Physical and Mechanical Properties of Treated Recycled Aggregate Concretes: Combination of Mechanical Treatment and Silica Fume

Abstract

This paper presents the combined effect of the mechanical treatment of recycled aggregate (RA) and the use of silica fume (SF) in the concrete mixes. In the first step, the RA is treated by the optimized ball mill method (oBMM) to decrease mortar content. In the second step, the SF is used to enhance the negative effects of the attached old mortar (AOM) that has remained in the RA. In this method, natural aggregate (NA), RA, and treated RA (tRA) at various ratios (20%-40%-60%) with 0%-5%-10% SF are used in the mixes. After 28 days, tests are carried out on the specimens. The results show that the mechanical treatment followed by the SF combination significantly enhances the performance of recycled aggregate concretes (RACs). Satisfactory test results are generally obtained for treated recycled aggregate concrete (tRAC) produced with up to 60% tRA and 10% SF. This improvement can be explained as the consequence of the removal of AOM by oBMM and eliminating the adverse effects of the remaining part of AOM in tRA by SF addition in concrete.