Influence of the Type of Binder and Crumb Rubber on the Creep and Recovery of Crumb Rubber Modified Bitumen

This investigation reports the influence of the type of binder and crumb rubber gradation and dosage rate on the creep and recovery properties of crumb rubber modified bitumen (CRMB). Two types of binders, air blown and blended, were used with two gradations of crumb rubber, fine and coarse, at three dosage rates, 8, 10, and 12%. The morphology of these 12 binders were characterized by using environmental scanning electron microscopy (ESEM). Furthermore, energy dispersive X-ray spectroscopy was carried out on the samples to identify the chemical composition of the network structure as seen from ESEM. All the samples were subjected to creep and recovery tests by using a dynamic shear rheometer at five different temperatures of 46, 52, 58, 64, and 70 degrees C. A generalized Voigt-Kelvin model was used to model the creep and recovery response of the material for all the temperatures tested. It was found that the nature of the binder plays a critical role on the development of morphology of CRMB. This morphology influences the creep and recovery characteristics of the final blend. The fibril diameter and the number of network junctions as determined through the image processing of ESEM images and the Voigt-Kelvin model parameters were found to be related. DOI: 10.1061/(ASCE)MT.1943-5533.0000608. (C) 2013 American Society of Civil Engineers.