Permeability and leaching properties of recycled concrete aggregate as an emerging material in civil engineering

Abstract

In this article, a study of the threshold gradient and leaching properties for recycled material, namely, recycled concrete aggregate (RCA), was conducted. The RCA in this study is a material that comes from recycling concrete debris. A series of tests in permeameter apparatus in a constant head manner were conducted. The test method has been improved to eliminate common mistakes, which occur when the constant head method is used. During the following study, aggregates with gradations equal to 0-8, 0-16, and 0.05-16 mm were tested. The tests were conducted on gradients ranging from 0.2 to 0.83. This range of tested gradients led to the evaluation of the flux velocity and indicated non-Darcian flow. For engineering applications, the threshold gradients for three RCA blends were calculated using a statistical analysis. The average coefficient of permeability, kavg, for linear flow was equal to 1.02 × 10-4-1.89 × 10-4 m/s. In this paper, suffosion analysis was also conducted for the three blends in order to eliminate the possibility of particle movement. Moreover, for RCA blend 0-16 mm, leaching properties was examined. It was found that the concentration of chlorides, sulphates, and heavy metals in the water solution does not exceed the permissible standards. This paper ends with conclusions and proposals concerning the threshold gradients obtained from the statistical analysis, suffosion analysis, and flux velocity.