Estudo experimental e numérico de agregado graúdo reciclado tratado para aplicação em concreto

Abstract

The large production of construction waste (CW) has led several countries to define management policies and invest in recycling this material, in the construction industry. Part of the CW consists of concrete waste, and coarse recycled concrete aggregates (CRCA) are considered to be of the best quality for concrete manufacturing. Research shows that the porosity of CRCA is higher than the porosity of natural coarse aggregates (NCA), and this may be responsible for the loss of quality of concretes with CRCA. The treatments proposed to reduce the porosity of CRCA have been applied to the final product of CRCA, with little proven efficiency in the properties of concretes. Another important aspect nowadays is the introduction of numerical methods, which can assist in the evaluation of test results and computational elaboration procedures for concrete compositions. In this context, this study proposes a method of treating AGRC, and numerical analysis that contributed to improving the quality of AGRC properties, and the introduction of numerical analysis of the tests for implementation in computer programs. The CRCA was obtained from the processing of concrete specimens and characterized. The AGRC treatment method, to reduce its porosity, was carried out by wear in a ball mill, “Los Angeles” abrasion testing equipment. A proposal for a numerical analysis of the treatment method was defined, and the characterization of CRCA and CRCA treated (CRCA T) was carried out. For the absorption kinetics of AGRC and AGRCT, a numerical model was proposed based on the curves of the absorption tests. Still on the absorption aspect of these aggregates, a study was carried out on the influence of the absorption of the different phases of formation of these aggregates. For the application and analysis of the behaviors of the CRCA and CRCAT, conventional (CC) and special (SCC) concretes were produced. In obtaining the compositions of the SCC ‘s, dosage methods used in previous studies were used. Numerical methods were used to determine the dosage of the superplasticizer by the saturation point; and for the composition of aggregates. The concrete behaviors were evaluated taking into account the use or not of 80% of the water of absorption of the CRCA and CRCA T, being considered the effective waters of the concrete. The properties in the fresh and hardened states were evaluated according to the types of CRCA used, as well as statistical analyzes of the porosities of the CRCA and CRCA T, and of the compressive strengths of the concretes. The numerical models correlated with the analyzed phenomena and the results obtained from the CRCAT characteristics indicated that it is possible to improve the physical properties of the CRCA with the proposed method, which was observed by the reduction of the CRCAT porosity in relation to the CRCA. The analysis of the results showed that, in general, concretes with CRCA T performed better than concretes with CRCA and with only natural aggregates (NCA). In a global analysis, SCC without absorption water showed better properties in the hardened state compared to SCC with the use of 80% of absorption water. The ratio between the cost of energy spent on concrete in relation to its resistance, indicated the most efficient treatment.