Efeitos da variabilidade de agregados de RCD sobre o desempenho mecânico do concreto de cimento Portland

Abstract

Construction and demolition waste (CDW) generation is a serious environmental issue. Waste recycling plants have emerged in Brazil. These companies receive waste from various sources, whose composition diversity influences the behavior of aggregates for mortars and concretes. The variability of composition leads to a decrease in the quality of the aggregate produced, restricting them to applications with a low performance requirement. In this work, aggregates produced by a recycling plant were characterized according to the current Brazilian standard, aiming at the application in concretes. Two collections of the recycled aggregates were made, with interval of six months, obtaining three particle size fractions for each collection, corresponding to sand, gravel 0 and gravel 1. For each sample collected, the gravimetric composition of the recycled aggregates was determined by visual analysis and coarse aggregates were classified as mixed residue aggregates (MRA).Concretes with recycled fine aggregate replacement showed satisfactory results of compressive strength, with an increase of 18% in relation to reference concrete, while concretes with recycled coarse aggregates obtained a reduction of 20.6%. Indirect tensile strength tests showed that the four mixtures with total MRA replacement showed a decrease between 5.2% and 19.5%, relative to the reference. The other concretes have obtained results similar or superior to the reference. The largest variation, among the concrete of the two collections, in this property was 13.2%. With the insertion of recycled coarse aggregates, there was a reduction of the modulus of elasticity of the concrete, in relation to the reference concrete. The reductions obtained in this property were in the range of 15.8% to 40.6%. The largest variation of this property, of 13.3%, between the concretes with aggregates obtained in the two collections, was for the concrete with substitution of 100% of fine aggregate. Better results were obtained for concrete with fine MRA.