Experimental Study On Bonding Properties Of Recycled Concrete

This research is a vital sub-item of: "analysis on mechanical properties and microstructure of recycled concrete" which is funded by Natural Science Foundation of Heilongjiang Province (item approval number: D0314)In this paper, based on domestic and overseas research work of mechanical properties of recycled aggregate concrete (RAC), by 75 pull-out test specimens, a systematic investigation was conducted to evaluate the bonding properties of RAC. The following research work was carried out:(1) By 4 groups of RAC pull-out test specimens with different Coarse Recycled Concrete Aggregate(CRCA) replacement ratio of 0% 33%,66% and 100%, the relationship between the bonding strength of RAC and CRCA replacement ratio was obtained.(2) By 4 groups of RAC pull-out test specimens with same CRCA replacement ratio of 100%, but different Fine Recycled Concrete Aggregate (FRCA) replacement ratio of 0%,33%,66% and 100%, the relationship between the bonding strength of RAC and FRCA replacement ratio was obtained.(3) RAC "maximum use"(MU) mix proportion was suggested after crush test. Based on the MU mix proportion, by adjusting the water/cement ratio (w/c), the relationship between compress strength and w/c, bonding strength and compress strength of RAC was obtained.(4) Based on the MU mix proportion, 4 groups of RAC pull-out test specimens with different concrete cover thickness was designed to evaluate concrete cover thickness's influence on bonding strength of RAC, and maximum effective concrete cover thickness was suggested; 4 groups of RAC pull-out test specimens with different anchorage development length was designed to evaluate the relationship between bonding strength and anchorage development length.(5) By adding fly ash, adding slag, or adding both fly ash and slag these three different methods, mineral admixture's influence on RAC was studied. And the results provide experimental foundation for appropriate use of mineral admixture in RAC.This study may serve as experimental foundation to further research and practical application of recycled concrete.