Computed Tomography Scanning for Quantifying Chipseal Material Volumetrics

Abstract

In the reported study the viability of using computed tomography (CT) scanning for assessing flushing defects in thin sprayed seal (chipseal) surfacings was explored. The study was undertaken to investigate the micromechanical interactions that occur within chipseal layer materials in order to examine their relationship to the origination of flushing, using CT scanning techniques. In particular, the effectiveness of using image analysis techniques to analyze the changes in air voids that occur within a chipseal layer during loading was investigated. The presented study was based on laboratory testing of chipseal pavement samples (cores) from in-service pavements in the Auckland and Waikato regions of New Zealand. The cores, with diameters of 200 mm and thicknesses ranging from 32.4 mm to 44.5 mm, were subjected to varying levels of lateral cyclic loading using a wheel-tracking machine, and the deformation that occurred on the surface of the cores was measured. Two small specimens were extracted from each loaded core, one specimen from the wheel-tracked area of the core and the other from the untracked area of the core. The specimens were scanned using a CT scanner, and the resulting scan images were analyzed using image analysis techniques to determine the distribution of air voids within each specimen. The air voids within the tracked and untracked specimens of each core were compared to examine the changes that had occurred to the distribution of air voids during loading. The results of the study showed that image analysis is an effective tool to analyze air voids within a chipseal layer.