Concrete containing recycled aggregates: Estimated lifetime using chloride migration test

Abstract

Abstract This paper presents a study regarding the durability of concrete containing Recycled Coarse Aggregate (RCA) from the largest civil construction waste plant in Latin America, CTR Grajau, located in Sao Paulo, Brazil. Conventional reference concretes were produced with natural aggregates and water/cement ratios of 0.35, 0.45, and 0.55. The recycled concretes were produced by replacing the Natural Coarse Aggregate (NCA) of the reference concretes with RCA in percentages of 50% and 100% by volume. Specimens were submitted to tests to determine the apparent porosity, capillary absorption coefficient and\xa0compressive\xa0strength. To verify durability aspects, the diffusion coefficients of chlorides (obtained by a procedure adapted from ASTM C 1202:2017) and electrical\xa0resistivity (obtained using a Wenner probe)\xa0were determined. Results demonstrated that NCA substitution with RCA increased porosity, with a consequent increase in the capillary absorption coefficient and a reduction in compressive strength. Total replacement of NCA with RCA reduces the concrete service life, calculated using Fick’s Second Law of Diffusion, by at least 40% for concretes with water/cement (w/c) ratio equal to 0.35, while a partial replacement (50%) reduces the service life by approximately 22%, considering a marine environment and 40\u202fmm of cover thickness. The use of w/c minimum ratios, detailed RCA characterization and pre-wetting are some of the methods proposed for the application of the material for structural purposes. The lifetimes of the different concretes were determined.