Evaluation of pre-coated recycled aggregate for concrete and mortar

► The physical performance of modified recycled aggregate was satisfied with specification requirement. ► Too much or less coating paste both reduced aggregate crushing strength and optimum coating thickness was 0.035mm. ► Sulfoaluminate cement paste with fly ash can improve the mechanical property and durability of recycled concrete or mortar. The reuse of recycled aggregate can ease the aggregate shortage problem and reduce environment pollution. Improvement of recycled aggregate surface structure is one of key techniques to enhance performance of recycled concrete. In this research, the surface structure of recycled aggregate was modified in several kinds of paste besides involved impregnation process was performed under a controlled laboratory environment. The test results show that physical performance of pre-coated recycled aggregate was within the range of specification requirement and surface-coated recycled aggregate with paste thickness of 0.035mm resulted in a higher physical performance. In addition, compressive strength of concrete increased as the water to cement ratio of coating paste increased. After 56days of curing, compressive strength increased by up to 10% compared with the corresponding control concrete. The sulfate attack resistance test results show that strength loss of mortar significantly reduced after recycled fine aggregate modified.