The present work aims to contribute to the study and development of methodologies for shrinkage tests of self-compacting concrete (SCC) using the addition of polypropylene (PP) microfibers as a variable to validate the correlations between the shrinkage tests. The objective of this work was to evaluate, through correlations between the area and the age at which the cracks appeared, the role of PP fibers as a control for this pathology. Reference SCC traces with additions of 6 mm and 12 mm microfibers were created for this purpose. For the shrinkage tests, the criteria of the ASTM C1579:2013 (plates) and ASTM C1581:2016 (rings) standards were used. The microfibers showed a significant reduction in cracks in the SCC, its reduction rate ranging from 40% to 70%, also presenting a delay in its appearance, which varied from 9 to 20 days for the appearance of the first crack.

Recycled crumb rubber can be sustainable used in mortar both to mitigate nature aggregate consumption, reducing environmental pollution, as well, to improve the acoustic and thermal performance of buildings, without damaging its mechanical properties. This paper explores workability, microstructure, mechanical, thermal and acoustic properties considering increasing contents of crumb rubber (0%, 5%, 10%, 15% and 20% replacement, by volume, of fine aggregate). Mortar characterization tests were carried out in the fresh and hardened state. It has been found that replacing the aggregate with scrap tyre rubber reduced the compressive strength on average 12% and 67% and for tensile strength 35% and 53%, for the contents of 10% and 20% respectively, compared to the reference. Furthermore, it was found that the reductions in thermal conductivity reached 16% and 29% and an increase in acoustic attenuation on average 12% and 13%. Moreover, scanning electron microscopy images were analyzed, justifying the mechanical results obtained. Although the experimental results indicated that the workability and mechanical strengths decreased with the increase of rubber replacement rate, the studied mixtures met the standard specifications, and thus suitable for walls and ceilings coating applications, improve the acoustic and thermal performance of buildings and as a sustainable material.

Concrete structures are susceptible to several factors during their life cycles, which can cause various problems. This situation can be avoided in many cases if Structural Health Monitoring (SHM) is used. However, such monitoring is often expensive due to the large number of sensors and the use of data acquisition systems (DAQ). In this context, self-sensing cement composites (SSCCs), monitoring themselves without sensors by incorporating conductive fillers in their composition, provide a better piezoresistive effect. In this research, the Arduino platform and analog to digital converters (ADC) modules were tested, and a prototype of a low-cost DAQ was developed for monitoring SSCCs. The devices were analyzed from the compression tests on the mortar specimens, and the results were compared to measurements obtained from the reference equipment (professional DAQ). The results showed a good sensitivity and an adequate correlation between both devices in some cases. It showed that the Arduino platform has the potential to be used in the experimental monitoring of SSCCs, however it needs to be combined with an ADC module.

The excessive production of new tires and the inappropriate disposal of waste tires have caused serious environmental and public health problems. To properly dispose of this environmental liability, these rubber residues have been used in cement composites to improve some of their properties in the hardened state. This study evaluates the incorporation of rubber and vermiculite residues in concrete in terms of mechanical and acoustic properties. Different concrete compositions were defined where rubber waste and vermiculite were used to replace the natural sand mass. To characterize the concretes, mechanical and acoustic tests, and analysis of the microstructure of the material were carried out to better understand its properties. An improvement in the acoustic properties can be seen in the composites with rubber and vermiculite. Thus, the great contribution of this research is the development of concrete compositions for acoustic barriers, technically viable, adding environmental benefits. problems liability state mass concretes tests Thus barriers viable benefits

The use of steel fibers in concrete affects its rheological properties in the fresh state and increases its energy absorption capacity in the hardened state. Rubber fibers come from tires and when incorporated into concrete, they promote an improvement in its damping factor. This work aimed to evaluate the use of rubber fibers on the mechanical properties of concrete reinforced with steel fibers. The evaluated properties were: compressive strength, tensile strength, static and dynamic modulus of elasticity and damping. The mixes of the tested concretes varied the consumption of steel and rubber fibers. From the results found, it can be seen that the rubber associated with steel fibers within the concrete mixtures improves the damping rates of the material. factor were strength found material

Structural health monitoring (SHM) techniques aim to detect and prevent failures in constructions, although their use may require many sensors, which makes this technique expensive and laborious. In this sense, the use of self-sensing cementitious composites based on the piezoresistivity effect could be a solution to some monitoring problems. Thus, the evaluation of the piezoresistive effect is commonly performed by analyzing the linearity between mechanical forces and the variation of electrical resistivity, through the coefficient of determination (R2). However, this work has been used to perform the analysis through Pearson's correlation in samples of self-sensing cementitious composites with graphite addition. The results obtained have shown that Pearson's correlation has the potential to be used for the evaluation of the correlation between electrical resistivity and mechanical forces to verify the piezoresistive effect in the cases studied.

RESUMO Neste trabalho foi analisada a microestrutura do concreto pigmentado com e sem resíduos de borracha, por meio do microscópio eletrônico de varredura, visando sua aplicação na fabricação de pisos intertravados. Verificou-se que o concreto de referência (sem borracha) apresentou pasta densa e compacta e de acordo com o aumento do teor de borracha no concreto, observou-se a tendência da crescente porosidade e número de vazios na pasta de cimento, aparecimento de microfissuras e zona de transição acentuada entre os agregados e a pasta, com exceção para o traço contendo 5% de borracha. Estas análises possibilitaram um melhor entendimento do comportamento mecânico desses concretos. O aglomerante empregado foi o cimento Portland branco estrutural. Objetivando atribuir ao piso intertravado mais uma vantagem arquitetônica e estética empregou-se um pigmento do tipo inorgânico a base de óxidos de ferro e cromo de tonalidade azul. O resíduo de borracha utilizado em substituição parcial ao agregado miúdo (areia natural) foi proveniente do processo de recauchutagem de pneus, e adicionado ao concreto nas seguintes proporções 2,5%, 5,0%, 10%, 20%, 30% enquanto o teor de pigmento foi mantido constante, sendo 6% em relação à massa de cimento. Com relação aos ensaios mecânicos, os resultados indicaram que, para os traços contendo 2,5% e 5,0% de resíduos de borracha a norma ABNT NBR 9781:2013 é atendida com relação à resistência característica à compressão aos 28 dias (maior ou igual a 35 MPa), fato que não aconteceu para os traços com 10%, 20%, 30%. Considerando as composições do concreto estudadas nesta pesquisa, pode-se afirmar que o emprego de resíduos de borracha como substituto parcial da areia é uma alternativa de reciclagem do produto que agregada muito ao meio ambiente e evita o descarte inadequado deste passivo ambiental.

ABSTRACT In this work the microstructure of pigmented concrete with and without rubber residue was analyzed by scanning electron microscope, aiming its application in the manufacture of interlocking block. It was verified that the reference concrete (without rubber) presented dense and compact paste and according to the increase of the rubber content in the concrete, the tendency was observed to increase the porosity and number of voids in the cement paste, appearance of cracks and zone of sharp transition between aggregates and paste, except for the trace containing 5% rubber. These analyzes allowed a better understanding of the mechanical behavior of these concretes. The binder employed was structural white Portland cement. In order to give the interlocking block another architectural and aesthetic advantage, an inorganic type pigment based on iron oxides and blue chrome was used. The rubber residue used as a partial replacement for fine aggregate (natural sand) came from the tire retreading process and was added to the concrete in the following proportions 2.5%, 5.0%, 10%, 20%, 30% while the pigment content was kept constant, being 6% in relation to the cement mass. Regarding the mechanical tests, the results indicated that, for the traces containing 2.5% and 5.0% of rubber residues, the ABNT NBR 9781:2013 standard is attended with respect to the characteristic compressive strength at 28 days (greater than or equal to 35 MPa), which did not happen for the traces with 10%, 20%, 30%. Considering the concrete compositions studied in this research, it can be stated that the use of rubber waste as a partial substitute for sand is an alternative for recycling the product which adds a lot to the environment and avoids the inappropriate disposal of this environmental liability.

Resumo A escória de forno elétrico foi usada como substituto do agregado graúdo natural na produção de peças de pavimentação de concreto. O traço de concreto 1:2:3:0,51 (cimento:areia:agregado graúdo:água) foi definido para alcançar uma resistência à compressão de 35 MPa. Quatro grupos de concreto foram preparados: um traço referência e três outros com a escória substituindo o agregado comum nas proporções de 25%, 50% e 75% (em massa). A resistência à compressão não foi influenciada pelo teor de escória, no entanto, foi influenciada pelo tempo de cura, uma vez que a amostra com 75% de escória apresentou 13,5% de aumento na resistência aos 56 dias em relação aos 7 dias de cura. A absorção de água apresentou uma pequena redução com a adição da escória. Os resultados da resistência à compressão e absorção de água atenderam aos requisitos das normas técnicas brasileira, indicando que os blocos podem ser utilizados para pavimentação de tráfego leve. De maneira geral, os resultados deste estudo destacam a influência do processo produtivo na qualidade final da escória, e a necessidade do estabelecimento de legislação e normas técnicas específicas, para nortear e promover o uso seguro da escória de forno elétrico em concreto.

Abstract In this study the electric arc furnace slag was used as coarse natural aggregate substitute in concrete paving blocks production. The concrete mixture was defined by using weight proportions in the ratio of 1:2:3:0.51 (cement:sand:coarse aggregate:water) in order to obtain a compressive strength of 35 MPa. Four groups of concrete were prepared: a reference recipe and three others with the slag replacing the natural aggregate in the proportions of 25%, 50% and 75%. The compressive strength was not influenced by the slag content; however, it was influenced by the curing age, as the sample with 75% of slag addition had its compressive strength increased by 13.5% from 7 to 56 days. Water absorption presented a slightly reduction with slag addition. The results of compressive strength and water absorption met the Brazilian technical requirements, making the paving blocks suitable for use in light vehicle traffic. The results obtained in this study highlight the influence of the production process in the final quality of the steel slag, and the need of stablishing technical and environmental requirements to guide and promote the safe use of electric arc furnace slag in concrete.

RESUMO O pneu inservível é um material de difícil degradação, seu acúmulo ou descarte inadequado causam graves impactos ao meio ambiente. Pneus empilhados ficam sujeitos à ocorrência de incêndios, devido a capacidade térmica que possuem, além de serem ambientes propícios para proliferação de vetores transmissores de doenças. A utilização de resíduos de borracha de pneus na produção de peças de concreto para pavimentação tem sido uma alternativa viável para destinação ambientalmente adequada destes resíduos e para redução do consumo de recursos naturais, contribuindo para sustentabilidade da construção civil. Este trabalho avalia o comportamento do concreto com adição de resíduo de borracha de pneus na produção de peças de concreto para pavimentação, onde o agregado miúdo é substituído em massa pelo resíduo de borracha nas proporções de 2.5, 5.0, 7.5, 10, 20 e 50%. Na produção dos concretos foram empregados os seguintes materiais: cimento Portland, agregados miúdos e graúdos, resíduos de borracha e aditivo superplastificante. Foram realizados ensaios de resistência à compressão em pisos intertravados aos 07 e aos 28 dias. A análise gráfica foi realizada a partir dos valores de resistência e teor de borracha, e os resultados mostraram que para um determinado intervalo de porcentagem de substituição do agregado miúdo por resíduo de borracha, houve uma melhora na resistência à compressão dos pisos intertravados, e para até 10% de substituição da areia natural pelo resíduo de borracha de pneus, é possível empregar este concreto na produção de pisos de concreto para tráfego pesado, segundo as recomendações da norma brasileira.

ABSTRACT The waste tire is a material of difficult degradation, its inadequate accumulation or disposal cause serious environmental impacts. Stacked tires are subject to fires due to thermal capacity which have, besides being prone environments for proliferation of vectors transmitting diseases. The use of tire rubber waste in the production of paving blocks has been a viable alternative to environmentally proper disposal of this waste and to reduce the consumption of natural resources, contributing to sustainable construction. This work evaluates the behavior of the concrete with addition of tire rubber waste in the production of paving blocks. The fine aggregate was substituted by rubber waste in proportions of 2.5, 5.0, 7.5, 10, 20 and 50%. Portland cement, fine aggregate, coarse aggregate, rubber waste and superplastic additive were used in the concrete. Compression strength tests were performed in interlocking floor parts at 7 and 28 days. The graphical analysis was using values of resistance and rubber content, and the results showed that for a given range of proportion of substitution of fine aggregate by rubber waste, there was an improvement in the compression strength of concrete paving blocks, and with substitution of up to 10% of sand by rubber waste is possible to use this concrete to produce interlocking floor for heavy traffic, according to the recommendations of the Brazilian standard.

RESUMO Neste estudo realizou-se uma investigação para a confecção de concretos com alta resistência, baixa densidade e excelente desempenho térmico, com a finalidade de executar construções energeticamente eficientes. Concretos leves estruturais foram estudados utilizando duas granulometrias de argila expandida (C05 e C15), onde houve a substituição do agregado graúdo pela em 0, 25, 50, 75 e 100%. Para promover a manutenção da consistência e resistência, utilizaram-se superplastificante e sílica ativa nas misturas. Com base na metodologia utilizada, os concretos foram caracterizados física e mecanicamente, de acordo com as normas nacionais e internacionais vigentes. A densidade dos concretos, no estado endurecido, variou de 1.787 a 2.400 kg/m³ e, quanto a resistência à compressão, variou-se de 26 a 53 MPa, aos 7 dias de idade. O ensaio de condutividade térmica, por meio do método da placa quente protegida, foi realizado de acordo com a EN 12667, onde observou-se uma variação de 0,61 a 1,00 W/mK. Informações microestruturais da zona de transição interfacial entre agregado e matriz de cimento foram obtidas com a finalidade de analisar a relação com a resistência mecânica. A investigação revelou que, com a adição de argila expandida (C05 e C15) e sílica ativa nos concretos, houve a redução da densidade e da resistência mecânica, entretanto as características térmicas melhoram.

ABSTRACT In this study an investigation was carried out for the execution of concretes with high strength, low density and excellent thermal properties, in order to execute energy-efficient constructions. Structural Lightweight Concretes were studied using two different granulometries of expanded clay (C05 and C15), where the coarse aggregate was replaced by 0, 25, 50, 75 and 100%. To promote the maintenance of consistency and resistance, superplasticizer and silica fume were used in the mixtures. Based on the methodology used, the concretes were physically and mechanically characterized, in accordance with current national and international standards. The density of the concretes, in the hardened state, ranged from 1,787 to 2,400 kg/m³ and, for compressive strength, ranged from 26 to 53 MPa at 7 days of age. The thermal conductivity test, using the protected hot plate method, was performed according to EN 12667, where was observed a variation of 0.61 to 1.00 W/mK. Microstructural information of the interfacial transition zone between aggregate and cement matrix were obtained with the purpose of analyzing the relationship with mechanical resistance. The investigation revealed that, with the addition of expanded clay (C05 and C15) and silica fume in the concretes, there was reduction of the density and the mechanical resistance, while the thermal characteristics improved.

RESUMO A busca por materiais sustentáveis na construção civil, que apresentem menor massa específica, melhores desempenhos térmicos e manutenção das resistências mecânicas, representa grande desafio na produção e avaliação de concretos leves estruturais (CLE), o qual desponta como um material alternativo ao concreto convencional. Neste estudo realizou-se uma investigação para a confecção de concretos com alta resistência, baixa densidade e excelente desempenho térmico, com a finalidade de executar construções energeticamente eficientes. CLE foram estudados utilizando duas granulometrias de argila expandida (C05 e C15), onde houve a substituição do agregado graúdo pela C15 em 0, 25, 50, 75 e 100%. Para promover a manutenção da consistência e resistência, utilizaram-se superplastificante (SPA) e sílica ativa (SA) nas misturas. Com base na metodologia utilizada, os concretos foram caracterizados física e mecanicamente, de acordo com as normas nacionais e internacionais vigentes. A densidade dos concretos, no estado endurecido, variou de 1.787 a 2.400 kg/m³ e, quanto a resistência à compressão, variou-se de 26 a 53 MPa, aos 7 dias de idade. O ensaio de condutividade térmica, por meio do método da placa quente protegida, foi realizado de acordo com a EN 12667, onde observou-se uma variação de 0,61 a 1,00 W/mK. Informações microestruturais da zona de transição interfacial (ZTI) entre agregado e matriz de cimento foram obtidas com a finalidade de analisar a relação com a resistência mecânica. A investigação revelou que, com a adição de argila expandida (C05 e C15) e SA nos concretos, houve a redução da densidade e da resistência mecânica, entretanto as características térmicas foram melhoras.

ABSTRACT The search for sustainable materials in civil construction, which presents a lower specific mass, better thermal performance and maintenance of mechanical resistance, represents a great challenge in the production and evaluation of structural lightweight concrete (SLC), which emerges as an alternative material to conventional concrete. In this study an investigation was carried out for the construction of concretes with high strength, low density and excellent thermal properties, in order to execute energy-efficient constructions. SLC were studied using two different granulometries of expanded clay (C05 and C15), where the coarse aggregate was replaced by C15 at 0, 25, 50, 75 and 100%. To promote the maintenance of consistency and resistance, superplasticizer (SPA) and silica fume (SF) were used in the mixtures. Based on the methodology used, the concretes were physically and mechanically characterized, in accordance with current national and international standards. The density of the concretes, in the hardened state, ranged from 1,787 to 2,400 kg/m³ and, for compressive strength, ranged from 26 to 53 MPa at 7 days of age. The thermal conductivity test, using the protected hot plate method, was performed according to EN 12667, where was observed a variation of 0.61 to 1.00 W/mK. Microstructural information of the interfacial transition zone (ITZ) between aggregate and cement matrix were obtained with the purpose of analyzing the relationship with mechanical resistance. The investigation revealed that, with the addition of expanded clay (C05 and C15) and SF in the concretes, there was reduction of the density and the mechanical resistance, while the thermal characteristics were improved.