Effects of crumbed para rubber on permanent deformation resistance of hot mix asphalt

Abstract

In Thailand, natural para rubber (Hevea Brasiliensis) is gaining application in asphalt pavement construction. The natural rubber element helps extending the life period of asphalt pavement. Currently para rubber in a latex form is slowly added to hot asphalt binder and mixed together using shear mixer. An alternative of adding para rubber into asphalt pavement is applying para rubber crumbs into the hot mix asphalt (HMA) during the batch mixing process which is called “Dry Process”. The dry process has an advantage on its simplicity of quality inspection and less modification in the hot mix plant production process. This study has investigated the effects of adding crumbed para rubber particles on the engineering properties related to permanent deformation resistance of asphalt concrete. In this study, the asphalt mixture is prepared via Marshall Mix design, which contained with limestone and asphalt cement of Pen 60/70 at 5.4% by total weight. Crumbed para rubber at 2% by total volume was added in asphalt mixture via two methods, dispersive mixing method and layer method. The specimens that prepared from each method were compacted to cylinder shape according to the requirement of testing standard using Gyratory compactor. The specimens were tested to find resilient modulus and dynamic creep responses. The results showed that adding crumbed para rubber in aggregate by dispersive mixing method is the most effective method. It has increased significantly the resistance to permanent deformation compared with the conventional mixture.