashes have some drawbacks which have prevented its widespread
and it is attempted to mitigate these drawback by incorporating other mineral additions
(metakaolin and hydrated lime) which can fix the main drawback associated to this type of
concrete. Also related to the eco-efficiency of this material, we sought to produce a
self-compacting concrete, avoiding the need for vibration and subsequent noise, as well,
preventing a decrease in durability of the structures as a result of a poor compaction of the
concrete.
To this end, it was developed an experimental program able to characterize the performance,
concerning to the strength and durability of binary, ternary and quaternary mixtures, with high
volumes of fly ash and small percentages of metakaolin and hydrated lime. After the analysis
of the results, the synergy resulting from the mixtures showed promising performances,
concluding that it is possible to produce self-compacting concretes with high volumes fly ash
and small percentages of metakaolin and hydrated lime, with mechanical and durability
performances suitable for the most current infrastructure at a much lower cost than the
traditional concrete, which could represent a viable solution to obtain an eco-efficient
concrete.