Effect of surface treatment by mineral admixture-magnesium potassium phosphate cement on the mechanical properties, durability, and microstructure of recycled aggregate concrete

Abstract

Magnesium potassium phosphate cement (MKPC), a clinker-free cement, was used as the recycled coarse aggregate (RCA) surface strengthening material to enhance the mechanical properties and durability of recycled aggregate concrete (RAC) under two surface treatment methods. The effect of strengthening slurry properties on RAC reinforcement was investigated by adding different types and amounts of mineral admixtures (MA). An interface model was prepared to detect the microscopic characteristics of interfaces. The results indicated that all MA-MKPC slurries improved the RAC macroscopic performances, attributed to the fact that MA-MKPC slurries effectively improved the RCA surface pore structure and promoted a secure connection with RCA or new mortar. MA-MKPC slurry properties significantly affected the performances of modified RAC, and the MA optimal dosage of 10 % was found. Furthermore, the pre-coating without pre-curing method outperformed the pre-coating plus pre-curing method, forming an enhanced new interfacial transition zone within the RAC.