Microscopic analysis of the interaction between crumb rubber and bitumen in asphalt mixtures using the dry process

A microscopy study of the modification of bitumen with crumb rubber was carried out to investigate its application in asphalt mixtures using the dry process. The modification involved the transfer of maltenes to the rubber and carbon black to the bitumen, causing the absorption of the lighter-oil fractions of bitumen. The modification increased the stiffness of the bitumen, resulting in an improvement in the binder’s resistance to rutting. The changes in shape and porosity developed around the crumb rubber particles by the rubber–bitumen interaction allow the most favourable particle size (<200 μm) to be established for the dry-process in crumb rubber-modified asphalt mixtures.