Effects of recycled ceramic aggregates on internal curing of high performance concrete

High performance concrete (HPC) is widely used in concrete structures because of its excellent mechanical properties, good workability, and outstanding durability. However, as HPC usually has a low water to cement ratio, the hydration of cement would cause rapid decrease in the humidity inside concrete, leading to autogenous shrinkage of HPC. Internal curing is a method to maintain the internal humidity of concrete by introducing water storage materials into HPC. In this study, three different waste ceramic aggregates are employed as internal curing materials for HPC. The physical properties and the chemical compositions of the three ceramic materials are studied through microscopic tests. The internal curing efficiency is then investigated through mechanical tests and autogenous shrinkage tests of HPC. The experimental results show that the properties of HPC are greatly affected by the porosity and replacement ratio of the ceramic aggregate. A better shrinkage control can be achieved by using the aggregate with larger porosity, while higher strength is obtained when the replacement ratio is lower. In general, all three recycled ceramic aggregates are highly efficient in reducing autogenous shrinkage of HPC while maintaining a satisfactory level of mechanical properties, and wall tile with 20% replacement ratio is considered to perform the best.