Experimental Study on Interfacial Strength of the High Performance Recycled Aggregate Concrete

There are an Interfacial Transition Zone(ITZ) between the recycled aggregate and the new mortar matrix body. The ITZ is still the weakest position in the recycled aggregate concrete. In this paper, the microhardness of the ITZ and the interface between the old cement paste of recycled aggregate and new motar matrix body of recycled aggregate concrete in different strength grade are tested by using digital microhardness meter. The testing results indicate the microhardness value of the recycled aggregate is much higher than that of the ITZ of the recycled aggregate concrete and the microhardness of the interface between the old cement paste of recycled aggregate and the new mortar matrix body is the lowest. The testing result also shows the value of microhardness increase gradually with the testing distance growth from the interface to the new mortar matrix body and it keeps constant when the testing distance from the interface to the new mortar matrix reaches 100um. The microhardness of the old cement paste and new mortar matrix in the ITZ grows with the strength grade growth of the recycled aggregate concrete.It is concluded from the experiment that the mineral admixtures can improve the performance of ITZ and enhance the microhardness of recycled aggregate concrete.The microhardness can reflect the interfacial strength of recycled aggregate concrete well and the testing results would provide important references for explosion the failure mechanism of recycled aggregates concrete.