Polymer/fiber modified asphalt fracture mechanisms and microstructure relationships to distresses and environmental factors

Asphalt concrete pavements have been showing signs of early distress in areas of thermal cracking, aging, fatigue cracking, rutting, and ravelling/stripping which are diminishing pavement performance. Therefore, the focus of the research in this thesis is a determination of the role of polymer modifiers on the properties of asphalt cement and performance of asphalt concrete. The key to establishing this linkage is a fundamental understanding of the microstructure, morphology, adhesion, locus of fracture, and fracture toughness of polymer modified asphalt (PMA).; Tests were developed for microscopic, image, and fracture analyses enabling microstructural and morphological investigation and examination of crack propagation, fracture mechanisms, and locus of fracture. The general failure mechanisms seen in asphalt specimens through fracture analysis were yielding, crazing causing the formation of microvoids and fibrils, and ultimate failure. Tests have also been proposed for adhesion and fracture toughness evaluation of PMA and polymer modified asphalt cement (PMAC).