The Effects of Recycled Aggregates on Compressive Strength of Concrete

Demolished concrete can be used as recycled concrete aggregate (RCA) for construction purposes. In the research, the compressive strength of concrete made from 100% recycled coarse aggregates and 100% natural coarse aggregates was compared. The values of compressive strength of the natural aggregates concrete (NAC) served as a control. 24 concrete cubes (150 x 150 x 150mm) each for the NAC and RCA were casted making a total of 48 concrete cubes. Three cubes for each category was cured for 3 days, 7 days, 21 days and 28 days respectively. Concrete mix ratios of 1:2:4 and 1:1.5:3 were used in both cases. The results show clearly shown that the compressive strength of RAC was higher than those of NAC at the early ages before day 12. It can be deduced from the graph that the compressive strength of RAC was higher than that of NAC at early ages while the compressive strength of NAC was higher than that of RAC at later ages. This means that RAC will have better usage in quick set concrete where early strength is desired.