Effect of styrene-butadiene copolymer coating on properties of rubberized cement-based composites

Abstract

Properties of improved strain capacity and high shrinkage cracking resistance make rubberized cement-based composites suitable for large surface applications such as pavements and thin bonded cement-based overlays. Microstructurally, the interfacial transition zone (ITZ) between rubber aggregate and cementitious matrix is different from that encountered with conventional aggregates. It is universally accepted a reduction in mechanical properties due to the low stiffness of rubber aggregates. However, transport properties are possible to be improved and comparative with conventional concrete or mortar if bonds between rubber particle and cementitious matrix were induced by pre-coating rubber aggregates to become hydrophilic and preventing air-entrapment phenomenon’s during mixing and placing composites. In this study, two distinct solutions were suggested to improve properties of composites such as using air-detraining admixture and styrene-butadiene copolymer as agent for rubber aggregate coating. Rubber particles with sizes 0–4 mm were incorporated in mortar as 30% sand replacement by volume. Microstructural analysis by Scanning Electron Microscopy (SEM) clarified the dense interface due to bonds generated by coagulation of the cement paste-polymer on the rubber surface. The initial experimental results showed a reduction in air permeability of composites modified with styrene-butadiene copolymer. As expected, this treatment method also contributed positively to mechanical properties of composites, especially direct tensile strength.