Reuse of recycled concrete aggregates (RCA) in new concrete structures is limited due to their high water
absorption and weak bonding to new matrix. These unfavorable properties are associated with the thin
layer of old mortar attached to the surface of original aggregates. In this paper, a novel approach of RCA
surface treatment by means of microbial carbonate precipitation (MCP) was studied. Factors influencing
MCP on RCA were investigated. It was found that the amount of MCP peaks at pH = 9.5 and increases with
higher temperature, bacteria concentration, or calcium concentration. Enhanced MCP on RCA can be
achieved through proper control of culturing and precipitating conditions. Results show that surface
modification of RCA through MCP is feasible evidenced by increasing weight and reducing water absorption
of treated RCA