Evaluation of Effects of Asphalt Binder on Properties of Hot-Mix Asphalt at Intermediate Temperatures

Asphalt binder is an essential component of asphaltic mixtures. The performance of asphaltic mixture is directly related to mechanical characteristics of the binder. With the development of new material characterization methods for both asphalt binder and asphaltic mixture, there is a need to re-evaluate the relationship between the properties of binder and asphaltic mixture such that a proper understanding and selection of asphalt binder can be made to improve the performance of asphaltic mixture. In this study, the effects of asphalt binder properties on asphaltic mixture at intermediate temperature were evaluated using new materials characterization methods. Five asphalt binders and five asphalt mixtures containing these binders with same aggregates sources were tested. Four of the binders were modified with different techniques. Complex shear modulus and monotonic constant shear-rates tests were conducted on asphalt binders whereas dynamic modulus and indirect tensile strength tests were conducted on the corresponding mixtures. The effects of modification techniques on the properties of asphalt binders and relationship between properties of binder and asphaltic mixture were evaluated in this study. The results indicated that the modulus of asphalt binder directly affects that of asphalt mixture, as expected. The failure strain of asphalt binder controls that of asphalt mixture. However, the shear strength and fracture resistance, critical strain energy density in this case, of asphalt binder are not directly correlated with those of asphaltic mixtures. It is believed that the interaction between asphalt binder and aggregates, instead of asphalt binder alone, plays a significant role in the fracture of asphaltic mixture.