Evaluation of Various Modification Methods for Enhancing the Performance of Recycled Concrete Aggregate

Due to the existence of the attached mortar, the performance of the recycled concrete aggregate (RCA) is inferior to the natural aggregate, which significantly limits its wide application in industry. In this study, five kinds of modified solutions were used to modify the surface of RCA, and the modification effects were compared. The results showed that sodium silicate, nano-silica (NS), Bacillus pasteurii and soybean powder had relatively good modification effects on RCA, which could reduce the crushing value and water absorption, and increase apparent density. The composite solution (15% sodium silicate and 2% NS) and soybean powder solution had better modification effect. The 28 d compressive strength and splitting tensile strength of recycled aggregate concrete (RAC) prepared by RCA modified by soybean powder solution were 4.6% and 5.2% higher than those prepared by RCA modified by composite solution, respectively. This indicates that among the five kinds of modified solutions, soybean powder solution has the best modification effect on RCA, and the optimal soaking time of soybean powder solution is 8 h. At this time, the crushing value, water absorption and apparent density of RCA are 12.8%, 5.3%, and 2653 kg/m³, respectively. The research results of this study provide a reference for the modification of RCA and its efficient utilization.