Evaluating the robustness of self‐consolidating concrete: an approach to the mix design procedure

This paper aimed to develop a method to analyze and rank self‐consolidating concrete (SCC) according to its robustness, considering isolated and simultaneous variations in its main components, like water (±6%) and cement content (ΔC±), in three matrices with binder to aggregate ratio (rich, intermediate and poor). In the experimental campaign, only water variations (±6%) were considered, and the cement content variations were considered in the analytical method. The method regarded the behavior of SCC in fresh and hardened states and turned out to be potentially useful to the academic community and the industry. The simple additive weighting method was used for that reason, which is probably the most adopted among methods for decisions with multiple variables due to its simplicity. Among the families studied, the poor mixture presented the lowest robustness with variation in water content due to the higher initial w/c ratio. However, for the condition ΔC±, the poor mixture achieved the second‐best robustness index. The rich mixture behaved differently as it was ranked second for ±6% of water and the worst for ΔC± due to slump‐flow and segregation results. The intermediate matrix presented the highest robustness in both conditions analyzed, water (±6%), and cement content (ΔC±)

Experimental method for investigation of impact of the addition of polymer fibers on drying shrinkage and cracking for concretes

This study presents an investigation of a fiber-reinforced concrete (FRC) with use of fibers of polypropylene, polyvinyl alcohol, and recycled polyester in the amount of 0.50%, seeking to analyze the impact of the fiber additions on mechanical properties, drying shrinkage, and cracking. Regarding flexural strength, a reduction of up to 25% of the value was observed for FRC. The residual strength of FRCs was increased values 20 times higher than the reference concrete. The addition of fibers also increased the void content of the matrices and, therefore, drying shrinkage of the reference matrix up to 74%. The fiber additions increased the internal tensile stresses of the FRC of up to 12.0 MPa. Besides the increase in resistance, the FRC presented formation cracks with openings 8 times smaller than the concrete

Comparison of the fire resistance behaviour of structural insulated panels with expanded polystyrene core treated with intumescent coating

It is necessary to study fire safety in buildings because the lack of knowledge in the behavior of materials has taken too many lives. However, this field has designed innovating construction systems and materials such as structural insulated panels (SIP), this is a much more practical alternative for fastest constructions, reducing the amount of material waste, offering cleaner and lighter works, its thermal insulation properties in possible fires and better durability in construction in the account of the various internal compositions. The objective of this article is to evaluate and analyze the fire resistance of two SIP for dividing and structural walls, made up of a core of expanded polystyrene (EPS) with dimensions of 3150x3000mm, one covered with cement board and the other one covered with gypsum plasterboard, both are treated with intumescent paint. The samples were exposed to the fire curve based on the ISO 834: 2014 standard and then analyzed and compared with each other. The obtained results indicate the incorporation of gypsum plasterboards provides a gain of 45 min of resistance to fire, compared to the system it only contains cement board, positively influencing gypsum in the stability and property of the thermal insulation of the panels. Likewise, it was found that intumescent coatings application effectively helps to give the SIP greater protection against fire

Impacto nas propriedades mecânicas do concreto curado sob baixas temperaturas

O processo de cura das matrizes cimentícias é muito importante na determinação das suas propriedades noestado endurecido. Nessas circunstâncias, o concreto pode sofrer sérias avarias quando exposto às severasvariações térmicas. As baixas temperaturas de cura em que as matrizes cimentícias são expostas podeminfluenciar nas propriedades no estado endurecido, principalmente nas idades iniciais, prejudicando osprocessos de desfôrma e escoramento. Locais de frio intenso devem seguir procedimentos específicos dedosagem e aplicação de uma matriz cimentícia. Sendo assim, essa pesquisa objetivou analisar a influência datemperatura de cura no comportamento mecânico e físico de concretos em diversas temperaturas de cura,tanto nas idades inicias como nas mais avançadas. Observou-se que a diminuição na temperatura de curaproporcionou aumento de resistência em até 26% na idade de 28 dias nos concretos analisados, apesar de queapresentaram desenvolvimento lento das propriedades mecânicas nos 7 dias iniciais. Concretos com maiorconsumo de cimento apresentaram melhor desempenho nas idades inicias quando submetidos às temperaturasmenores que 3 oC. Porém, percebeu-se que a cura em baixas temperaturas é capaz de proporcionar misturasmais íntegras em idades avançadas, visto que atingiram maior velocidade de propagação onda ultrassônica eresistência, pelo fato de ocorrer a hidratação residual do cimento.Palavras-chave: Concreto, cura em baixa temperatura, propriedades mecânicas

Analysis of highway trafficability under the pathological manifestations in the concrete plates: A case study

O descomedido incremento da frota nacional de veículos fomenta debates quanto à infraestrutura rodoviária, principalmente na construção, ampliação ou recuperação das estradas existentes. Nesse contexto, observa-se que a Rodovia Mário Quintana (ERS-118) apresenta alarmante estado de conservação e trafegabilidade, proveniente, principalmente, do grau de deterioração elevado das placas de concreto constituintes do pavimento. O objetivo deste trabalho foi determinar a integridade funcional dessa rodovia segundo avaliação e análise das manifestações patológicas das placas de concreto. Fundamentado no método desenvolvido pelo U.S. Corps of Engineers (USACE), através do índice de condição do pavimento (ICP), o trabalho foi estruturado em três partes: (a) método de avaliação das placas, (b) análise dos resultados e (c) conclusão. Os resultados obtidos indicam que a rodovia não apresenta mais funcionalidade e que sua vida útil, por conseguinte, findou-se.Palavras-chave: patologia, pavimentos de concreto, rodovia ERS-118, Método ICP, trafegabilidade.The increase of the Brazilian vehicle fleet highlights the discussion about road infrastructure, especially the construction, expansion or rehabilitation of the existing roads. In this context, it is noted that the Mario Quintana highway (ERS- 118) shows poor conditions of conservation and trafficability, coming mainly from the high degree of deterioration of the constituents of the concrete pavement slabs. The objective of this study was to determine the integrity of this highway, following an evaluation and analysis of pathological manifestations of concrete pavement. Based on the method developed by the U.S. Corps of Engineers (USACE) through the pavement condition index (PCI), the work was divided into three parts: (a) method of evaluation, (b) result analysis and (c) conclusion. The results indicate that the highway has no more functionality and service life, consequently, consummated.Keywords: pathology, concrete pavement, highway ERS-118, ICP method, trafficability