Dissertationen zum Thema „Recycled concrete fines“

La consommation de béton devient de plus en plus importante en raison d'une urbanisation accrue nécessitant la réhabilitation et la construction de bâtiments et d'infrastructures. Néanmoins, la production de béton qui doit accompagner le développement urbain entraîne des problèmes environnementaux relatifs à la préservation des ressources naturelles qui ne sont pas inépuisables. Malgré des efforts de recyclage, la plupart des matériaux recyclés sont généralement utilisés pour les travaux routiers ou de remblai. En s'inscrivant dans le Projet National Recybéton (PN), ce travail de thèse a pour objectif d'apprécier la valorisation du recyclage des matériaux issus des bétons déconstruits en les intégrant dans de nouveaux bétons. Deux types de matériaux recyclés sont étudiés, les fines qui sont produites en quantités importantes lors de la phase de concassage du béton d'ouvrage démoli, et les granulats (sable et gravillon) qui sont pour la plus grande part issus des granulats naturels initiaux. Le présent travail a donc pour mission de quantifier des propriétés des matériaux cimentaires aux différents états lors de l'utilisation de : * granulats recyclés dans le squelette granulaire, * fines de sable broyé (SBC) et de fines de dépoussiérage (FBC) en tant qu'additions minérales. La première partie est dédiée à l'étude de l'influence de l'état hydrique des granulats recyclés (sable et gravillon) sur l'évolution de la rhéologie du béton dans le temps, et à l'étude de leur incidence sur la résistance à la compression à 28 jours. Les résultats obtenus dans la limite du contexte expérimental nous permettent de suggérer des recommandations sur l'état hydrique initial des recyclés et sur leur taux d'incorporation dans le mélange de béton. La deuxième partie présente l'évaluation de la faisabilité d'utiliser des sables de bétons concassés et des fines de bétons concassés (récupérées industriellement) comme addition minérale dans les matériaux cimentaires. A partir des résultats obtenus, il est possible d'apprécier dans quelle mesure ces fines sont compatibles avec les matrices cimentaires aux états frais, durcissant et durci. La troisième partie propose une piste pour limiter le problème de la Réaction Alcali-Granulat (RAG) dans le béton de granulats recyclés. La stratégie est basée sur deux volets. La première insiste à vérifier l'applicabilité du fascicule de documentation FD P18-464 lors de l'utilisation de granulats recyclés. Le deuxième examine l'intérêt de l'utilisation des additions minérales pour limiter, voire empêcher la RAG
The concrete consumption has been becoming more and more important due to the increase of urbanization requiring the rehabilitation and the construction of buildings and infrastructure. Nevertheless, the concrete production that accompanies the urban development leads to many environmental problems related to the preservation of natural resources which are not inexhaustible. Despite of recycling efforts, most of recycled materials are typically used for road works or embankment. By participating in the French National Project Recybéton, this thesis aims to assess the enhancement of recycling materials issued from deconstructed concretes by incorporating them in new concrete design. Two types of recycled materials will be studied, the powder produced in large quantities during the crushing phase of demolished concrete, and the aggregates (sand and gravel) whose the most part issued from the initial natural aggregates. Therefore, research study aims to quantify the properties of cementitious materials in various states by the use of: • recycled aggregates in the granular skeleton, grinded recycled concrete sand and powder of dust removal as supplementary cementing materials. The first part is dedicated to the study of the influence of moisture states of recycled aggregates (sand and gravel) on the concrete's rheology evolution in time and the study of their impact on 28 days compressive strength. The results obtained within the limit of experimental context will allow suggesting recommendations on the initial moisture state of recycled aggregates and their incorporation's rate in the concrete mix. The second part presents the evaluation of the feasibility of using grinded recycled concrete sand and crushed concrete powder (industrially recovered) as supplementary cementing materials. From the results, it will be possible to assess the extent that these fines are compatible with cement matrix in the fresh state, hardening state and hardened state. The third part proposes a way to limit the problem of Alkali-Aggregate Reaction (AAR) in recycled concrete. The strategy is based on two methods. The first insists to verify the applicability of the FD P18-464 documentation when using recycled aggregates. The second examines the interest in the use of mineral additives to limit or even prevent the AAR

Les granulats de béton recyclé (GBR) ne sont pas suffisamment utilisés dans le secteur de la construction, principalement en raison de leur grande capacité d’absorption d’eau. Ces matériaux sont en effet composés de granulats naturels concassés et de pâte de ciment durcie adhérente qui possède une forte porosité. La première partie de ce travail de recherche s’intéresse à la valorisation des GBR de dimensions inférieures à 4 mm (sables recyclés) dans une formulation de mortier. Les comportements à l’état frais et durci de mortiers fabriqués soit avec un sable recyclé soit avec un sable naturel modèle sont comparés. Le sable naturel modèle est conçu dans le but d’obtenir des caractéristiques physiques proches de celles du sable recyclé. Cette démarche permet de mettre en évidence l’influence de la substitution d’un sable naturel par un sable recyclé de caractéristiques voisines. La seconde partie de ce travail consiste à trouver une piste de valorisation pour les particules de GBR inférieures à 125 µm. L’objectif est ici d’utiliser la poudre issue du broyage de GBR comme addition minérale. Un travail de caractérisation de la poudre recyclée permet de mettre en évidence que la fine recyclée reste poreuse après broyage. Un modèle théorique et une méthodologie expérimentale permettant d’estimer cette porosité sont développés. Enfin, des mortiers fabriqués avec un filler calcaire et une fine recyclée sont comparés, les résultats montrent que la fine recyclée peut être utilisée comme addition minérale
Recycled concrete aggregates (RCA) are not enough used in the construction sector, mainly because of their high water absorption capacity. These fine particles are composed of crushed natural aggregate and adherent hardened cement paste. The first part of this work consists in valuing particles smaller than 4 mm of an RCA in a mortar composition. Thus, the fresh and hardened behavior of mortar performed with recycled fine aggregate and model natural aggregate have been compared. The natural model fine aggregate has been performed to have an equivalent physical characteristics with the recycled one. This approach helped to understand the hardened behavior of the mortar made with recycled fine aggregate. The second part of this work consists in finding a recovery track for particles smaller than 125 μm of RCA, the goal is to use them as mineral addition. A characterization work show that the recycled powder is porous, thus a theoretical model and an experimental methodology allowing to estimate this porosity are developed. Finally, a comparison between mortar made with a limestone powder, and a recycled powder are compared. The results show that the recycled powder can be used as mineral additive in mortar composition

La valorisation de déchets de démolition en tant que granulats à béton présente un double objectif de préservation des ressources naturelles et de désengorgement des sites de stockage. Les granulats recyclés de béton présentent la particularité de contenir du mortier résiduel qui influence certaines de leurs propriétés et, par voie de conséquence, celles des bétons dans lesquels ils sont utilisés. Cette thèse a pour but de développer l’utilisation de bétons de granulats recyclés en remplacement total des matériaux naturels. Elle a été réalisée en partenariat industriel avec l’entreprise CHRYSO.Une étude approfondie des propriétés des granulats recyclés de béton sur plusieurs lots (plateforme industrielle et laboratoire) a conduit à l’identification puis à l’analyse des spécificités de ces matériaux comparés aux matériaux naturels. La validité des protocoles expérimentaux a été testée, et de nouveaux protocoles ont été proposés axés sur ces spécificités. Les granulats recyclés présentent une absorption plus élevée, une résistance à l’abrasion plus faible, une distribution granulaire plus étalée et une circularité moindre que les granulats naturels. La granulométrie, la proportion d’éléments fins et l’absorption d’eau des sables recyclés sont des caractéristiques dépendantes d’une part, du prélèvement des granulats recyclés et d’autre part, de la robustesse des protocoles expérimentaux. Une réactivité des éléments fins a été démontrée pour les lots issus de laboratoire, mais son influence sur les propriétés des bétons peut être considérée de second ordre lorsque les éléments fins sont constitutifs du sable. Enfin, l’absorption et la morphologie des granulats recyclés sont dépendantes de la classe granulaire étudiée. Des corrélations entre les propriétés morphologiques/géométriques et l’absorption ont été démontrées. A l’issue de l’analyse de ces propriétés, des corrections ou adaptations aux modèles prévisionnels de performances ont été proposées. La faisabilité de réalisation de bétons de granulats recyclés de béton avec remplacement total des matériaux naturels (BGRB à 100%) a ensuite été démontrée. Pour de tels matériaux, la conservation des éléments fins inférieurs à 63μm est conseillée car nécessaire à l’obtention d’un squelette granulaire correct.Afin de compenser la perte d’ouvrabilité et de résistance mécanique observée avec l’utilisation des granulats recyclés de bétons, une recherche d’adjuvant a été menée et a conduit au choix de superplastifiants de la famille des polycarboxylates. Les interprétations proposées permettent de mieux comprendre la formulation des bétons de granulats recyclés de béton et des mortiers de bétons équivalents (MBE). Ainsi, la complexité des cinétiques d’absorption et de désorption d’eau conduit à une discussion autour de la notion d’eau efficace ; la différence de morphologie des granulats recyclés implique une correction du squelette granulaire ; enfin la fragilité des granulats recyclés à l’abrasion pose la question de sa prise en compte dans la détermination du squelette granulaire optimal.Enfin, une analyse comparative des impacts environnementaux des bétons de granulats recyclés de bétons ouvre des perspectives intéressantes
Promoting the use of demolition waste as recycled aggregates presents a double objective: first to preserve natural resources and secondly to relieve storage site. In regards to natural aggregates, recycled aggregates contain mortar that influences theirs properties and those of concrete in which they are used. The objective of this thesis is to develop the use of 100 % recycled aggregates in concrete. This study was realised in patnership with the company CHYRSO. Properties of recycled concrete aggregates collected from several sources were studied to identify and analyse their specificities ; results were compared to natural ones. Normalised methods were modified in order to be applied on recycled aggregates and new methods were also proposed. Recycled aggregates present higher water absorption, lower mechanical strength, spreader granular distribution and a less circular shape compared to natural aggregates. The granulometry of recycled sand, fines content and the water absorption are properties that depend on the sampling and the robustness of protocols used. A reactivity of fines obtained from materials made at the laboratory have been established, meanwhile their influence on concrete properties is considered as minor. Finally, the absorption and morphology of recycled aggregate depend on the granular fraction. Correlation between morphological and mechanical properties with water absorption have been demonstrated. After analysing these properties, correction were proposed on mechanical performance forecasting models. It was also shown that the use of fines in recycled aggregate concretes provides better mechanical properties. For such materials, keeping aggregates less than 63μm is advisable because it provides correct granular skeletton. In order to balance the loss of workability and mechanical strength observed with the use of recycled aggregates, studies were carried with several superplasticisers. Polycarboxylates were identified as appropriate superplasticisers. Interpretations facilitate understanding of concrete formulation and concrete equivalent mortar formulation made with recycled aggregates. Thus, the complexity of absorption and desorption kinectics lead to a discusion around effective water definition. The difference between the morphology of recycled aggregates and natural ones involved a correction of the granular skeletton; finally, their weakness during mechanical test modifies the granular skeletton and need to be taken into consideration.Finally, studies on environmental impacts of recycled aggregates concrete were done and compared with those of natural aggregates concrete. This study starts interesting perspectives

Le béton, largement utilisé dans la construction, est essentiel à la société moderne. Cependant, lorsque les bâtiments arrivent en fin de vie, la démolition devient inévitable, contribuant ainsi à l'accumulation annuelle des débris de béton. Cette situation pose un défi majeur en matière de gestion des déchets de construction. Face à cette réalité, le recyclage du béton émerge comme une nécessité. Cette approche permet non seulement de réduire la quantité de déchets envoyés en décharge, mais aussi de préserver les ressources naturelles, favorisant une construction plus durable. Cette thèse s'inscrit dans le cadre d'un projet de recherche centré sur le recyclage du béton dans une perspective d'économie circulaire. Elle propose une étude approfondie de la régénération des propriétés hydrauliques des matériaux cimentaires, avec pour objectif de comprendre les mécanismes impliqués à cette régénération. Cette analyse se déroule en trois étapes distinctes. Tout d'abord, nous avons examiné une phase pure de C3S, suivi par une phase intermédiaire utilisant du ciment Portland, pour finalement conclure avec une étude sur les bétons recyclés issus de retours et de déconstructions.Nous proposons un processus basé sur le traitement thermique des poudres issues du concassage des matériaux cimentaires, effectué à des températures basses allant de 400 °C à 800 °C. Des techniques de caractérisation comme l’ATG, l’IRTF, le RMN 29Si et la DRX avec la méthode Rietveld (TOPAS V6), ont été utilisées pour comprendre les mécanismes de régénération de l'hydraulicité.Les traitements thermiques appliqués aux différentes phases à partir de 600 °C ont révélé la formation de bélite. Plus précisément, le polymorphe β-C2S s'est formé dans le cas de la phase pure, tandis que les polymorphes α'-C2S et β-C2S se sont formés dans le cas de la pâte de ciment Portland. Les traitements thermiques appliqués sur les bétons de retour et de déconstruction ont révélé des mécanismes similaires, avec la formation de bélite observée à partir de 700 °C. Ces découvertes ont été confirmées par la diffraction des rayons X (DRX) et la spectroscopie RMN 29Si, cette dernière ayant également montré que les C-S-H sont complètement décomposés à cette température, conduisant à la formation de bélite.Les phases régénérées montrent une réactivité élevée, probablement en raison de la forte réactivité de la chaux produite pendant les traitements thermiques. Par conséquent, presque toute la bélite formée a été consommée après 28 jours d'hydratation. Les liants obtenus à des températures comprises entre 600 et 800 °C ont conduit à la reformation d'hydrates tels que les C-S-H, la Portlandite et l’Ettringite.Les mortiers fabriqués avec 100 % de liants issus des traitements thermiques appliqués aux pâtes de ciment ont dépassé 16 MPa en compression après 90 jours et peuvent atteindre plus de 30 MPa lorsqu’ils sont remplacés à 40 % par du CEM I, malgré leur forte demande en eau. En revanche, les mortiers composés de 100 % de liants issus de béton ne dépassent pas 4 MPa en compression après 90 jours, mais peuvent atteindre plus de 20 MPa en compression et 5 MPa en flexion lorsqu’ils sont remplacés à 40 % par du CEM I
Concrete, widely used in construction, is essential to modern society. However, as buildings reach the end of their life cycle, demolition becomes inevitable, contributing to the annual accumulation of concrete debris. This situation presents a major challenge in construction waste management. Faced with this reality, concrete recycling emerges as a necessity. This approach not only reduces the amount of waste sent to landfills but also preserves natural resources, promoting sustainable construction.This thesis is part of a research project focused on concrete recycling from a circular economy perspective. It offers an in-depth study of the regeneration of hydraulic properties of cementitious materials, aiming to understand the underlying mechanisms of this regeneration. This analysis is performed in three distinct stages. Initially, we examined a pure phase of C3S, followed by an intermediate phase using Portland cement, concluding with a study on recycled concretes from returns and demolitions.We propose a process based on the thermal treatment of powders derived from crushing cementitious materials, conducted at low temperatures ranging from 400°C to 800°C. To understand the mechanisms of hydraulicity regeneration, characterization techniques such as TGA, FTIR, 29Si-NMR, and XRD with the Rietveld method (TOPAS V6) were employed.Thermal treatments applied to various phases from 600°C revealed the formation of belite. Specifically, the β-C2S polymorph formed in the case of the pure phase, while the α'-C2S and β-C2S polymorphs formed in the case of Portland cement paste. Thermal treatments applied to returns and demolition concretes revealed similar mechanisms, with belite formation observed from 700°C onwards. These findings were confirmed by X-ray diffraction (XRD) and 29Si-NMR spectroscopy, the latter also showing complete decomposition of C-S-H at 600°C, leading to belite formation. The regenerated phases exhibit high reactivity, likely due to the strong reactivity of lime produced during thermal treatments. Consequently, almost all formed belite was consumed after 28 days of hydration. Binders obtained at temperatures between 600 and 800°C led to the reformation of hydrates such as C-S-H, Portlandite, and Ettringite.Mortars made with 100% binders from thermal treatments applied to cement pastes exceeded 16 MPa in compression after 90 days and could reach over 30 MPa when replaced by 40% CEM I, despite their high water demand. Conversely, mortars composed of 100% binders from concrete do not exceed 4 MPa in compression after 90 days but can reach over 20 MPa in compression and 5 MPa in flexion when replaced by 40% CEM I

In the process of crushing concrete waste, significant amounts of fine by-products, the so called fine recycled concrete aggregates (FRCA), are generated and excluded from potential use. Limited research has thoroughly investigated the performance of concrete mixes with FRCA, very likely due to the complexity in analysing non-negligible amounts of adhered residual cement paste (RCP). Although some studies have proposed promising sustainable mix-design procedures accounting for the different microstructure when using coarse recycled concrete aggregates (CRCA), no similar approach exists for FRCA concrete. In this work, two promising procedures for mix-designing eco-efficient concrete with 100% FRCA are proposed accounting for the presence of RCP to reduce cement content in new mixtures. First, built on top of the existing procedure for CRCA mix-design, modifications to the Equivalent Volume (EV) method were introduced toconsider full replacement of fine natural sand by FRCA. Second, based on the concept of continuous Particle Packing Models (PPM), an optimized procedure was proposed to allow maximum packing density of FRCA mix linked to a given level of measured RCP content. Results verified the feasibility of producing eco-efficient concrete mixes with 100% FRCA, emphasizing the PPM mixes to report superior rheological and mechanical performance along with suitable durability-related properties. Yet, results also indicated the influence of simple or multistage crushed FRCA on the overall performance of mixes.

The use of recycled aggregate in the production of self-compactig concrete (SCC) is relatively recent. Few studies have been developed, but, there are numerous advantages in its application. The recycled lightweight self-compacting concrete (RLSCC) offers several advantages of SCC, due to the self-compacting properties, it absorbs construction residues, in the use as recycled aggregates, and the lightness due to the smaller specific mass of the recycled aggregates, it promotes the reduction of the loads due to the own weight . However, studies carried out in concrete with recycled aggregates (RA) have shown to be very complex due to the characteristics of these aggregates, such as: high porosity, high water absorption, irregular shape, rough surface, etc. These characteristics tend to lead to mixtures with less workable and lower mechanical strength. In this way, the study had as objective to obtaining the RLSCC, separate the process in two steps: aggregates and mortar. Where, the characterization of the RA is the way to understand its characteristics and the limitations that it will impose in the mixture of concrete. The study of mortars, to verify a composition with the best parameters of fluidity and rheological, since the difficulty faced by researchers in obtaining workable mixtures. Thus, it was verified that the standardized characterization methodologies, for natural aggregates, face some difficulties in their application in recycled aggregates, rendering them inefficient. The characteristics of the recycled aggregate could be attenuated with a composition study, reaching very workable mortars, with low yield stress and moderate viscosity. The SCC was obtained through a study of maximum content of recycled coarse aggregate, through concrete tests. The obtained concrete presented compression strength of 30 MPa and apparent specific mass of 2000 kg/m³, classifying it as concrete of structural application and light.
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A utilização de agregado reciclado na produção de concreto autoadensável (CAA) é relativamente recente. Poucos estudos têm sido desenvolvidos, mas, observam-se inúmeras vantagens em sua aplicação. O concreto autoadensável leve reciclado (CAALR) oferece diversas vantagens do CAA, devido às propriedades de autoadensabilidade, absorve resíduos de construções, na utilização como agregados reciclados, e a leveza devido a menor massa específica dos agregados reciclados, promove a redução das cargas devido ao peso próprio. No entanto, estudos realizados em concreto com agregados reciclados (AGR), têm se mostrado muito complexos devido às características destes agregados, como: elevada porosidade, alto teor de absorção de água, forma irregular, superfície rugosa, etc. Características estas que tendem a conduzir a misturas pouco trabalháveis e de resistência mecânica inferior. Desta forma, o estudo teve como objetivo a obtenção CAALR, separando o processo em duas etapas: agregados e argamassa. Onde, a caracterização do AGR é o meio para o entendimento de suas características e das limitações que ele irá impor na mistura de concreto. Já o estudo de argamassa, o objetivo foi verificar uma composição com os melhores parâmetros de fluidez e reológicos, visto as dificuldades enfrentadas por pesquisadores em obter-se misturas trabalháveis. Assim, verificou-se que as metodologias de caracterização normatizadas, para agregados naturais, enfrentam algumas dificuldades na sua aplicação em agregados reciclados, tornando-as pouco eficientes. As características do agregado reciclado miúdo puderam ser atenuadas com um estudo de composição, chegando a argamassas muito trabalháveis, com baixa tensão de escoamento e viscosidade moderada. A obtenção do CAA foi possível, através de um estudo de teor máximo de agregado reciclado graúdo, através de ensaios em concreto. O concreto obtido apresentou resistência de 30 MPa e massa específica aparente de 2000 kg/m³, classificando-o como concreto de aplicação estrutural e leve.

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SINDUSCON-NH - Sindicato das Indústrias da Construção Civil Novo Hamburgo
A construção civil atualmente é a indústria com maior crescimento no Brasil, fomentada por financiamentos e programas do governo federal. É também uma das indústrias que mais consome recursos naturais e energia, além de ser a principal geradora de resíduos sólidos urbanos. Grande parcela destes recursos naturais consumidos pela construção é formada pelos agregados. Uma alternativa econômica e ambientalmente correta, para diminuir a extração deste material, é a sua substituição por algum outro material, se possível por um resíduo, como apontam várias pesquisas. A busca por materiais e produtos ecologicamente corretos está em uma crescente, assim como os estudos para a reciclagem de diversos resíduos. A união entre produtos que consomem um volume menor de matéria-prima com o emprego de resíduos na sua produção parece uma saída viável para um desenvolvimento mais sustentável. Artefatos para a construção civil produzidos com concreto celular autoclavado (CCA) utilizam até quatro vezes menos materiais quando comparados a produtos com características semelhantes, produzidos com concreto convencional, cerâmico, entre outros. Além do menor consumo dos materiais constituintes, o concreto celular possui outras propriedades interessantes, como: suficiente resistência à compressão; isolamento térmico e acústico; baixa densidade; resistência ao fogo. Esta pesquisa teve como objetivo principal avaliar a influência da substituição parcial do agregado natural por agregado reciclado de concreto (ARC) na produção de concreto celular autoclavado. Após realização de estudos-piloto, optou-se pelo emprego da proporção de Cimento e Agregado Natural (AN) de 67% e 33% e sobre estes 0,45% de Cal e 0,3% de Alumínio com relação água/sólidos igual a 0,32. Foram empregados Cimento Portland CP-V ARI, Cal calcítica, areia natural e agregado fino reciclado de concreto, em teores de 0%, 25% e 50%. A dimensão máxima do agregado empregado na produção de CCA é de 150 µm. A cura foi realizada em autoclave após um tempo de espera de 24 horas a partir do início da mistura, por um período de 6 horas. Foram avaliadas a resistência à compressão, a absorção de água capilar, a massa específica e a porosidade. Os ensaios de resistência à compressão foram realizados em 48 e 72 horas, e a absorção de água, em corpos de prova preparados e acompanhados pelo período de 96 horas. A microestrutura dos CCA produzidos foi caracterizada por microscopia eletrônica de varredura (MEV). Verificou-se que existem expressivas alterações nas propriedades do CCA produzidos com ARC em substituição do AN, com a tendência de aumentar a densidade de massa aparente, bem com a resistência à compressão, a medida que aumenta-se o teor de ARC. Na análise dos resultados, percebeu-se que o uso de ARC alterou as propriedades dos concretos produzidos neste estudo exploratório, sem, entretanto, inviabilizar o seu emprego. Com um ajuste da dosagem, pode ser obtido um CCA produzido com ARC, cujo comportamento seja compatível com o comportamento de CCA produzido somente com o AN.
In the last years, the Brazilian construction industry is among those of national production sectors that have been having a great growing, mostly due to the incentive from the government and due to financed resources by private and public agents. This industry is also one of the major consumers of natural resources and energy, besides being the main generator of solid waste. One of these natural resources used in the constructions is sand. An environmentally friendly and economical alternative to reduce the extraction of natural resources is the use of recycled waste. The associated use of low volume of raw materials with alternative materials, like waste, is one of the ways to get more sustainability in the construction sector. Construction and building components made with autoclaved cellular concrete (ACC) employ four times less material than others with the same function. Other advantage of ACC is the performance of its properties like compressive strength, thermal and acoustic behavior, lower density, fire resistance. The aim of this research was to investigate the use of fine grains from recycled concrete aggregate (ARC) as partial sand replacement in the production of autoclaved aerated concrete. With the goal to find the mix proportion some pilot studies were made. After this, it was chosen a relation of 67% of cement and 33% of natural fine aggregate (sand). The lime was used in the amount of 0.45% of total cement and sand, and 0.3% of aluminium. The water to total solids ratio was 0.32. It was employed Portland cement type V according to Brazilian standards, calcitic lime, natural sand and ARC passing in sieve with 150 micron opening. The replacement rate of sand by ARC was 0%, 25% and 50%. From 24 hours after the mixing of materials, the samples were submitted to steam curing in an autoclave chamber for 6 hours. It was evaluated the compressive strength, the density, the capillary water absorption and porosity. The compression strength tests were performed at 48 and 72 hours. Water absorption tests were conducted for 96 hours after samples preparing. The capillary porosity was calculated with the capillary water absorption data. ACC's microstructure analysis was done by scanning electron microscopy (SEM). The results showed in general that the behavior of ACC produced with ARC differs significantly from the ACC produced with natural aggregate. When the ARC rate increases the apparent specific gravity also increases as well as the compressive strength. The observed increase in the apparent specific gravity is not desired. However this behavior of ACC done with RCA does not prevent the use of this recycled aggregate. An optimized study of pre-wetting of RCA could improve its performance as aggregate for use in ACC, once its grain size showed to be appropriated for this kind of use.

Ce travail de thèse combine des approches expérimentales et théoriques visant à caractériser les propriétés mécaniques et de durabilité des bétons à base de granulats recyclés. La première partie est consacrée à la quantification de l'effet des granulats recyclés sur les propriétés mécaniques et de durabilité de ces bétons. Les résultats montrent que les propriétés mécaniques et de durabilité des bétons à base de granulats recyclés sont sensibles non seulement aux propriétés physiques des granulats recyclés mais aussi à leur quantité au sein de la microstructure. Par ailleurs, une caractérisation des propriétés mécaniques locales grâce aux essais de nano indentation et micro indentation a aussi été entreprise; ce qui a permis d'avoir accès aux propriétés mécaniques des phases telles que les zones d'interface ou encore l'ancien mortier. La deuxième partie est une approche consacrée à l'établissement des modèles multi-échelles en mesure de rendre compte des propriétés macroscopiques (mécanique et de diffusion) des bétons à base de granulats de démolition en tirant profit des informations recueillies sur la microstructure (observation au microscope, nano et micro indentation,...). Une prise en compte du caractère complexe des granulats recyclés a aussi été abordée dans ce développement théorique. Enfin, une comparaison des résultats des modèles avec ceux expérimentaux est présentée puis discutée dans ce travail
This thesis combines experimental and theoretical approaches to characterize the mechanical and durability properties of recycled aggregate concretes (RAC). The first part of the work is devoted to the quantification of the impact of recycled concrete aggregates on the mechanical and durability properties of RAC. The results show that mechanical and durability properties of recycled aggregate concretes depend not only on the physical properties of recycled concrete aggregates but also on their quantity in the microstructure. Furthermore, statistical indentation technique is used to capture the local mechanical properties of phases in the microstructure of RAC such as the interfacial transition zones and the attached mortar. The second part of this study deals with the multi-scale modeling of the mechanical and the durability properties of RAC. The main purpose of this theoretical work is to establish models capable to predict the macroscopic behaviour based on the available information on the microstructure (obtained by optical microscopy or through indentation technique). The established models take into account the complex structure of the recycled concrete aggregates. Finally, the results of the models are compared with experimental data for discussion

The use of recycled concrete aggregates (RCA) has gained increased attention in the past few decades as an alternative to decrease the carbon footprint of concrete construction. Yet, most of the research performed so far demonstrates that RCA concrete displays inferior performance in the fresh and hardened states when compared to conventional concrete (CC). The latter is believed due to the fact that very often the different microstructure of RCA is not accounted for while the mix-proportioning of RCA concrete. Recently, a number of mix-design procedures accounting for RCA microstructure have been proposed. Amongst them, the Equivalent Volume (EV) method seems to be quite promising. The EV method may proportion RCA concrete made of coarse (CRCA) or fine (FRCA) RCA and is based on a companion CC. Previous research has demonstrated that the fresh and hardened properties of EV mix-designed CRCA are suitable for structural applications. Yet, very few research, analysis and quantification have been conducted on the fresh behaviour of EV mix- proportioned FRCA concrete. This work presents a comprehensive study on the rheological behaviour of EV mix-designed CRCA and FRCA concrete presenting distinct features (i.e. inner qualities, mineralogy, fabrication process, etc.) through the use of a planetary rheometer (IBB). Results show that the EV is capable of proportioning low embodied energy CRCA and FRCA concrete with shear thinning profiles. The latter suggests that these mixtures are suitable for applications under high torque regimes such as vibrated or pumped concrete.

With more than three tons per head, per year, concrete is the most important and widespread material used in construction worldwide. The Italian code allows the use of waste produced by construction and demolition (C&D) operations to produce recycled aggregates. The great interest, both technical-economic and environmental aroused by this subject has in recent years and all over the world led to a noteworthy increase in experimental and theoretical studies on recycled materials resulting from the construction sector and, in particular, on recycled aggregates. The possibility of utilizing recycled aggregate is a very good solution to the problem of C&D waste and at the same time it reduces quarrying operations and limits the use of natural aggregates. The Italian ministerial decree of 14 January 2008 containing technical regulations for construction works, together with UNI EN 12620 and UNI 8520-2 standards concerning structural materials now allows a limited replacement percentage of only coarse recycled aggregates (sizes above 4 mm), to produce structural recycled concrete. In this scenario, the research activities described herein were developed with the final purposes of: Characterizing “real” coarse and fine recycled aggregates derived from construction and demolition waste by only concrete, randomly taken from an authorised class A storage site. This characterization was performed to determine their performance, compliance with the Italian code and the best experimental practice for the production and use in structural concrete. Furthermore the characterization of recycled aggregates by means of their shape, sizes, density, structure, strength, permeability and resistance to freezing and thawing cycles, directly leads to CE+2 certification, which is not present in Sardinia at the moment. Analysing different concrete mixtures made with different replacement percentages of fine and coarse and only coarse recycled aggregates in place of the natural ones to create a product having good properties during production, transport and implementation, with good compatibility with all devices and machines employed in concrete plants. The intention is to use recycled aggregates produced exclusively by concrete, coming from authorized class A storage sites, immediately after their release from the crusher and to optimize the mix design of the recycled concrete and the relative packaging procedure. Determining the mechanical properties of recycled concrete made with different replacement percentages of coarse and fine and only coarse recycled aggregates and comparing them with ordinary concrete to measure the gap in performance and evaluating their use in structural concrete. Reviewing and examining the scientific scenario in the determination of mechanical properties of the transition zone (ITZ). The results obtained from characterization of fine and coarse recycled aggregates, show a variability in line with what usually occurs in the characterization of natural aggregates, especially for coarse aggregates. The CE marking of recycled aggregates from concrete only, now completely absent in Sardinia, appears to be a feasible goal. However, a complete reorganization of demolition companies with selective demolition and separation of C&D waste is essential, together with a reorganization of authorized storage sites. Experimental results show a generally good behaviour of fresh and hardened recycled concrete. In concrete made with only coarse recycled aggregates, for very high replacement percentages of 50% and 80%, the differences with the strength properties of ordinary concrete are minimal, and sometimes irrelevant. In concrete made with fine and coarse recycled aggregates a reduction in strength was found, but was contained for replacement percentages up to 50%. Fine recycled aggregates present more problems compared to coarse recycled aggregates, especially as regards water absorption and particle size distribution. Their use in practice is possible if the dosage of water, cement and additives to be included in the mix is studied in advance. The study of the mix in producing concrete, and in particular for recycled concretes, plays a role of fundamental importance. The excellent results obtained in this experimental work, in terms of workability and strength are probably for the most part to be attributed to the choices made in this stage, mostly as concerns the choice of the additive and the amount of compensating water added to the mixtures. An important result of the experiments performed concerns the possibility of producing structural concrete using real coarse and fine recycled aggregates coming exclusively from the waste crushed concrete, immediately as it comes out of the crusher, without the need to optimise the grain size curve. However, an optimal mix design must be arrived at, especially as concerns the W/C ratio and the quality and quantity of additive used.

This research demonstrates that rubber particle size affects concrete workability and water permeability to a greater extent than fresh density and strength. Concrete with rubber particles of larger size tends to have a higher workability and fresh density than that with smaller particle sizes. However, rubber aggregates with smaller or continuously graded particle sizes are shown to have higher strengths and water permeability resistance. Influence of recycled aggregate and rubber aggregate as part substitutions for natural aggregates on concrete compressive strength was investigated and four equations were proposed to predict compressive strength of the designed concrete. Besides, it is experimentally shown that silane coupling agent (SCA) has a positive effect on reducing the loss of strength of rubber concrete, especially when concrete is weak. This effect becomes more significant with the increase of mass fraction of SCA solution. Experiment results also show a better performance of concrete with SCA-treated rubber than with as-received or sodium hydroxide solution (NaOH)-treated rubber. A brief cost analysis suggests that this approach of surface modification is economically viable. Referring to a provided fatigue load spectrum and fatigue failure mechanism, this method is potentially to be used for rubber concrete in high-cycle fatigue condition.

In order to reduce the use of landfilling within waste management great emphasis is being placed on waste reduction and recycling. Each year in the UK approximately 2.5 Mt of waste glass is produced and approximately half of this waste is not recyclable. Therefore alternative ways need to be found for using waste glass and one possibility is to use it within concrete as a replacement for cement and/ or aggregate. In the research programme concrete mixes were tested which had 0%, 25%, 50% and 100% of the fine aggregate replaced by crushed waste glass. All glass was originally in bottle form and was crushed to produce ‘sand’ which had a grading curve more-orless identical to fine aggregate obtained from a commercial supplier. Three colours of glass were studied, i.e. flint (clear), amber and green. Concretes were also made which contained a mixture of colours (in proportion according to the weight of each type of waste glass produced annually within the UK) and also a mixture of unwashed waste glasses. The overall concrete mix adopted for investigation, i.e. 1:2:4, was selected because of its wide use within industry, and all concrete was made with a water:cement content of 0.6 without the addition of plasticiser or ASR-retarding agents. The suite of laboratory tests included; slump, flow, initial and final setting time, ultrasonic pulse velocity, water absorption by immersion and capillarity rise, ASR measurement (volumetric and linear), compression strength at ages from 7 days to 365 days. Techniques of developed digital imaging and processing have been applied to the glass aggregate to quantify various particle shape factors, i.e. aspect ratio, percentage concavity, Riley inscribed sphericity and surface texture index. Statistical analysis has been used to compare the distribution of particle forms present within the fine aggregate materials used in the experimental work. Dimensional changes (in three orthogonal directions) were measured as concrete cubes hardened over a period up to 365 days. The length changes of concrete prisms were also measured over the same period of time. The resultant data indicated that a fine aggregate which comprised 25% glass and 75% sand would be categorised as “non-expansive”, i.e. the same as the sand on its own. As the proportion of glass in the fine aggregate became greater than the aggregate became more expansive but it did not exceed recommended limits.

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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
CNPQ – Conselho Nacional de Desenvolvimento Científico e Tecnológico
FINEP - Financiadora de Estudos e Projetos
A construção civil é um dos setores que mais consome recursos naturais não renováveis, além de ser um dos principais geradores de resíduos sólidos urbanos (RSU). Dentre os diversos recursos naturais extraídos da natureza, os agregados utilizados na construção civil são os insumos minerais mais consumidos no mundo. Com a crescente restrição da extração de areias dos rios e a escassez de areias naturais é essencial que o setor da construção venha a adotar uma postura ambiental e sustentável, através de desenvolvimentos tecnológicos de processos de reciclagem de resíduos. Uma das alternativas para a construção civil, tanto do ponto de vista econômico quanto ambiental, no abastecimento de areia para a construção é a substituição das areias extraídas dos rios (areia natural) por resíduos de concreto, para a produção de argamassas. Este estudo tem como objetivo principal avaliar o comportamento de argamassas de revestimento com incorporação de agregado miúdo reciclado de concreto (AMRC), em substituição à areia natural extraída de rio (AN). Os AMRC foram obtidos a partir de resíduos de dois tipos de concreto empregados na pré-fabricação: de concreto submetido à cura térmica à vapor (ARCT) e outro de concreto submetido à cura convencional (ARCC). As argamassas foram confeccionadas com cimento CP II Z– 32 e cal CH-I, empregando-se traço em volume 1:1:6 com índice de consistência fixado em 260 ± 5 mm, para as três misturas de argamassas. O estudo foi desenvolvido em duas etapas. Na primeira etapa foram analisadas a caracterização morfológica e a distribuição granulométrica das areias. Na etapa seguinte analisou-se o comportamento e características das argamassas no estado fresco e no estado endurecido. A análise das argamassas no estado fresco contemplou dados de índice de consistência, penetração de cone, squeeze flow, retenção de água, densidade de massa e teor de ar incorporado. No estado endurecido as propriedades estudadas foram densidade de massa, resistência à compressão, resistência à tração na flexão, absorção de água por capilaridade e coeficiente de capilaridade, absorção de água, índices de vazios, massa específica, módulo de elasticidade dinâmico e porosidade por intrusão de mercúrio. Verificaram-se diferenças significativas no comportamento das argamassas confeccionadas com os dois agregados reciclados. No estado fresco foi observado perda de trabalhabilidade; perda de densidade de massa; aumento de ar incorporado, com perdas mais expressivas para a mistura com ARCC. No estado endurecido observou-se redução da resistência à compressão e da resistência à tração na flexão para as argamassas com ARCC. Os dados apontaram ainda diminuição de absorção de água por capilaridade; aumento da absorção de água por imersão; aumento do índice de vazios; aumento da massa específica e redução do módulo de elasticidade dinâmico para ambas as argamassas com agregados reciclados.
The construction industry is one of the sectors that consume non-renewable natural resources, besides being one of the main generators of municipal solid waste. Among the various natural resources extracted from nature, the aggregates used in construction are the most consumed mineral inputs in the world. With the increasing restriction of sand extraction from rivers and the scarcity of natural sands it is essential that the construction industry adopt an environmental and sustainable development, through technological processes to recycle waste. One of the alternatives to the construction industry, from an economical and environmental point of view, the supply of sand for construction is the replacement of sand extracted from rivers (natural sand) for concrete waste, for the production of mortars. This study aims at evaluate the behavior of rendering mortar with incorporation of recycled aggregate concrete, replacing the natural sand. The morphological characteristics and composition of two aggregates made from concrete were analysed: one from concrete subjected to thermal curing and other to conventional curing, compared with a river sand. Characterization tests were performed on fresh mortar (consistency index, cone penetration, squeeze flow, water retention, density and air content) and hardened mortar (density, compressive strength, flexural strength, capillarity water absorption and capillarity coefficient, water absorption, density, dynamic modulus of elasticity and mercury intrusion porosimetry). For this experiment were followed the requirements of NBR 13281 (ABNT, 2005) and used Brazilian CP II Z-32 cement and CH-I lime. A proportion of 1:1:6 (cement, lime and sand) by volume, with index consistency set at (260 ± 5) mm was adopted for the three mixtures of mortars. There were significant differences in the behavior of the two mortars made with recycled aggregates, such as: loss of workability; loss of density; increased air content (especially mixing with ARCC), in fresh stage. Reduction of compressive strength and reduced flexural strength (except in the mixture with ARCT), reduction of water absorption by capillarity, increased water absorption by immersion, an increase in the index of emptiness, increased density and reduced dynamic modulus of elasticity, in the hardened mortar.

碩士
國立臺灣海洋大學
材料工程研究所
102
This study was focused on the mechanical and physical properties and durability in the modified mortar which the fine aggregates were partially replaced by recycled fine aggregates. Proper replacement of fine aggregates by recycled fine aggregates would reduce use of natural resources. This study mainly used various durability test to investigate in specimens with various water/cement ratio, various recycled fine aggregates content. Properties such as compressive strength, abrasion resistance, ultrasonic pulse velocity, water absorption, initial surface absorption, electrical resistivity, resistance to sulfate attack were also examined. Test results indicate that different water-cement ratio, two kinds of recycled fine aggregates, replacement of 25%, similar to the compressive strength and the control group. When the amount exceeds 50% replacement, Properties of the cementitious material will decrease as the water-cement ratio,and the amount of recycled fine aggregates replaced by a increase. The greater the amount replaced in the higher the surface water absorption, the lower the compressive strength and durability. The replacement percentage is the controlled surface water absorption and compressive strength, durability. The replacement percentage from low value to high value are ranked as control group, R1A group, R2A group, R1B group, R2B group, R1C group, R2C group.

碩士
中原大學
土木工程研究所
96
Abstract The government suspended the exploiting of sand and gravel in Taiwan's main streams. The difficulty of obtaining a stable supply of aggregates causes their prices to go up dramatically. On the other hand, huge amount of construction discards are produced every year, causing pollutions and destructions to the environment. Secondly, dumping grounds for construction discards are difficult to find. As environmental consciousness of people rises, every country begins to pay more and more attention to sustainable usage of materials. Due to the factors stated above, transferring construction wastes into reusable materials is a definite act. This research is to study the effect of using construction brick-sand to replace fine aggregates in recycled concrete. Test results showed that using construction bricks as fine aggregates would enhance Pozzolan reaction, owing to the large proportion of SiO2 and Al2O3 contained in bricks. The Pozzolan effects were very obvious for concretes with water to cement ratio of 0.4: the compressive strength of recycled concrete with construction bricks as FA were closed to those with natural aggregates. For water ratio of 0.6, the reduction range is not very large, ranging from 0.7% to 20%. The crushed construction bricks had a very high percentage of dust (about 12%). The effect of brick dust on strength of concrete is studied by two groups of specimens: one with the 12% dust included and one with the dust washed away. For recycled concrete with water ratio of 0.4 and 100% replacement of brick sands, strength of specimen with dust is 1.2% higher than those without dust. However, for higher water cement ratio of 0.6, the strength is 10% higher.

碩士
中原大學
土木工程研究所
98
The objectives of this study are to find the compressive strength and ultrasonic pulse velocity (UPV) of recycled concrete with various percentages of natural fine aggregate replaced by recycled discarded tile as well as the residual strength and residual UPV of recycled concrete subjected to elevated temperatures. The effect of various fine recycled aggregate on concrete is investigated by lost of ignition (LOI). The testing results exhibit that the earlier-age compressive strength of recycled concrete will decrease depending on the increase of discarded tiles. The experimental results reveals that recycled concrete had better long-term performance. The recycled concrete replaced with 25% discarded tile is superior than control specimen on compressive strength at all curing ages, either the cement to water ratio is 0.4 or 0.6. However, the remaining substitute amount is superior than the opposing one at the medium/late stages in terms of compressive strength, it shows that the higher ratios of substitute represent the more apparent effects at the medium/late stages of pozzolanic reaction. The result of UPV test could evaluate the density of cement paste of concrete, the longer ages it is, the faster wave speed it imposes, representing that the relative compressive strength of inner density has been increased consequently. LOI is a method to measure the amount of hydration products; bigger amount means great creation of such element, it relative compressive strength becomes incremental trend, this condition is apparent at the medium/late stages. In the high temperature test, when heating to 300℃ under 28 days age, the incremental ratio of compressive strength is that of 25℃ by 4%~16%, whereas it is by 0.8%~6% under 300℃, 91 days age. In other words, the high temperature and immature response may accelerate the hydration, at the late stage; the mature response may decelerate the promotion ratio of compressive strength. As under 440℃、580℃、800℃, the compressive strength will decrease depending on the incremental ratio of heat due to the decomposition of inner hydration products. With respect to high temperature ultrasonic, due to the decomposition of water and its hydration products, hence,the wave speed would decreases while the temperature increase. Besides, it is found that the compressive strength are close between conditions of conditions of 300℃ in the age of 28 days and 300℃ in the age of 91 days. There are seven master dissertations of Chung Yuan University to verify this outcome, and the discovery is that: in case of coarse aggregate, the difference ratio of compressive strength between the two will be within 10%; in the case of fine aggregate substitute, the ratio is within 20%. There are three relatively obvious conditions in the study, 1. The greater substitute amount of find structure it uses, the more slump it will have; 2. The compressive strength of 25% is superior than the opposing one, either ratio 0.4 or ratio 0.6; 3. At the age of 180 day, the greater substitute ratio of fine structure it has, the more compressive strength it will perform.

碩士
國立宜蘭大學
土木工程學系碩士班
103
This study investigated the mechanical properties and durability of concrete produced using recycled fine aggregate (RFA) pre-coated with fly ash, slag, and a polymer solution (PVA). We investigated the physical and microscopic properties of fresh concrete, while adjusting several of the fabrication parameters, such as the constituent make up and thickness of RFA pre-coatings. The study is divided into two parts. The first part involves mortar testing in which the RFA used for coating had a water/cement ratio of 0.5 and fly ash, slag, and PVA viscosity of 5~6cps, 21~26cps, 25~30cps, or 44~50cps. In these tests, 100% of the natural fine aggregate was replaced by RCA. The second part of the study involved the mixing of concrete with 25% FRA, which was respectively coated with fly ash, slag, or PVA at a viscosity of 44~50cps. In these tests, the water/cement ratio was either 0.4 or 0.6. The major findings in this study are summarized as follows：Coating RFA coated with fly ash and PVA was shown to increase flow in the fresh concrete; however, the coating of RFA with slag resulted in a slight decrease in flow. Coating RFA with slag was shown to improve the compressive and splitting strength to a greater degree than that achieved by coating RFA with fly ash and PVA. The mechanical properties of concrete mixed with slag were shown to increase with the thickness of the coating. Coating RFA with slag was also shown to enhance the durability of the concrete, regardless of the water/cement ratio.

碩士
朝陽科技大學
營建工程系碩士班
99
Abstract The research was conducted to study the mechanical property of concrete using fine aggregate substituted with the sedimentary soils retrieved from Wu-Shey reservoir in Ren-Ai, Nantou County, Taiwan. Laboratory tests in the study include fundamental physical property, compression strength, ductility and abrasion resistance characteristics at curing time of 7 and 28 days with water/cement ratio of 0.5, 1.0 and 1.5. The main purpose of the research was to study the feasibility of using the reservoir sedimentary soils as fine aggregate for concrete mix to reduce the cost of removing the sedimentary soils and maintain the storage capacity of the reservoir. The results of the tests revealed that the compression strength of the concrete mixed with the reservoir sedimentary soil at 28 day ranges from 49 kg/cm2 – 248 kg/cm2 at the selected water/cement ratios, which are about 54%-64% of the regular concrete mixed with standard natural aggregate commonly used in practice. Based on the results of the study, the research preliminarily suggests that the sedimentary soils can be used in non-standard concrete for some construction projects such as gravity-type retaining wall, and flood control and stream regulation facilities for rivers in the reservoir area. In addition, the mechanical properties of the concrete using the sedimentary soils also meet the criteria for application in controlled low strength material (CLSM), farmland pedestrian passage with width less than 4 meter, and rigid pavement for light traffic in rural areas. The results of the study provide useful information for better understanding of mechanical property and value of the sedimentary soils as to more effectively manage the reservoir storage capacity.

碩士
中原大學
土木工程研究所
99
In this research, recycled concretes are made according to field mix design used in ready-mixed concrete plant with discarded concrete blocks (as coarse aggregates) and discarded tiles (as fine aggregates). Moreover, the ratio of cement and pozzolanic admixture (fly ashes and stove stones) within recycled aggregates specimens are adjusted as well. Meanwhile, the water to binder ratio of pozzolanic admixture does not increased for more than 25%. Slump test according to ASTM C143, chloride experiment, compressive strength test, supersonic wave experiment, and high temperature test are carried out in the same environment and allocated percentages, and the differences between recycled concretes and natural fine aggregate concretes are studied. Results of the tests show that the early reaction of recycled fine aggregate concrete is faster than nature fine aggregate concrete. No matter what percentage of water to binder ratio, the strength of recycled fine aggregate concrete is higher than natural fine aggregate concrete. While talking about the strength, there is not much difference in the age of 7-days recycled fine aggregate concretes with different percentage of water to binder ratios; however, there are significant differences in the later period. In the early age, the differences between the strength of recycled fine aggregate concrete added with pozzolanic admixture materials and the strength of concrete which made by recycled pure fine aggregate cement is within 10%. Besides, recycled concretes which made by certain percentage of stove stones and fly ashes is higher than recycled concretes made by pure cements for about 6%. The development of 28-days recycled concretes is gradually slow; but the development of recycled fine aggregate concretes with no pozzolanic admixture is more slower. Nevertheless, the strength of nature fine aggregate concretes increased with certain percentage after 14 days of age. In the later stage for about 91 days, the rest of the recycled concretes reach 90% strength of nature concretes, excluding the recycled concretes made by stove stones and ashes. It is known that the pozzolanic admixture materials not only has significant influence upon the strength of nature fine aggregate concretes, but also do help the specimens made by recycled tiles.