Understanding asphalt binder cracking characterization at intermediate temperatures: Review and evaluation of two approaches

Abstract

Accurate characterization and proper selection of asphalt binder can prolong the fatigue life of asphalt pavements. The objective of this study was to evaluate the linear amplitude sweep (LAS) test and the binder fracture energy density (BFE) test using a broad range of asphalt binders with a particular emphasis on the identification of appropriate failure definition. Three unmodified binders and three modified binders were investigated. LAS test results revealed that the failure criteria in the existing specification (35% reduction in G*sinδ and peak shear stress) did not capture the improved performance expected from modified binders whereas the peak stored pseudo strain energy (PSE) failure criterion did. This could be attributed to the larger strain levels that binder samples undergo before the instant of failure defined by the peak stored PSE. Fracture energy density measured with the BFE test on fractured specimens clearly distinguished between unmodified and modified binders. It was concluded that binder response can influence the outcome of performance comparison parameters. For comparable binder types, binders with a more ductile behavior may exhibit a more strain tolerant response in the LAS test whereas stiffer binders appeared to show a more fracture tolerant response in the BFE test.