Influence of coating recycled aggregate surface with pozzolanic powder on properties of recycled aggregate concrete

A two-stage crushing process was utilized to produce recycled aggregate (RA). The slump of concrete mixes prepared by technique of stone enveloped with pozzolanic powder (SEPP) was compared with those using normal mixing approach (NMA) or stone enveloped with portland cement (SEPC) approach. After 7 and 28 days curing, the compressive and flexural strengths were tested. The slump and strength results indicate that the new mixing technique contributes significantly to better workability and higher compressive and flexural strengths. The interfacial transition zone of recycled aggregate concrete was observed by a scanning electro microscope (SEM). The SEM results verify that the new mixing technique benefits to a denser interfacial transition zone.