Effect of Recycled Coarse Aggregate on the Compressive Strength and Modulus of Rupture of Concrete

The paper investigated the compressive strength and rupture modulus of recycled aggregate concrete when recycled aggregates from the regulated industry such as laboratories is used as partial substitute for natural coarse aggregates. The work determined and compared the compressive strength of recycled aggregate concrete with that of natural aggregate concrete. It applied the laboratory investigated technique. A standard mix ratio of 1:2:4:0.5 representing; cement, fine aggregate, coarse aggregate and water/cement ratio was used to produce the test cubes and beams, with subsequent 0%, 30%, 50%, 80% and 100% substitution of natural coarse aggregates with recycled coarse aggregates. The results showed that as the percentage content of recycled coarse aggregate in the mix increased, the compressive strength decreased. The natural coarse aggregate concrete gave a compressive strength of 43.6 N/mm2 and the recycled coarse aggregate concrete, 29.5 N/mm2, a decrease of 40%. At early stages of substitution, there was no significant change in the modulus of rupture but at higher percentages of substitution, it became significant. The natural coarse aggregate concrete gave a modulus of rupture of 5.67 N/mm2 while the recycled coarse aggregate gave 3.84 N/mm2.
Recycled concrete has been shown to be a viable option to decrease the demand on high quality natural resources and to limit the amount of waste that is disposed in landfills.