This paper presents results on experimental research for concrete produced using recycled coarse aggregates (RCA). Five types of coarse aggregates were used in this study, four of which were RCA. The main purpose of this research was to examine how different types and properties of coarse aggregate affected compressive strength, modulus of elasticity, and shrinkage in concrete when natural coarse aggregates were replaced with RCA. Concrete batches were made with water-cement (w/c) ratios of 0.30, 0.45, and 0.60, and substitution percentages ranged from 0% to 100% of natural aggregate with RCA. Test results clearly show that compressive strength, modulus of elasticity, and shrinkage greatly depend on the quality and type of coarse aggregate used. In addition to testing of hardened concrete, predictive models for elasticity and ultimate shrinkage were developed to formulate and reinforce proposed conclusions about the properties and performance for the different RCA.

Yes / Demolition and reconstruction of degrading structures alongside with the repetitive repair, maintenance, and renovation applications create significant amounts of construction and demolition waste (CDW), which needs proper tackling. The main emphasis of this study has therefore been placed on the development of concrete mixtures with components (i.e., aggregates and binder) coming entirely from CDW. As the binding phase, powdered CDW-based masonry units, concrete and glass were used collectively as precursors to obtain geopolymer binders, which were then incorporated with CDW-based fine and coarse concrete aggregates. Together with the entirely CDW-based concretes, designs were also proposed for companion mixtures with mainstream precursors (e.g., fly ash and slag) occupying some part of the CDW-based precursor combination. Sodium hydroxide (NaOH), sodium silicate (Na2SiO3) and calcium hydroxide (Ca[OH]2) were used at various concentrations and combinations as the alkaline activators. Several factors that have impact on the compressive strength results of concrete mixtures, such as mainstream precursor replacement rate, al-kaline molar concentrations, aggregate-to-binder ratios and curing conditions, were considered and these were also backed by the micro-structural analyses. Our results showed that through proper optimiza-tion of the design factors, it is possible to manufacture concrete mix-tures entirely out of CDW with compressive strength results able to reach up to 40 MPa under ambient curing. Current research is believed to be very likely to promote more innovative and up-to-date techniques to upcycle CDW, which are mostly downcycled through basic practices of road base/sub-base filling, encouraging further research and increas-ing the awareness in CDW issue. / The full-text of this paper will be released for public view at the end of the publisher embargo on 1 Jul 2024.

The U.S. military must have the ability to rapidly deploy troops and equipment anywhere in the world as part of a contingency operation. Recent military operations have highlighted the critical need for rapid repair procedures and materials for military use on sub-standard, in-theater airfields. The U.S. Army Corps of Engineers, Engineer Research and Development Center is currently addressing these problems through a program titled ?Joint Rapid Airfield Construction?. This study involves the development of a method using rapid setting grouts and recycled concrete pavement (RCP) to repair portland cement concrete (PCC) pavements. A laboratory study was conducted to evaluate material properties in order to gain an understanding of expected field performance. Eight full scale repairs were constructed using two rapid setting grouts, two types of equipment, and two concrete slabs. The repairs were successfully trafficked with simulated C-17 aircraft wheel loads to verify the structural capacity, and ultimately the procedures.

A pesquisa teve como objetivo principal avaliar a incorporação de agregados reciclados de concreto em blocos estruturais de concreto para três classes de resistência (4,5 MPa, 8,0 MPa e 12,0 MPa). O estudo foi desenvolvido basicamente em quatro etapas. A primeira etapa consistiu na análise das propriedades físicas de agregados miúdos e graúdos reciclados de concreto originários de uma fábrica de pré-moldados. Na segunda etapa, foram analisadas as propriedades físicas e mecânicas de corpos-de-prova cilíndricos produzidos com concreto de consistência seca utilizando-se dois tipos de agregados reciclados previamente avaliados. O objetivo foi definir um intervalo de correlação entre a resistência à compressão de corpos-de-prova e blocos, verificar preliminarmente a influência dos agregados reciclados sobre as propriedades físicas e mecânicas e determinar os traços para a próxima etapa. Para a terceira etapa, foi avaliada a viabilidade técnica da produção de blocos com agregados reciclados através da análise de propriedades físicas e mecânicas, sendo também avaliada a viabilidade econômica pela proposição de algumas alternativas para reciclagem. De maneira geral, independentemente do grupo de resistência avaliado, todas as unidades com agregados graúdos reciclados cumpriram os requisitos estabelecidos; já para o estudo econômico, todas as hipóteses atestaram a viabilidade da produção de unidades com agregados reciclados com custos de produção e comercialização inferiores aos das unidades comumente produzidas. Finalmente, a quarta etapa, consistiu na avaliação da retração por secagem em miniparedes, resistência à compressão e módulo de deformação de elementos (prismas e miniparedes) produzidos com as unidades da etapa anterior. Em função dos resultados obtidos, pode-se afirmar que apenas a propriedade de retração por secagem foi afetada pelas unidades com agregados reciclados; nesse caso, a redução da distância entre juntas de controle foi considerada uma medida suficiente para minimizar os efeitos da retração por secagem. / The main goal of the present research project was the evaluation of recycled concrete aggregates incorporation in structural concrete blocks of three different levels of compressive strength (4,5 MPa, 8,0 MPa and 12,0 MPa). The study was developed in four stages. The first stage analyzed the physical properties of fine and coarse concrete aggregates derived from a precast concrete plant. In the second stage, physical and mechanical properties of dry consistency concrete cylindrical specimens were analyzed using two types of recycled aggregates. The aim was to define a correlation interval between the compressive strength of cylindrical specimens and concrete blocks, verify the influence of recycled aggregates on the physical and mechanical properties, and determine the better compositions to be used in the next stage. The third stage involved the technical viability of producing concrete blocks, and also the economic viability of some recycling alternatives. As a whole, independently of the strength class, the recycled coarse aggregate blocks fulfilled the required specifications; additionally the economic hypotheses confirmed the viability of producing recycled aggregate units with both production and market costs lower than those of the conventional units. Finally, the fourth stage dealt with the drying shrinkage of mini-walls, the compressive strength and the elasticity modulus of elements (prisms and mini-walls) built with units defined in the former stage. Based on the obtained results, the study showed that only the drying shrinkage property was affected by the recycled aggregates units; the reduction of the distance between two adjacent control joints was an adequate procedure to minimize the effects of the drying shrinkage in this case.

A pesquisa teve como objetivo principal avaliar a incorporação de agregados reciclados de concreto em blocos estruturais de concreto para três classes de resistência (4,5 MPa, 8,0 MPa e 12,0 MPa). O estudo foi desenvolvido basicamente em quatro etapas. A primeira etapa consistiu na análise das propriedades físicas de agregados miúdos e graúdos reciclados de concreto originários de uma fábrica de pré-moldados. Na segunda etapa, foram analisadas as propriedades físicas e mecânicas de corpos-de-prova cilíndricos produzidos com concreto de consistência seca utilizando-se dois tipos de agregados reciclados previamente avaliados. O objetivo foi definir um intervalo de correlação entre a resistência à compressão de corpos-de-prova e blocos, verificar preliminarmente a influência dos agregados reciclados sobre as propriedades físicas e mecânicas e determinar os traços para a próxima etapa. Para a terceira etapa, foi avaliada a viabilidade técnica da produção de blocos com agregados reciclados através da análise de propriedades físicas e mecânicas, sendo também avaliada a viabilidade econômica pela proposição de algumas alternativas para reciclagem. De maneira geral, independentemente do grupo de resistência avaliado, todas as unidades com agregados graúdos reciclados cumpriram os requisitos estabelecidos; já para o estudo econômico, todas as hipóteses atestaram a viabilidade da produção de unidades com agregados reciclados com custos de produção e comercialização inferiores aos das unidades comumente produzidas. Finalmente, a quarta etapa, consistiu na avaliação da retração por secagem em miniparedes, resistência à compressão e módulo de deformação de elementos (prismas e miniparedes) produzidos com as unidades da etapa anterior. Em função dos resultados obtidos, pode-se afirmar que apenas a propriedade de retração por secagem foi afetada pelas unidades com agregados reciclados; nesse caso, a redução da distância entre juntas de controle foi considerada uma medida suficiente para minimizar os efeitos da retração por secagem. / The main goal of the present research project was the evaluation of recycled concrete aggregates incorporation in structural concrete blocks of three different levels of compressive strength (4,5 MPa, 8,0 MPa and 12,0 MPa). The study was developed in four stages. The first stage analyzed the physical properties of fine and coarse concrete aggregates derived from a precast concrete plant. In the second stage, physical and mechanical properties of dry consistency concrete cylindrical specimens were analyzed using two types of recycled aggregates. The aim was to define a correlation interval between the compressive strength of cylindrical specimens and concrete blocks, verify the influence of recycled aggregates on the physical and mechanical properties, and determine the better compositions to be used in the next stage. The third stage involved the technical viability of producing concrete blocks, and also the economic viability of some recycling alternatives. As a whole, independently of the strength class, the recycled coarse aggregate blocks fulfilled the required specifications; additionally the economic hypotheses confirmed the viability of producing recycled aggregate units with both production and market costs lower than those of the conventional units. Finally, the fourth stage dealt with the drying shrinkage of mini-walls, the compressive strength and the elasticity modulus of elements (prisms and mini-walls) built with units defined in the former stage. Based on the obtained results, the study showed that only the drying shrinkage property was affected by the recycled aggregates units; the reduction of the distance between two adjacent control joints was an adequate procedure to minimize the effects of the drying shrinkage in this case.

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.

Les sables issus de la déconstruction du béton (GBR), ontune porosité importante du fait de la présence du mortier résiduel issu du béton primaire. Ceci est un frein à leur recyclage dans le béton, comme cela serait souhaitable dans le cadre d’une économie circulaire de la filière. La carbonatation naturelle par voie aérienne des GBR est connue pour améliorer leurs performances. Par contre elle est très lente et les contraintes de stockage associées ne sont pas acceptables industriellement. Par ailleurs, des bactéries calcifiantes sont utilisées depuis quelques années pour améliorer des sols ou des pierres de monuments. Dans ce contexte, l’objet de cette thèse consiste à développer un procédé de calcification accéléré par dépôt de bactéries à la surface des GBR. La thèse est divisée en 2 phases :- Sélection et adaptation à un pH de 12 de souches bactériennes alcalino-résistantes au cours desquelles leur croissance et leur rendement en CaCO3 ont été évaluées in vitro,en fonction du milieu environnant (pH, présence d’urée, concentration en calcium…) ;- Mise en contact suivant différents procédés avec du sable de béton recyclé (GBR) et des disques de mortier lisses L’efficacité du traitement était évaluée par la diminution de la porosité du matériau A l’issue de ce travail, une souche bactérienne ayant un rendement calcique satisfaisant au contact de GBR a été identifiée. Toutefois la diminution de porosité des GBR traités avec cette bactérie reste limitée. Les observations effectuées montrent que cela est lié à un dépôt hétérogène des produits calciques à la surface des GBR. Des pistes d’amélioration du procédé sont proposées en conclusion du travail. / Sands produced from demolition wastes (RCA) have a significant porosity due to the residual mortar resulting from the primary concrete. This is a brake on their recycling in concrete, as would be desirable to develop the circular economy of the sector. The natural carbonation byair of RCA is known to improve their performance. On the other hand, it is very slow and the associated storage constraints are not industrially acceptable. In addition,calcifying bacteria have been used for years to improve soils or monumental stones. In this context, the object of this thesis is to develop a method of accelerated calcification by deposition of bacteria on the surface of RCA This thesis is divided in 2 phases:- Selection and adaptation to pH12 of alkalophilic bacteria with the study of their growth and theirCaCO3 production yield, in vitro, in different environments (pH, urea or not, calcium concentration…) - RCA and mortar disk treatment with different processes whose efficiency is evaluated by a diminution of the material porosity. At the end of this work, a bacterial strain with a satisfying calcific production in contact with RCA was identified. However, the porosity reduction of the treated RCA porosity remains limited. The observations made show that this is linked to a heterogeneous deposit of calciumproduct on the surface of RCA. To conclude this work,several areas to be explored are proposed to improve the process.

Os resíduos de concreto apresentam grande potencial para serem reciclados quando comparados com outros resíduos, entretanto, o número de estudos realizados no Brasil é muito pequeno dificultando a utilização deste material em dosagens estruturais. Em virtude disso, desenvolveu-se um estudo teórico-experimental visando caracterizar algumas propriedades do agregado e do concreto reciclado; no estudo teórico exploraram-se aspectos relacionados à geração, deposição, processos para recuperação, britagem, casos práticos, pesquisas envolvendo reciclados de concreto e as recomendações normativas existentes. No desenvolvimento experimental, analisou-se a influência do período decorrido entre a moldagem e a reciclagem do concreto nas propriedades dos agregados e concretos. Os resultados indicam que resíduos reciclados logo após sua geração, contribuem positivamente para as propriedades mecânicas do concreto, devido à existência de grande quantidade de partículas não-hidratadas de cimento, tais concretos obtiveram resultados superiores para a resistência à compressão e tração quando comparados aos concretos com agregados naturais. / The concrete residues show a large potential to be recycled when compared with other residues; however, the number of studies in Brazil is very small hindering the use of this material in structural dosage. By virtue of that, it was developed a theoretical-experimental study to characterize some properties of aggregate and recycled concrete; in the theoretical study it was explored aspects related to the generation, deposition, processes for recovery, crushing, practical cases, researches involving recycled of concrete and the existent normative recommendations. In the experimental development, it was analyzed the influence of the period elapsed between the molding and the recycling of the concrete in the properties of the aggregates and concretes. The results indicate that residues recycled soon after generation, these contribute positively to the mechanical properties of the concrete due to the existence of large amount of nonhydrated cement particles, such concretes obtained results superiors for the compression strenght and tensile strenght when compared to the concretes with natural aggregates.

Submitted by Fabricia Fialho Reginato (fabriciar) on 2015-07-08T22:34:01Z No. of bitstreams: 1 DanieleGugel.pdf: 2874038 bytes, checksum: 4386cae5306c5137fce5e8448d48f6fa (MD5) / Made available in DSpace on 2015-07-08T22:34:01Z (GMT). No. of bitstreams: 1 DanieleGugel.pdf: 2874038 bytes, checksum: 4386cae5306c5137fce5e8448d48f6fa (MD5) Previous issue date: 2014-04-02 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / FINEP - Financiadora de Estudos e Projetos / A construção civil é um setor que causa elevado impacto ambiental devido à geração de resíduos e ao elevado consumo de matérias-primas. Demandas cada vez maiores por áreas a serem destinadas a aterros, aliadas à escassez de recursos naturais, favorecem a utilização de resíduos de construção e demolição como fonte para agregados. Neste contexto, muitos estudos estão sendo feitos a respeito de concretos produzidos com resíduos de construção e demolição, focados principalmente nas propriedades mecânicas de resistência à tração e à compressão. Para aplicação como material estrutural, entretanto, a relação tensão x deformação e, particularmente, o Módulo de Elasticidade são importantes parâmetros a serem analisados, pois são diretamente relacionados com o projeto de estruturas. Frente ao exposto, o presente trabalho utilizou agregado graúdo reciclado de concreto (ARC) na confecção de novos concretos e teve como objetivo analisar o comportamento elástico dos mesmos. Para tanto, foram confeccionados concretos com 0% e 50% de substituição de agregados graúdos naturais (AGN) por ARC. O comportamento elástico foi determinado através de um método destrutivo (Estático) e através de um método não destrutivo (Dinâmico) nas idades de 7, 28 e 63 dias para os níveis de carregamento de 0 (somente Dinâmico), 20, 30, 40, 50, 60, 70 e 80% da resistência do concreto. Os resultados encontrados para o Módulo de Elasticidade foram comparados com estimativas a partir de métodos empíricos previstos nas normas CEB-FIP Model Code 1990, ACI 318 (2011) e NBR 6118 (ABNT, 2007 e 2014). Com isso, visou-se observar a influência do ARC nas propriedades elásticas do concreto, comparar o comportamento elástico dos concretos de referência aos resultados dos concretos com ARC, estudar a correlação entre os dois métodos experimentais (Dinâmico e Estático) e verificar a correspondência entre os resultados experimentais obtidos com os normativos. Como principais conclusões, pôde-se verificar que os concretos com ARC apresentam limite elástico similar aos concretos que utilizam somente AGN (este limite situa-se entre 40 e 50% da ƒc); não foi possível identificar uma relação única entre os valores de módulo obtidos pelo Método Dinâmico e pelo Método Estático para ambos os concretos; não é possível afirmar que concretos de resistências similares, mas idades diferentes apresentaram módulos diferentes; os concretos com e sem ARC estudados apresentaram valores de Módulo de Elasticidade obtidos pelo método Estático bastante inferiores aos previstos pelas normas estudadas; os valores de Módulo de Elasticidade obtidos pelo método Dinâmico, para concretos com e sem ARC, estão contidos na faixa entre a norma mais conservadora e a menos conservadora e as curvas obtidas mostram que os concretos com ARC têm comportamento similar aos concretos sem ARC, mas são menos rígidos (maiores deformações para as mesmas tensões). / The construction industry causes a great environmental impact due to the generation of waste and the high consumption of raw material. Increasing demands for areas to become landfills, as well as shortages of natural resources, have favored the use of construction and demolition waste as a source of aggregate. In this context, many studies have been made regarding concretes produced with the use of demolition and construction waste; mainly focused on the mechanical properties of tensile and compressive strength. However, in order to use concretes produced with waste as a structural material, the stress-strain behavior and, particularly, the elastic modulus are important parameters to be analyzed, once they are directly related to structural design. Based on that, the objective of this project is to analyze the elastic behavior of concretes using coarse natural aggregates (NA) and 50% of substitution of these aggregate by coarse recycled concrete aggregates (RCA). The elastic behavior was determined by both a destructive method (static) and a nondestructive one (dynamic) on the ages of 7, 28 and 63 days for the loading levels of 0 (only dynamic), 20, 30, 40, 50, 60, 70 and 80% of respective concrete strength. The found results for the Modulus of Elasticity have been compared to estimates based on the empirical recommendations by CEB-FIP Model Code 1990, ACI 318 (2011) and NBR 6118 (ABNT, 2007 and 2014) standards. The objectives of this work were to observe the influence of the RCA on the elastic properties of concrete; to compare the elastic behavior between concretes with and without RCA, to study the correlation of both experimental methods (dynamic and static) and finally to check the relation between measured and calculated values of modulus of elasticity. The conclusions indicate that concretes with and without RCA have similar elastic limits (between 40% and 50% of the concrete strength); it is not possible to identify a unique relationship between the values obtained by dynamic and static methods for both concretes; it is not possible to assert that concretes with similar strength, but different ages, have different modulus; the values of modulus of elasticity obtained by the static method for both concretes are significantly below that indicated by the considered standards; the values of modulus of elasticity obtained by the dynamic method for concrete with and without RCA are contained in the range between the more and less conservative standards and concretes with RCA have a similar behavior than concretes without RCA, but are less rigid (larger strain for the same stress).

A comparison of concrete containing recycled concrete coarse aggregates and natural coarse aggregates subjected to high strain, low cycle compressive fatigue is presented. Using a strain based feedback control loop, concrete cylinders are compressed at 15µε/s to a specified strain then unloaded to zero stress for 10 cycles. After cycling, all samples are loaded to a strain of 0.008. Direct concrete material variables are the water to cement (w/c) ratio, taken as 0.60, 0.45, and 0.39, and percent coarse recycled concrete aggregate content, varied from zero to 100 percent. The primary testing variable is the specified unloading strain. Unloading strains include 60, 75, 90, 100, and 120 percent of the strain at peak stress. Ten batches of concrete were made, generating a total of 224 samples for testing. Findings confirm previous research showing a reduction in strength with increasing recycled concrete coarse aggregate content, an equivalent concrete with only 25 percent replacement of natural coarse aggregates and an equivalent strength concrete with a decrease in the w/c ratio and 100 percent recycled concrete coarse aggregates. Fatigue testing indicates that each cycle’s maximum stress remains unchanged, but the stiffness degrades more rapidly with increasing recycled aggregate content and a constant w/c ratio.