Comparison of concrete properties made from recycled brick, virgin brick, and natural stone as coarse aggregates

Abstract

This study presents the comparative mechanical and durability properties of concrete made from different types of aggregate that includes natural stone, crushed virgin clay brick, and recycled brick concrete. Concrete with 2500 psi, 3000 psi, and 3500 psi target strength was prepared using mix design method suggested in ACI code. Cylinder, cube and prism specimens were prepared from these concrete. Using these samples, physical, mechanical and durability properties of these different types of concrete were measured. Results suggest that using brick and recycled brick concrete as coarse aggregate achieved compressive strength is 6-11% less than the target strength. Whereas, for natural stone, achieved strength was 2-5% higher than target strength as per ACI mix design method. Modulus of elasticity was determined as per ASTM C 469.Results suggest that modulus of elasticity of natural stone aggregate is 20% higher than that of crushed clay brick aggregate concrete of equivalent strength and 29.5% higher than recycled brick concrete as aggregate. Poisson’s ratio is also determined for natural stone aggregate, which varied between 0.209-0.176, for crushed clay brick aggregate Poisson's ratio was between 0.209-0.176 and for recycled brick concrete as aggregate it was between 0.230-0.164. Shrinkage data were recorded up to 150 days after casting; results show that for equivalent strength and environmental parameters for concrete with virgin brick as coarse aggregate, drying shrinkage was found to be higher than natural stone and recycled brick aggregate. Cube samples (6’’) were then tested for water permeability using the AT 315 machine as per EN 12390-8 “Depth of penetration of water under pressure”. Experimental results and subsequent analysis indicated that water permeability of crushed brick aggregate is 53% to 74% higher than that of concrete made from natural stone aggregate, in the same way permeability of recycled brick concrete as aggregate is 102% to 140% higher than that of natural stone aggregate concrete. Cube samples (4”) were then tested for density, absorption, and voids in hardened concrete according to ASTM C642. Results show that bulk density in crushed clay brick aggregate concrete is almost 13% lower than natural stone aggregate concrete and recycled brick concrete as aggregate is almost 16% lower than natural stone aggregate concrete. Absorption in virgin crushed clay brick aggregate concrete is 50% to 52% higher than that of concrete made from natural stone aggregate, again absorption in recycled brick concrete as aggregate is 96% to 116% higher than that of natural stone aggregate concrete. Therefore, concrete with brick and recycled brick concrete as aggregate should be used with caution due to degradation of its mechanical and durability parameters.