Recycled concrete is among the rising eco-friendly construction materials which helps to reduce waste and the need for new natural resources. However, such concrete may present previous deterioration due to, for instance, alkali-silica reaction (ASR), which is an ongoing distress mechanism that may keep being developed in the recycled material. This work aims to evaluate the potential of further distress and crack development (i.e. initiation and propagation) of AAR-affected RCA concrete in recycled mixtures displaying distinct past damage degrees and reactive aggregate types. Therefore, concrete specimens incorporating two highly reactive aggregates (Springhill coarse aggregate and Texas sand) were manufactured in the laboratory and stored in conditions enabling ASR development. The specimens were continuously monitored over time and once they reached marginal (0.05%) and very high (0.30%) expansion levels, they were crushed into RCA particles and re-used to fabricate RCA concrete. The RCA specimens were then placed in the same previous conditions and the “secondary” ASR-induced development monitored over time. Results show that the overall damage in ASR-affected RCA concrete is quite different from affected conventional concrete, especially with regards to the severely damaged RCA particles, where ASR is induced by a reactive coarse aggregate, as the RCA particle itself may present several levels of damage simultaneously caused by past/ongoing ASR and newly formed ASR. Moreover, the influence of the original damage extent in such RCA concrete was captured by the slightly damaged RCA mixture eventually reaching the same damage level as the severely damaged mixture. Furthermore, the original extent of deterioration influence the “secondary” induced expansion and damage of RCA concrete since the higher the original damage level, the higher the cracks numbers and lengths observed in the RCA concrete for the same expansion level whereas wider cracks are generated by RCA having previously been subjected to slight damage thus indicating the difference in the distress mechanism as a function of original extent of damage. In addition, it has been found that distress on RCA containing a reactive sand generates and propagates from the residual mortar (RM) into the new mortar (NM) as opposed to RCA containing a reactive coarse aggregate, being generated and propagated from the original coarse aggregate (i.e. original virgin aggregate – OVA) into the NM. Likewise, RCA containing a reactive sand caused longer and higher number of cracks for the same “secondary” induced expansion than the RCA made of reactive coarse aggregate. Finally, novel qualitative and descriptive models are proposed in this research to explain ASR-induced distress generation and propagation on RCA mixtures made of reactive fine and coarse aggregates.

Afin de répondre aux questions des propriétaires de structures atteintes de réaction alcali-silice (RAS), ce travail se concentre sur une partie d'une méthodologie globale, proposée initialement par le LMDC et EDF, et dont le but est l'étude du comportement mécanique des constructions endommagées par la RAS. Pour atteindre cet objectif, l'avancement chimique de la RAS des granulats récupérés dans les structures affectées doit être évalué. Ainsi, ce travail est consacré à la quantification de la silice potentiellement réactive des granulats, par l'utilisation de deux approches : une approche indirecte par un test d'expansion et une approche directe par des méthodes chimiques. La présentation du manuscrit s'articule autour des points suivants :• Un test d'expansion pertinent et rapide sur mortiers pour relier la quantité de silice réactive à l'expansion mesurée. Les conditions expérimentales suivantes ont été choisies pour tester différentes tailles et natures de granulats, ainsi que différentes tailles d'éprouvettes : solution de NaOH à 1 mol/l et température de conservation de 60°C.• Une méthode chimique rapide de dissolution sélective pour mesurer directement la quantité de silice réactive disponible pour la RAS. La méthode HF / HF+HCl a été trouvé comme étant la plus efficace.• Un modèle chemo-mécanique pour analyser les effets de la taille des granulats et des éprouvettes, et évaluer l'avancement chimique de la réaction.Finalement, une méthodologie est proposée pour calculer la constante cinétique de la réaction dans le cadre de la requalification des structures atteintes de RAS. / In order to answer the questions of the ASR-affected structures owners, this work focused on a part of a global methodology, which is proposed originally by the LMDC and EDF, aiming to reassess the mechanical behavior of ASR-damaged constructions. To achieve this purpose, the chemical advancement of ASR in the aggregates recovered from the structure should be evaluated. Thus, this work focuses on the assessment of the potentially reactive silica content with two main methods: indirectly by expansion test and directly by chemical methods. The presentation of this manuscript is around the following points: • A relevant and rapid expansion test on mortars to link the reactive silica content to measured expansion. The experimental condition: 1 mol/l NaOH solution conserved at 60°C is chosen to test different aggregate sizes, specimen sizes and natures of aggregate. • A fast chemical method of selective dissolution to measure directly the silica available for ASR. Acid/basic methods are tested and compared; HF / HF+HCl method is found to be the most effective. • A chemo-mechanical model to analyze the effect of aggregate size and specimen size, and evaluate the chemical advancement of ASR. Finally, a methodology is proposed to calculate the kinetics constant in the framework of structural requalification. Key words: alkali-silica reaction (ASR), chemical advancement, reactive silica, expansion test, chemical test, chemo-mechanical model, kinetic constant, selective dissolution

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Natural rice husk ash (RHA) used in concrete contributes to civil construction sustainability. In fact, RHA is considered a residual pollutant and then it is necessary to destine this material correctly. However, it is necessary to investigate the consequences of replacing part of cement by natural RHA to produce concrete for structural purposes. In this context, the aim of this study was to evaluate the concrete durability produced with 15 % of blinder partial replacement by natural RHA in the expansion due to alkali-silica reaction (ASR) and penetration of chloride ion, as well as to suggest preventive measures with the use of mineral additions. In the present study, natural RHA was used as partially replacement of Portland cement. This natural RHA has been obtained without temperature control burning and placed directly into the mixer to suffer self-grinding with aggregates. We investigated the RAS neutralization of natural RHA by the use of cement with mineral additions (CPIIZ, CPIII e CPIV), as well as, we performed additional replacements of part from CPIIZ cement by fly ash (10, 15, 20, 30 and 40 %). We employed accelerated expansion method at 80°C in mortar bars followed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and long term at 38 °C and accelerated at 60 °C methods in concrete prisms. To investigate concrete resistance in the chloride ion penetration, we used chloride ions penetration method by immersion in saline solution (CPT) of concrete produced with natural RHA and CPIIZ cement added of fly ash (0, 12.75 or 17 %) and water-binder ratios of 0.45, 0.55 and 0.65 were adopted. Analyses of results were based in slope (K ) obtained from the average depths of penetration. In this study, we verified that in mortar bars assay the natural RHA generated expansion above of results allowed by norm in mixtures with standard cement, while CPIIZ cement with addition from 20 % of fly ash showed to mitigate the ASR. These results demonstrated that effect of mitigation of RAS proportionally increased with fly ash addition. Moreover, CPIV cement demonstrated excellence in mitigate the expansive reaction. The SEM analysis identified the characteristic products of ASR in the samples containing natural RHA. XRD analysis showed that the samples of mixtures with higher content of mineral addition showed peaks of calcium hydroxide (CH) with less intensity and mixtures with natural RHA presented greater calcium carbonate content. In relation to concrete prisms molded at 60°C, results showed an increase in expansion for mixture of CPIIZ with natural RHA, but these results remained below of maximum expansion predicted by test. Mixtures of CPII-Z with natural RHA added of 10 and 15% fly ash demonstrated better efficiency in expansion mitigation. In relation to concrete prisms molded at 38°C, the results are not conclusive to 12 months, but mixtures that presented a great expansion were of CPII-Z with natural RHA and 15% fly ash, the CPII-Z with RHA natural and CPII-Z with natural RHA and 10% fly ash, respectively. However, all mixtures had expansion below the maximum limit suggested by the Brazilian standard at 24 months. Through of results CPT, we can conclude that mineral additions provided improvements to the concrete with higher ages due to pozzolanic effect. Moreover, the best results obtained were in trace with lowest water-binder ratios, probably due to increased consumption of cement, which increases the CH amount to interact with the RHA and the fly ash. Therefore, mixtures of Portland cement with fly ash and natural RHA meet the durability of concrete, and also the use of natural RHA would be an important contribution to sustainability and preservation of environment by civil construction. / O emprego de cinza de casca de arroz (CCA) natural no concreto visa contribuir para a sustentabilidade da construção civil, destinando de maneira adequada, esse material que antes seria considerado um resíduo poluente. Porém, é necessária a investigação das consequências em substituir parte do cimento por CCA natural para produzir concreto com finalidade estrutural. Neste sentido, o objetivo deste trabalho foi avaliar a durabilidade de concretos produzidos com teor de 15 % de substituição parcial do aglomerante por CCA natural, frente à expansão devido à reação álcali-sílica (RAS) e à penetração de íons cloretos, assim como, sugerir medidas preventivas através do uso de adições minerais. No presente estudo, a CCA natural foi utilizada em substituição parcial ao cimento Portland no estado em que se encontra ao sair dos fornos de queima (sem controle de temperatura), diretamente na betoneira para sofrer auto-moagem com os agregados. Foi investigada a neutralização das RAS da CCA natural pelo emprego de cimentos com adições minerais (CPIIZ, CPIII e CPIV), assim como foram realizadas as substituições adicionais de parte do cimento CPIIZ por cinza volante (10, 15, 20, 30 e 40 %). Na investigação da RAS foram empregados os métodos de expansão acelerado a 80 °C em barras de argamassa acompanhado pela microscopia eletrônica de varredura (MEV) e difração de raios-X (DRX), e os métodos de longa duração a 38 °C e acelerado a 60 °C em prismas de concreto. Na investigação da resistência a penetração de íons cloretos foi empregado o método de penetração de íons cloretos por imersão em solução salina (EPCI) dos concretos produzidos com CCA natural e cimento CPIIZ adicionados de cinza volante (0; 12,75 ou 17 %) e nas relações água/aglomerante(a/ag) de 0,45; 0,55 e 0,65. A análise dos resultados do EPCI foi realizada com base no coeficiente angular da equação da reta (K ) obtido a partir das profundidades médias de penetração dos períodos investigados. Neste trabalho verificou-se que, no ensaio em barras de argamassa a CCA natural gerou expansão acima do permitido por norma nas misturas com cimento padrão, enquanto o cimento CPIIZ com adição a partir de 20 % de cinza volante se mostrou mitigador da RAS. Através desses resultados pode-se verificar que o efeito mitigador da RAS aumentou proporcionalmente com a adição de cinza volante. Além disso, o cimento CPIV mostrou excelência em mitigar a reação expansiva. A análise de MEV identificou os produtos característicos da RAS nas amostras contendo CCA natural e a DRX verificou que as amostras retiradas das misturas com maior teor de adição mineral apresentaram picos de hidróxido de cálcio (CH) com menor intensidade e ainda, que as misturas com CCA natural apresentaram maior quantidade de carbonato de cálcio. Em relação aos prismas de concreto moldados a 60 °C, os resultados mostraram maior expansão na mistura de CPIIZ com CCA natural, mas ela se manteve abaixo do limite máximo de expansão preconizado pelo ensaio. As misturas de CPII-Z com CCA natural adicionadas de 10 e 15 % de cinza volante mostraram melhor eficiência em mitigar a expansão. Em relação aos prismas de concreto moldados a 38 °C os resultados ainda não são conclusivos aos 12 meses, porém as misturas que apresentaram maior expansão em 12 meses foram as de CPII-Z com CCA natural e 15 % de cinza volante, de CPII-Z com CCA natural e CPII-Z com CCA natural e 10 % de cinza volante, respectivamente, entretanto, todas abaixo do limite máximo de expansão aos 24 meses, preconizado pela norma brasileira. Através das análises dos resultados do EPCI concluiu-se que as adições minerais proporcionaram melhorias ao concreto com maiores idades devido ao efeito pozolânico. Além disso, os melhores resultados obtidos foram nos traços com menor relação a/ag, provavelmente devido ao maior consumo de cimento que aumenta a quantidade de CH para interagir com a CCA e a cinza volante. Portanto, as misturas de cimento Portland com CCA natural e cinza volante atendem aos parâmetros de durabilidade do concreto, e com isso o uso da CCA natural seria um importante contribuinte na sustentabilidade e preservação do meio ambiente pela construção civil.

This study evaluates question of alkali–silica reaction (ASR) in hybrid system, which was designed in the bachelor's thesis, to meet the requirements of EN 197-1 and classified to the Blastfurnace CEM III/C cements. The durability of this system is a great unknown. For this reason, the same methods (ASTM C1260, ASTM C289 and ASTM C856) were used to observer the ASR effects as the ones used to observer the Portland cement based concrete. Supplementary methods include determination of compressive strengths according to EN 196-2 and scanning electron microscopy to observe the microstructure. Hybrid system results were compared to two different types of cements, CEM I and CEM III/B. From the results of the ASR evaluation assays, it was found that the hybrid system (CEM III/C-HB) and CEM III/B showed the lowest tendency to ASR. The results of the supplementary methods showed that CEM III/C-HB compressive strength increases after 14 days within NaOH by 43 % in comparison to 28 days strength. Based on those results, it is sure that the CEM III/C-HB shows little susceptibility to ASR.

Nowadays, the waste sands from the water glass production have no utilization and due to high alkali content are considered as a dangerous waste. So the aim of this thesis is to find and study some possibilities of their utilization in the building industry. First of all, some necessary analysis of these sands were performed and then some advantages and disadvantages of their application for production of materials based on portland cement and alkali activated materials were studied. Characteristics of fresh and hardened pastes, mortars and concretes containing these waste sands were determined. The most tested properties were their workability and their compressive and flexural strength. Close attention for the risks of alkali-silica reaction and for options of its suppressing by the mineral admixtures was paid.

The work is divided into two parts. The first part deals with the description of unbound and bound base layers and their comparison. Furthermore is presented the description of the recycled concrete, its properties, production, improvement and issues. International experiences with recycled concrete technology are described as well. The practical part is focused on laboratory testing of concrete recycled material taken from the highway D1. The aim of this part is to determine whether the concrete can be recycled back into unbound or bound base layers and concrete casing.