Investigation On Performance Of Scrap Tire Rubber Modified Asphalt Paving Materials

Grinded crumb rubber from waste tires is used to modify asphalt materials in this study. The performance of crumb rubber modified asphalt binders and mixtures produced from local materials are tested and investigated. The purpose is not only to reduce the environmental pollution but also to improve the performance of the paving materials.Based on the review of the existing specifications home and abroad, rubber gradation is decided, which obtained by mixing two types of crumb rubber in a certain proportion. Physical properties, such as specific gravity, moisture content and metal content, are tested, and essential measures are taken to make rubber properties satisfy the requirement.In order to investigate the properties of rubber asphalt binder, five types of asphalt rubber are prepared from two types of basic asphalt binder and four different rubber contents. Effects of preparation condition and rubber content on viscosity of the binders are investigated by means of rational viscosity test. Dynamic shear rheometer (DSR) tests are performed on the original binder samples, samples after short term ageing and samples after long term ageing respectively to analysis the viscoelastic properties of crumb rubber modified asphalt. It is found that when the rubber content is between 15% and 21% by weight of the modified binder, the high temperature performance and fatigue resistant property of the binder become better as the rubber content increases. This range is also proved to be acceptable for practical application.Four types of asphalt mixtures are selected for the performance investigation, including two gap graded asphalt rubber mixtures whose binders were produced from different basic asphalt, an open graded asphalt rubber mixture (AR-OGFC) and a stone mastic asphalt (SMA) with traditional binder. The stiffness test, wheel tracking test, indirect tensile test are adopted for assessing high temperature susceptibility, water sensitivity and long term ageing property of the mixtures. The results indicate that asphalt rubber mixtures have lower temperature susceptibility and greater resistance to moisture damage compared to SMA, while SMA shows a better durability after long term ageing condition.