Evaluation of Asphalt Damage and Cracking Development with Seismic Pavement Analyzer
Fatigue cracking in asphalt pavements is an indicator of structural failure, and early detection of fatigue cracking would allow for improved preventive maintenance. The evaluation of cracking relies on the distress's being visible and possibly in advanced stages. Detection of load-related cracking at an early stage or before initiation is greatly needed. The portable seismic property analyzer (PSPA), a nondestructive device that monitors the change in modulus in pavement surface layers, was used in this study to measure the change in pavement stiffness response at the same time as the development of load-associated cracking. PSPA tests were conducted at the FHWA Turner-Fairbank Highway Research Center accelerated loading facility on full-scale test pavements being subjected to repeated wheel loading to induce cracking. PSPA measurements taken at a predetermined number of loading passes were evaluated to find crack initiation or propagation. The patterns for the amount of modulus reduction before and after the initiation of cracking were measurable and different for modified and unmodified binders. An unmodified asphalt section lost only between 25% and 33% of the original modulus before the initiation of surface cracks, whereas a polymer-modified asphalt lost between 62% and 57%. The cracking was top-down given the aged condition of the test sections.