Comportamento mecânico e durabilidade de concretos de ressitência normal e de alta resistência contendo agregados de resíduos de concreto e metacaulim

Abstract

In the present study, the mechanical behavior and durability of classes C30 and C60 concretes were evaluated, using 100% recycled coarse concrete aggregate and 15% of metakaolin as Supplementary Cementitious Material (SCM), dosed following the principles of the Compressible Packing Model (CPM). The stress versus strain behavior and the tensile strength of the mixtures were determined after 28 and 90 days of curing and the durability was evaluated from capillary water absorption tests and accelerated penetration of chloride ions at 90 days of cure. In addition, physical tests of total water absorption, void index and specific mass at the same age were carried out. The use of metakaolin as SCM led to mixtures with a lower total amount of cementitious materials (up to 40% reduction). All mixtures showed a slump of 180 ± 30 mm and design strengths were reached for 28 days of age. Due to the tendency to achieve greater compressive strength performance at early ages, no expressive increases (2-6%) of resistance were observed in the mixtures with metakaolin for up to 90 days. For the mixtures containing only Portland cement, they achieved a performance of (8-17%) over time. By using 100% recycled aggregate, a greater amount of total mortar volume was obtained, but it did not degrade the durability of concrete with the presence of metakaolin. For both classes, the use of metakaolin showed a tendency of improvement in the concrete durability.