Use of Surfactant to Improve Properties of Crumb Rubbers in Concrete Products

Abstract

Use of crumb rubbers from waste tires in concrete applications can help reduce environmental impacts from the massive waste tires. However, several studies show that incorporating crumb rubbers into concrete can decrease the mechanical properties due to their low strength and stiffness, and poor interfacial bond with cement paste. Since crumb rubbers are considered a hydrophobic material, they tend to repel water and segregate from fresh cement paste. This causes poor bond strength between cement paste and crumb rubbers and provides negative effects on concrete strength. This study aims to improve the performance of concrete mixed with crumb rubber or rubberized concrete by increasing the crumb rubber surface wettability (i.e., reduce its water repellant ability). A surfactant (Tergitol NP-10) is applied to the crumb rubbers in order to reduce solid/liquid interfacial tension between the crumb rubber and water. This modification should allow better attachment and bond between crumb rubbers and cement paste and hence, improve the concrete mechanical properties. The specimens are prepared using non-modified and modified crumb rubbers at the rate of 3% to 10% by volume. Three experiments are a carried out: Adhesive bond, compressive and flexural strength. Results show that the rubberized concrete mixed with modified crumb rubbers exhibit better bond and higher compressive and flexural strengths than those mixed with conventional crumb rubber.