Mechanical properties and durability of rubberized and SBR latex modified rubberized concrete

Abstract

This paper analyses how rubber waste, used as replacement of fine aggregate in concrete mixes, affects mechanical properties and durability of concrete: freeze-thaw resistance, water absorption by immersion, and sulphate resistance. Concrete was modified by carboxylated styrene butadiene rubber (SBR) latex to get better bonding properties between rubber and hardened cement paste. Control specimens were made of concrete mix without crumb rubber. Scrap tyre rubber powder (crumb rubber – CR) of fraction 0/1mm and 1/2mm was used as fine aggregate. CR was used to replace a portion of fine aggregate at 5% of the total aggregate content. CR of fraction 0/1mm was found to improve freeze-thaw resistance: freeze-thaw resistance test results were similar to those of concrete with traditional air entrainment systems. On the contrary, coarser rubber particles of fraction 1/2mm had a negative effect on freeze-thaw resistance of concrete. These findings can be explained by the smoother texture and a more regular shape of coarse rubber particles up to 2 mm in size and the rougher texture and irregular shape of fine particles up to 1 mm in size. A complex profile of rubber particle surface results in higher volume of air voids, higher closed porosity and higher freeze-thaw resistance of concrete modified with crumb rubber. The test results confirmed that concrete modified with crumb rubber of smaller fraction had higher closed porosity and higher freeze-thaw durability factor Kf. The results also confirmed that Kf values calculated from concrete porosity parameters can be conveniently used to predict freeze-thaw resistance and durability of concrete. The tests have shown that the modification of concrete with rubber waste has no positive effect on sulphate resistance, compressive strength and modulus of elasticity.