INCORPORATING PERFORMANCE REQUIREMENTS IN ASPHALT MIXTURE DESIGN

Abstract

In recent years transportation agencies have been focusing on performance-based asphalt mixture design to ensure durable pavements. Including performance in the design, phase allows the prediction of expected distresses, such as fatigue cracking, permanent deformation, and moisture damage. The main objective of this study was to identify a new approach to include performance testing in asphalt mixture design for the state of Maryland. The following specific objectives were identified to achieve this: (i) identifying the cracking and rutting criteria for asphalt mixtures in Maryland; (ii) assessing the repeatability of the selected performance tests; (iii) establishing model-based performance predictive approach for designed asphalt mixtures; (iv) adopting a non-destructive testing method (i.e., Ultrasonic Pulse Velocity – UPV) in Quality Assurance (QA) of asphalt mixtures. Two well-accepted and suitable performance tests for Maryland conditions were selected to address the first objective. These tests included the IDEAL Cracking Test (IDEAL-CT) for fatigue cracking and the High-Temperature Indirect Tensile Strength Test (HT-IDT) for permanent deformation. Such performance index tests were combined with volumetric requirements and benchmark analysis. Since mixture properties affect each of these typical distresses in asphalt mixtures and pavements differently, a Balanced Mix Design approach was adopted, BMD. The sources of variability in testing were quantified through round-robin testing between laboratories for the second objective. Based on the results and findings, an adjustment procedure was developed. For the third specific objective, a methodology was proposed for predicting field performance from laboratory testing and mixture volumetrics considering (i) well-accepted prediction models by the research community and (ii) fundamental asphalt material behavior parameters representing mix quality and well-related to performance. A sensitivity analysis of UPV regarding mixture volumetrics and testing conditions was carried out for the final objective. The resulting asphalt mixture stiffness from such an evaluation was then compared to the results from traditional destructive testing for pertinent conclusions. Based on these analyses and results, a framework was proposed for adopting UPV in the BMD mix design approach developed in this study. The research and methodology developed in this study can be used elsewhere, where similar materials are used.