Os resíduos de construção e demolição (RCD) representam cerca da metade dos resíduos sólidos urbanos. No Brasil, sua geração anual corresponde a aproximadamente 68 milhões de toneladas. Uma forma de se mitigar os impactos ambientais oriundos da disposição desses resíduos sobre o meio ambiente é o seu beneficiamento na forma de agregados reciclados. Os agregados reciclados podem ser classificados em dois grupos, agregados reciclados mistos e agregados reciclados de concreto (ARC). Entre as diversas formas de aplicação dos agregados reciclados, destaca-se a construção rodoviária por utilizar quantidade expressiva tanto de materiais graúdos, quanto de miúdos. No Brasil, ainda existem poucos relatos científicos sobre o desempenho de agregados reciclados de concreto em camadas de pavimentos. Assim, o objetivo desta pesquisa é estudar as propriedades físicas e o comportamento mecânico, através da análise de resultados de ensaios laboratoriais, do agregado reciclado de concreto proveniente da Usina de Reciclagem de Resíduos da Construção Civil de São Carlos-SP, visando seu emprego em camadas de base e sub-base de pavimentos. Foram realizados ensaios de caracterização física, lixiviação, solubilização, compactação, Índice de Suporte Califórnia (CBR), compressão simples, compressão diametral e triaxial cíclico. A título de comparação, foram pesquisados, também, um agregado natural, um solo de comportamento laterítico e uma mistura deste solo com o agregado reciclado de concreto. Observou-se que o ARC apresentou um comportamento mecânico muito próximo ao do agregado natural, material convencionalmente utilizado em camadas de pavimento na região. Destaca-se ainda que o agregado reciclado de concreto apresentou um ganho considerável de resistência e rigidez com o decorrer do tempo de cura. No tocante à energia de compactação, este parâmetro teve influência significativa sobre o comportamento do ARC para os tempos iniciais de cura, sendo que para os maiores períodos de cura, essa influência diminuiu. Finalmente, com base na avaliação dos resultados obtidos nesta pesquisa, concluiu-se que o agregado reciclado de concreto pode ser empregado na construção de camadas de sub-base e base de pavimentos. / The construction and demolition wastes (C&D) represent about half of municipal solid wastes. There are estimative that, In Brazil, are produced approximately 68 million tons annually. One way to reduce the environmental impacts caused by theirs disposal is processing to obtain recycled aggregates. The recycled aggregate can be classified into two groups according their composition: mixed recycled aggregates and recycled concrete aggregates (RCA). Among different forms of application, roadway construction deserves prominence because of its singular characteristic to use considerable amounts or materials. In Brazil, there are few researches about behavior of recycled concrete aggregate in pavement layers. Thus, the objective of this research is to study the physical and mechanical behavior of recycled concrete aggregate (RCA) from São Carlos - SP, in order to investigate its utilization in base and subbase pavements layers. The laboratorial tests included in this research were physical characterization, leaching, dissolution, moisture-density relationships, California Bearing Ration (CBR), unconfined compressive strength, diametral compression and cyclic loading triaxial tests. Even, tests were conducted to compare the behavior of a natural aggregate, a lateritic soil and a mixture of this soil with the recycled concrete aggregate. It was observed that the RCA had similar mechanical behavior when compared to natural aggregate, material usually used in pavements layers of highways around São Carlos. Besides, the recycled concrete aggregate showed a considerable gain in strength and stiffness over time. About the energy compaction, this parameter had significant influence on RCA behavior for initial curing and decreased for the more periods of curing. Finally, based on evaluation of research results it was concluded that the RCA can be used in construction of base and subbase of pavements layers.

Virgin aggregate is being used faster than it is being made available creating a foreseeable shortage in the future. Despite this trend, the availability of demolished concrete for use as recycled concrete aggregate (RCA) is increasing. Using this waste concrete as RCA conserves virgin aggregate, reduces the impact on landfills, decreases energy consumption and can provide cost savings. However, there are still many unanswered questions on the beneficial use of RCA in concrete pavements. This research addresses the many technical and cost-effective concerns regarding the use of RCA in concrete pavements by identifying concrete mixture and proportioning designs suitable for jointed plain concrete pavements; constructing test sections using varying amounts of RCA; monitoring performance through testing, condition surveys and sensor data; modeling RCA pavement performance; and predicting life cycle costs. The research was carried out as a partnership between the Centre for Pavement and Transportation Technology (CPATT) at the University of Waterloo, the Cement Association of Canada, Dufferin Construction, and the Natural Sciences and Engineering Research Council of Canada. The literature review provides an overview of sustainability and key performance indicators, the material properties of RCA both as an aggregate and in concrete, concrete mixture and proportioning designs with RCA, performance of existing RCA pavements, and the implementation of RCA highlighting some examples where RCA has been used successfully. Twelve preliminary mixes were developed using three total cementitious contents amounts of 315 kg/m3, 330 kg/m3, and 345 kg/m3 to determine four suitable mixes with varying coarse RCA contents (0%, 15%, 30% and 50%) to place at the CPATT test track. At 28-days, all of the twelve mixes exceed the 30 MPa design strength. Four test sections containing 0%, 15%, 30% and 50% coarse RCA were constructed in June 2007. The test sections had identical cross sections consisting of 250 mm portland cement concrete (PCC), 100 mm asphalt-stabilized OGDL and a 450 mm granular base. For each coarse RCA content, one slab was instrumented with six vibrating wire concrete embedment strain gages to measure long-term longitudinal and transverse strain due to environmental changes, two vibrating wire vertical extensometers to monitor slab curling and warping, two vibrating wire inter-panel extensometers to monitor joint movement, and two maturity meters to measure maturity and temperature. Quality assurance and quality control (QA/QC) testing showed that the mixes containing RCA exhibited similar or improved performance when compared to the conventional concrete for compressive and flexural strength, freeze-thaw durability and coefficient of thermal expansion. Pavement performance of the four test sections was evaluated using visual surveys following the Ontario Ministry of Transportation’s Manual for Condition rating of Rigid Pavements. Nine pavement evaluations have been performed every two to four months since construction. All test sections are in excellent condition with pavement condition index (PCI) values greater than 85 after two years in-service and approximately three hundred thousand Equivalent Single Axle Loads. Sensor data from the strain gauges, and vertical and inter-panel extensometers are providing consistent results between the test sections. Long-term performance modeling using the Mechanistic-Empirical Pavement Design Guide (ME-PDG) showed improved performance with respect to cracked slabs, joint faulting, and pavement roughness as the RCA content increased. Multivariable sensitivity analysis showed that the performance results were sensitive to CTE, unit weight, joint spacing, edge support, surface absorption, and dowel bar diameter. Life cycle cost analysis (LCCA) illustrated the savings that can be expected using RCA as a replacement aggregate source as the cost of virgin aggregate increase as the sources becomes depleted. Multivariable sensitivity analysis showed that the LCCA results were sensitive to construction costs, discount rate, and maintenance and rehabilitation quantities.

Virgin aggregate is being used faster than it is being made available creating a foreseeable shortage in the future. Despite this trend, the availability of demolished concrete for use as recycled concrete aggregate (RCA) is increasing. Using this waste concrete as RCA conserves virgin aggregate, reduces the impact on landfills, decreases energy consumption and can provide cost savings. However, there are still many unanswered questions on the beneficial use of RCA in concrete pavements. This research addresses the many technical and cost-effective concerns regarding the use of RCA in concrete pavements by identifying concrete mixture and proportioning designs suitable for jointed plain concrete pavements; constructing test sections using varying amounts of RCA; monitoring performance through testing, condition surveys and sensor data; modeling RCA pavement performance; and predicting life cycle costs. The research was carried out as a partnership between the Centre for Pavement and Transportation Technology (CPATT) at the University of Waterloo, the Cement Association of Canada, Dufferin Construction, and the Natural Sciences and Engineering Research Council of Canada. The literature review provides an overview of sustainability and key performance indicators, the material properties of RCA both as an aggregate and in concrete, concrete mixture and proportioning designs with RCA, performance of existing RCA pavements, and the implementation of RCA highlighting some examples where RCA has been used successfully. Twelve preliminary mixes were developed using three total cementitious contents amounts of 315 kg/m3, 330 kg/m3, and 345 kg/m3 to determine four suitable mixes with varying coarse RCA contents (0%, 15%, 30% and 50%) to place at the CPATT test track. At 28-days, all of the twelve mixes exceed the 30 MPa design strength. Four test sections containing 0%, 15%, 30% and 50% coarse RCA were constructed in June 2007. The test sections had identical cross sections consisting of 250 mm portland cement concrete (PCC), 100 mm asphalt-stabilized OGDL and a 450 mm granular base. For each coarse RCA content, one slab was instrumented with six vibrating wire concrete embedment strain gages to measure long-term longitudinal and transverse strain due to environmental changes, two vibrating wire vertical extensometers to monitor slab curling and warping, two vibrating wire inter-panel extensometers to monitor joint movement, and two maturity meters to measure maturity and temperature. Quality assurance and quality control (QA/QC) testing showed that the mixes containing RCA exhibited similar or improved performance when compared to the conventional concrete for compressive and flexural strength, freeze-thaw durability and coefficient of thermal expansion. Pavement performance of the four test sections was evaluated using visual surveys following the Ontario Ministry of Transportation’s Manual for Condition rating of Rigid Pavements. Nine pavement evaluations have been performed every two to four months since construction. All test sections are in excellent condition with pavement condition index (PCI) values greater than 85 after two years in-service and approximately three hundred thousand Equivalent Single Axle Loads. Sensor data from the strain gauges, and vertical and inter-panel extensometers are providing consistent results between the test sections. Long-term performance modeling using the Mechanistic-Empirical Pavement Design Guide (ME-PDG) showed improved performance with respect to cracked slabs, joint faulting, and pavement roughness as the RCA content increased. Multivariable sensitivity analysis showed that the performance results were sensitive to CTE, unit weight, joint spacing, edge support, surface absorption, and dowel bar diameter. Life cycle cost analysis (LCCA) illustrated the savings that can be expected using RCA as a replacement aggregate source as the cost of virgin aggregate increase as the sources becomes depleted. Multivariable sensitivity analysis showed that the LCCA results were sensitive to construction costs, discount rate, and maintenance and rehabilitation quantities.

Using recycled concrete aggregate (RCA) as a replacement for natural aggregate in new concrete is a promising way to increase the overall sustainability of new concrete. This has been hindered, however, by a general perception that RCA is a sub-standard material due to the lack of technical guidance, specifically related to long-term durability, on incorporating RCA into new concrete. The goal of this research project was to determine whether current testing methods could be used to assess the potential alkali-silica reactivity of concrete incorporating RCA. The test methods investigated were ASTM C1260 and ASTM C1567 for assessing natural aggregate susceptibility to alkali-silica reactivity (ASR), and the ability of supplementary cementitious materials (SCMs) to mitigate ASR, respectively. Seven different RCA sources were investigated. It was determined that ASTM C1260 was effective in detecting reactivity but expansion varied based on RCA processing. Depending on the aggregate type and the extent of processing, up to a 100% increase in expansion was observed. Replicate testing was performed at four university laboratories to evaluate repeatability and consistency of results. The authors recommend modification to the mixing and aggregate preparation procedures, when testing the reactivity of RCA using ASTM C 1260. This study also investigated the efficacy of replacing portland cement with supplementary cementitious materials (SCMs), known to mitigate alkali-silica reaction (ASR) in concrete with virgin aggregates, to control ASR in concrete incorporating reactive RCA. The SCMs investigated as part of this study included: fly ash (class F), silica fume, and metakaolin. The results of modified alkali-silica reactivity tests, ASTM C1260 and ASTM C1567 (AMBT), are presented for two different recycled concrete aggregates when using 100% portland cement, binary blends of portland cement and fly ash, and ternary blends of portland cement, fly ash and metakaolin or silica fume. The results indicate that SCMs can effectively mitigate ASR in concrete made with RCA. A 40% replacement of portland cement with class F fly ash was able to reduce expansions to below 0.10% in the AMBT for concrete containing 100% of a highly reactive recycled concrete aggregate. A ternary blend, however, of portland cement with a class F fly ash and metakaolin was most effective for both RCAs tested in this study. Higher levels of mitigation may be required for some RCAs, compared to the level required to mitigate ASR in concrete made with their original natural aggregates, depending on the age and composition of the RCA. / Graduation date: 2012

Dans une démarche de valorisation des déchets, les granulats recyclés sont introduits dans la formulation des bétons pour donner naissance à de nouveaux bétons recyclés qui représentent l’objet du projet national RECYBETON et du projet ANR ECOREB. Cette thèse se concentre sur l’étude du béton frais et en particulier la maîtrise du retrait plastique et l’effet du degré de saturation initial des gravillons recyclés sur le comportement des bétons recyclés. Deux familles de bétons avec des rapports eau/ciment respectifs de 0,6 et 0,45 ont été testés en conditions endogènes ainsi qu’en dessiccation (Vvent = 8 m/s). Chaque famille de bétons est constituée d’un béton naturel de référence et de deux bétons recyclés différenciés pas le degré initial de saturation des gravillons recyclés (50 et 120 % de l’absorption nominale). Les résultats expérimentaux soulignent la capacité des gravillons recyclés initialement partiellement saturés à capter rapidement l’eau contenue dans la pâte de ciment, modifiant ainsi le rapport E/C, les propriétés rhéologiques du béton frais et les résistances mécaniques du béton durci. Après saturation en eau, si les conditions de séchage conduisent à un manque d’eau dans le béton, les gravillons recyclés peuvent fournir de l’eau à la pâte. Ils constituent donc un potentiel de cure interne. Le retrait plastique sous vent est explicitement lié au ressuage, au développement de la pression capillaire et à la fissuration. Le temps d’initiation de la fissuration dépend de la quantité d’eau totale dans le béton et de sa capacité à ressuer tandis que l’ouverture de fissure varie avec la valeur de retrait plastique mesurée. Dans cette étude, le développement de la pression capillaire est la cause de la fissuration qui apparaît dès l’entrée d’air dans le matériau poreux. Les différences de comportements les plus importantes sont observées entre bétons ayant une quantité d’eau totale différente plutôt qu’entre bétons naturel et recyclé. La compilation des résultats expérimentaux a permis de mettre sur pied des modélisations qui illustrent les comportements observés. Les pores concernés par l’entrée d’air dans les bétons recyclés et naturels au moment de la fissuration sont les plus gros pores de la pâte. Enfin, un couplage hygrothermique séchage-température du béton peut influer sur le démarrage de l’hydratation. / In the context of sustainable development, the reuse of construction and demolition waste is necessary to conserve nonrenewable natural aggregate resources, so recycled aggregates are introduced in concrete mix design. This is the aim of the national projet RECYBETON and the research project ECOREB. This study deals with the fresh concrete and more specifically with shrinkage control and the effects of the initial saturation degrees of recycled coarse aggregates on concrete behavior.Two concrete families, with two different water/cement ratios 0,60 and 0,45, are tested under endogenous and drying (wind speed equal to 8 m/s) conditions. Each concrete family contains a reference natural concrete and two recycled concretes. The initial saturation degree is the difference between them (recycled coarse aggregates saturated or semi saturated).Experimental results underline the capacity of non-saturated aggregates to quickly absorb water from cement paste, modifying the W/C ratio, rheological properties of the fresh concrete and the mechanical strength (at 28 days) of recycled concretes. After saturation in water, recycled aggregates can release water into the cement paste if the undergone drying conditions lead to a lack of water in the cement matrix. The recycled coarse aggregates can be seen as an internal curing potential.Experimental plastic shrinkage studies carried out under drying conditions highlight a link between bleeding, capillary pressure, plastic shrinkage and cracking. It should be pointed out that the initial cracking is dependent on the total quantity of water in the concrete and on its bleeding capacity. The opening cracks vary with the plastic shrinkage values measured during the test. The analysis of the results emphasize that the capillary pressure is the determining parameter and that the air entry value matches the cracks. The major behavior differences are found between concretes with different volumes of water rather than between natural and recycled concretes.Finally, the analysis of all the experimental results have allowed concrete modelling and understanding why concretes do not behave in the same way. When it cracks, the air come in the biggest pores of the concrete paste. Moreover, a hygrothermal coupling exists between the drying and the temperature in concrete. It can affect hydration start up.

En la actualidad en gran parte del mundo se viene proponiendo e impulsando las políticas ambientales que puedan reducir el problema de la degradación de los recursos naturales a la que está siendo sometido el planeta. A tal efecto se plantea la realización de esta investigación para tratar de determinar el grado de influencia en las propiedades físicas del concreto fabricado con agregados reciclados procedentes de la trituración. La variable seleccionada para la investigación ha sido: el porcentaje de sustitución del agregado grueso natural por agregado grueso reciclado en la dosificación del concreto. El objetivo general de la investigación es analizar en qué medida la cantidad de agregado grueso reciclado usado en la dosificación de la mezcla influye en las propiedades mecánicas del concreto. El tipo de investigación fue básica y cualitativa, la metodología. Se usó una metodología experimental y transversal. El análisis de los resultados experimentales indican que la resistencia a la compresión y a la tracción no se ven afectadas notoriamente al reemplazar el 20% de agregado natural, en un mayor porcentaje de reemplazo , la resistencia empieza a decaer directamente proporcional a un mayor porcentaje de agregado reciclado. Today in much of the world has been proposing and promoting environmental policies that can reduce the problem of the degradation of natural resources that the planet is undergoing. For this purpose the realization of this research to try to determine the degree of influence on the physical properties of concrete made with recycled aggregate from crushing arises. The selected research variable was the percentage of coarse natural aggregate replacement by recycled coarse aggregate concrete proportions. The overall objective of the research is to analyze to what extent the amount of recycled coarse aggregate used in the dosage of the mixture influences the mechanical properties of concrete. The research was basic and qualitative methodology. An experimental and transversal approach was used. Analysis of the experimental results indicate that the compressive strength and tensile strength are not affected noticeably by replacing 20% of natural aggregate, a higher percentage replacement, resistance begins to drop directly proportional to a higher percentage of added recycling.

Os resíduos de construção e demolição (RCD) representam cerca da metade dos resíduos sólidos urbanos. No Brasil, sua geração anual corresponde a aproximadamente 68 milhões de toneladas. Uma forma de se mitigar os impactos ambientais oriundos da disposição desses resíduos sobre o meio ambiente é o seu beneficiamento na forma de agregados reciclados. Os agregados reciclados podem ser classificados em dois grupos, agregados reciclados mistos e agregados reciclados de concreto (ARC). Entre as diversas formas de aplicação dos agregados reciclados, destaca-se a construção rodoviária por utilizar quantidade expressiva tanto de materiais graúdos, quanto de miúdos. No Brasil, ainda existem poucos relatos científicos sobre o desempenho de agregados reciclados de concreto em camadas de pavimentos. Assim, o objetivo desta pesquisa é estudar as propriedades físicas e o comportamento mecânico, através da análise de resultados de ensaios laboratoriais, do agregado reciclado de concreto proveniente da Usina de Reciclagem de Resíduos da Construção Civil de São Carlos-SP, visando seu emprego em camadas de base e sub-base de pavimentos. Foram realizados ensaios de caracterização física, lixiviação, solubilização, compactação, Índice de Suporte Califórnia (CBR), compressão simples, compressão diametral e triaxial cíclico. A título de comparação, foram pesquisados, também, um agregado natural, um solo de comportamento laterítico e uma mistura deste solo com o agregado reciclado de concreto. Observou-se que o ARC apresentou um comportamento mecânico muito próximo ao do agregado natural, material convencionalmente utilizado em camadas de pavimento na região. Destaca-se ainda que o agregado reciclado de concreto apresentou um ganho considerável de resistência e rigidez com o decorrer do tempo de cura. No tocante à energia de compactação, este parâmetro teve influência significativa sobre o comportamento do ARC para os tempos iniciais de cura, sendo que para os maiores períodos de cura, essa influência diminuiu. Finalmente, com base na avaliação dos resultados obtidos nesta pesquisa, concluiu-se que o agregado reciclado de concreto pode ser empregado na construção de camadas de sub-base e base de pavimentos. / The construction and demolition wastes (C&D) represent about half of municipal solid wastes. There are estimative that, In Brazil, are produced approximately 68 million tons annually. One way to reduce the environmental impacts caused by theirs disposal is processing to obtain recycled aggregates. The recycled aggregate can be classified into two groups according their composition: mixed recycled aggregates and recycled concrete aggregates (RCA). Among different forms of application, roadway construction deserves prominence because of its singular characteristic to use considerable amounts or materials. In Brazil, there are few researches about behavior of recycled concrete aggregate in pavement layers. Thus, the objective of this research is to study the physical and mechanical behavior of recycled concrete aggregate (RCA) from São Carlos - SP, in order to investigate its utilization in base and subbase pavements layers. The laboratorial tests included in this research were physical characterization, leaching, dissolution, moisture-density relationships, California Bearing Ration (CBR), unconfined compressive strength, diametral compression and cyclic loading triaxial tests. Even, tests were conducted to compare the behavior of a natural aggregate, a lateritic soil and a mixture of this soil with the recycled concrete aggregate. It was observed that the RCA had similar mechanical behavior when compared to natural aggregate, material usually used in pavements layers of highways around São Carlos. Besides, the recycled concrete aggregate showed a considerable gain in strength and stiffness over time. About the energy compaction, this parameter had significant influence on RCA behavior for initial curing and decreased for the more periods of curing. Finally, based on evaluation of research results it was concluded that the RCA can be used in construction of base and subbase of pavements layers.

En los últimos años existe una demanda cada vez más creciente de infraestructura; actualmente en el Perú el sector construcción ha ido en constante crecimiento; sin embargo, es uno de los más contaminantes debido a la fabricación del concreto y sus componentes, ya que la industria concretera es responsable de la extracción de recursos no renovables; siendo el concreto el material fundamental para los diferentes tipos de proyectos en vías de desarrollo. Frente a este entorno, se propone como alternativa sostenible el uso de residuos de demolición, es decir agregado grueso de concreto reciclado en reemplazo del agregado grueso natural; sin embargo, en investigaciones anteriores el reemplazo de este, presenta una disminución en la resistencia a la compresión y flexión de 10% - 25% y 23.7% respectivamente. Por esta razón, se seleccionó el vidrio triturado proveniente del reciclado de botellas incoloras, este es un material eco amigable y de características que contribuyen en la resistencia del concreto. En consecuencia, se propone el uso de estos agregados reciclados en reemplazo total y parcial del agregado grueso y fino respectivamente. Los resultados de estos ensayos indicaron un aumento en las propiedades mecanicas del concreto y el porcentaje óptimo de reemplazo de vidrio triturado es 20%, en donde se obtuvo un incremento de 12.33% en la Resistencia a la compresión, 17.19% en la Resistencia a la flexion y 1.98% en la Resistencia a la tracción. / In recent years there is an increasingly growing demand for infrastructure; Currently in Peru the construction sector has been in constant growth; However, it is one of the most polluting due to the manufacture of concrete and its components, since the concrete industry is responsible for the extraction of non-renewable resources; concrete being the fundamental material for the different types of projects under development. Faced with this environment, the use of demolition waste is proposed as a sustainable alternative, that is, coarse aggregate of recycled concrete to replace the natural coarse aggregate; However, in previous research, its replacement shows a decrease in compressive and flexural strength of 10% -25% and 23.7%, respectively. For this reason, the crushed glass from the recycling of colorless bottles was selected since it is an eco-friendly material and features that contribute to the strength of the concrete. Consequently, the use of these recycled aggregates is proposed in total and partial replacement of the coarse and fine aggregate respectively. The results of these tests indicated an increase in the mechanical properties of the concrete and the optimum percentage of replacement of crushed glass is 20%, where an increase of 12.33% in Compressive Strength, 17.19% in Resistance to Compression was obtained. flexion and 1.98% in tensile strength. / Tesis

En este artículo se analiza la influencia de un aditivo a base de nanosilice en el concreto elaborado con agregado a partir de concreto reciclado. Para lo cual, se ha realizado un programa de laboratorio donde se analizan las propiedades físicas de los materiales y las propiedades en estado fresco y endurecido del concreto a distintas edades. El objetivo principal del estudio es demostrar las mejoras cuantitativas de resistencia a compresión y tracción del concreto con ACR empleando nanosilice. Asimismo, el diseño óptimo para los casos propuestos es la mezcla M4 (100% ACR y 1% nanosilice) con el cual se logra mejorar en 21% respecto a la muestra M3 (100% ACR) a 28 días. Finalmente, el diseño M4 tiene una mayor resistencia a compresión comparado con la mezcla M0 (1) concreto convencional sin nanosilice. Por consiguiente, la utilización del concreto con ACR es factible en términos de resistencia. / This article discusses the influence of a nanosilize based admixture on concrete made with aggregate from recycled concrete. For which, a laboratory program has been carried out where the physical properties of the materials and the properties in the fresh and hardened state of concrete at different ages are analyzed. The main objective of the study is to demonstrate the quantitative improvements of resistance to compression and tension of concrete with ACR using nanosilice. Likewise, the optimal design for the proposed cases is the M4 mixture (100% ACR and 1% nanosilize) with which it is possible to improve by 21% compared to the M3 sample (100% ACR) at 28 days. Finally, the M4 design has a higher compressive strength compared to the conventional concrete mix M0 (1) without nanosilize. Therefore, the use of concrete with ACR is feasible in terms of strength. / Tesis

Det pågår just nu ett arbete inom byggindustrin att allt mer gå över till en cirkulär ekonomi för att hushålla på världens naturliga resurser. För betongtillverkningen innebär det att försöka ersätta naturballast med återvunnen betong som ballast. Men för tillfället finns det lagkrav som förhindrar att naturballast helt ska kunna ersättas av återvunnen betong som ballast. Det är för att det finns vissa fysikaliska egenskaper, så som att porositeten ökar, som gör att de mekaniska egenskaperna blir sämre när naturballast ersätts med återvunnen betong som ballast. Detta examensarbete utfördes genom experimentella studier. Undersökningen utfördes i mekanik- och betonglaboratorium på Högskolan i Borås. Det utfördes en storskalig gjutningsserie där betongavfall från Ulricehamns Betong AB (UBAB) och Hedareds Sand & Betong AB (HEDA) prövades som ballastersättare till 50 och 100 %. För samtliga försök uppmättes både sättmått och betongens mekaniska egenskaper. Resultaten från betong med återvunnen betong som ballast (RAC) jämfördes med referensbetongen. Referensbetongen är baserad på ett känt- och beprövat originalrecept från UBAB respektive HEDA. Betongen med återvunnen betong som ballast är baserad på modifieringar som gjorts på referensrecept. Målet med studien var att undersöka hur återvunnen betong som ballast i betongblandningen påverkar betongens mekaniska egenskaper så som tryckhållfasthet, spräckhållfasthet och elasticitetsmodul. De testerna utfördes på gjutna cylindrar efter 28 dygn, tryckhållfastheten var också testad efter 7 dygn. Böjdraghållfasthet testades på balkar efter 28 dagar. Sedan utvärderades dessa resultat för att se hur de mekaniska egenskaperna förändras när en större del återvunnen betong som ballast används i recepten. Resultaten varierar litegrann för de olika provningarna. Denna studie styrker tesen att minskningen av tryckhållfastheten, efter 28 dagars härdning, som sker när återvunnen betong som ballast (RCA) används är inom intervallet 5–24 %. Provningarna av elasticitetsmodulen uppvisar liknande tendenser som tidigare forskning då betongen blir lite mindre styv när naturballast (NA) ersätts av RCA. Den styrker även tidigare forskning där böjdraghållfastheten är större vid ökade RCA-mängder. Då det för HEDA-recepten uppvisades en ökning med 9 procentenheter när all NA ersattes med RCA. Spräckhållfastheten uppvisade samma tendenser som böjdraghållfastheten. Det resultatet är däremot inte i linje med vad som har visats i tidigare forskning, då spräckhållfastheten har i de studierna minskat vid högre ersättningsandelar. / Work in the construction industry is currently underway to move to a circular economy to preserve the world’s natural resources. For concrete production this means trying to replace natural aggregate with recycled concrete aggregate. But for the time being there are standard allows that prevent natural aggregate from being completely replaced by recycled concrete aggregate. This is because there are certain physical properties, such as an increase in porosity, which have a negative impact on the mechanical properties when natural aggregate is replaced with recycled concrete aggregate. This thesis is carried out through experimental studies. The study was carried out in the mechanical and concrete laboratory at the University of Borås. Large scale castings were done where concrete waste from Ulricehamns Betong AB (UBAB) and Hedareds Sand & Betong AB (HEDA) were tested as aggregate replacers. For all experiments, both the measurement dimensions and the mechanical properties of the concrete was measured. The results from the recycled aggregate concrete were compared with the reference concrete. The reference concrete is based on an industrially active recipe from UBAB and HEDA. The Recycled Aggregate Concrete (RAC) is based on modifications made on reference recipes. The aim of this study was to investigate how recycled concrete aggregate in the concrete mix affects the mechanical properties of the concrete, such as compressive strength, splitting tensile strength and the modulus of elasticity. They were performed on cylinders at 28 days, the compressive strength was also performed at 7 days. The flexural strength was also tested. Those tests were performed on beams. Then these results were evaluated to see how the mechanical properties change when a greater replacement ratio is used in the recipes. The results vary slightly for the different tests. This study confirms that the decrease in compressive strength, after 28 days hardening, that occurs when Recycled Concrete Aggregate (RCA) is used is within the range 5–24%. The tests of the modulus of elasticity show similar tendencies as previous research because the concrete becomes a little less stiff when Natural Aggregate (NA) is replaced by RCA. It also corroborates previous research where the flexural strength is greater with increased RCA amounts. When the HEDA prescriptions showed an increase of 9 percentage when all NA was replaced with RCA. The splitting tensile strength exhibited the same tendencies as the flexural strength. On the other hand, this result is not in line with what has been shown in previous research, as the splitting tensile strength in those studies has decreased at higher replacement ratios.