Characteristics of crumb rubber modified (CRM) asphalt concrete

Abstract

The mix design for CRM asphalt concrete with the Marshall method and laboratory tests to evaluate low temperature behaviors and temperature susceptibilities of CRM asphalt concrete are presented. The mix design was performed using one asphalt cement (120/150 penetration grade), five aggregate gradations for three rubber contents (0, 3, and 5% by weight of aggregate) and both pretreated and untreated crumb rubber (passenger tire). All mixtures satisfied the Marshall mix design criteria. For laboratory tests, two asphalt cements (85/100 and 120/150 penetration grade), three aggregate gradations for three rubber contents (0, 3, and 5% by weight of aggregate) and two types of pretreated crumb rubber (passenger and industrial tires) were used. The addition of crumb rubber did not significantly affect the overall temperature susceptibility of the mixtures. It did, however, substantially decrease the mixture modulus at any given temperature. The decrease in modulus was accentuated as the content of crumb rubber increased. The potential for thermal cracking decreased with the amount of crumb rubber. This demonstrated that a CRM asphalt mixture could relieve stress build up by its ability to strain.