Improving the mechanical properties of recycled concrete aggregate using chopped basalt fibers and acid treatment

This paper presents the results of a study that investigated the improvement of the mechanical properties of recycled concrete aggregate (RCA) produced by adding chopped basalt fibers (BF) with contents of 0.1%, 0.3%, 0.5%, 1%, and 1.5% by total volume of the mix to treated and untreated recycled aggregates. The recycled aggregates were surface treated by pre-soaking them in a 0.1 M hydrochloric acid (HCl) solution for 24 h to remove the adhered mortars to improve the bond between the recycled aggregate and the cement. In addition, chopped BF was added to normal concrete (NA) mixes as a control for comparison. The results showed that using chopped BF minimally enhanced the compressive strength of the concrete mix but significantly improved its flexural and splitting tensile strength. Furthermore, the optimum BF content that produced the same splitting tensile and compressive strength as NA was 0.5% for untreated RCA and 0.3% for treated RCA, while the flexural strength was 0.3% for untreated RCA and 0.1% for treated RCA.