Effects of packing on compressive behaviour of recycled aggregate concrete

It is well known that the packing of particles in concrete has great effects on the performance of concrete, but codified methods for measuring packing density are all carried out under dry condition, which tends to result in loose packing due to agglomeration of the fine particles. Nevertheless, a wet packing method has been developed recently to enable more accurate measurement of packing density. In this study, this wet packing method was extended to measure the packing density of the concrete mix of recycled aggregate concrete (RAC). Furthermore, three groups of concrete mixes with various aggregate proportions and W/C ratios were produced for compression tests. It was found that at given W/C ratio and age, the compressive strength, elastic modulus, toughness and specific toughness of RAC would increase with increasing packing density, indicating that the packing density is a key factor affecting the compressive behaviour of RAC. Hence, packing density optimization is a promising way of improving the performance of RAC.