The effects of recycled brick and water/cement ratios on the physical and mechanical performance of recycled aggregates concrete

In this paper, the effects of recycled Refractory Brick Aggregates (RBA) and water/cement ratio (w/c) on the physical and mechanical properties of concrete were experimentally studied. For this purpose, three series of mixes, with different compositions were prepared. In the first series, conventional reference concrete was made with 100% of Natural Aggregates (NA). In the second series, concrete was manufactured by replacing 20% of coarse NA with coarse RBA. In the third series, concrete was produced by replacing 20% of coarse and fine NA with coarse and fine RBA. In all mixes, three w/c ratios (w/c = 0.59, 0.47 and 0.38) were evaluated. The following parameters were examined in this experiment: water absorption, water porosity, density, Ultrasonic Pulse Velocity (UPV), compressive strength and dynamic modulus of elasticity. The experimental results showed that the performance of concrete made with RBA is slightly inferior to that of conventional concrete. On the other hand, the deterioration of UPV and dynamic modulus of elasticity of concrete made with 20% coarse and fine RBA were slightly higher than that of concrete made with 20% of coarse RBA. The same results are observed for the water absorption and water porosity. However, replacing 20% of coarse and fine RBA leads to an improvement in the concrete's compressive strength and density. Meanwhile, based on a comparison with existing data, it is found that lower w/c ratio resulted in lower porosity of concrete, and the decrease of porosity generally led to the improvement of the performance of concrete.