This paper was presented at the `Pavement cost and performance evaluation strategies' session. Pavement design, construction and maintenance technology requires performance and behaviour prediction when subjected to various traffic loads and environmental conditions. SHRP developed the performance-based specification for asphalt cement (binder) and design methodology for asphalt concrete mixes. Superpave software is an innovative tool for mix design, pavement's performance prediction using deterioration models for rutting fatigue and low-temperature cracking. The Superpave low-temperature cracking model customizes the data acquired from the indirect tensile creep test at 1000 sec. loading time to predict the frequency and depth of cracks. It is based on the three dimensional finite element analysis which is a function of the diametral shape, Poisson's ratio and thickness to diameter ratio. This is considered to have several limitations for the users. Consequently, a research study was conducted to assess an alternative method, direct tension creep testing, and to use the results in the Superpave software for estimating fracture temperature and cracking frequency. In addition, the research compared the testing and analysis results with an alternative, more simple approach for estimating cracking frequency. This paper describes the experimental program to measure the visco-elastic properties of the asphalt mixes and the procedure used to analyse the results, including the application of the Superpave software. The basic findings were that fracture temperature estimates are highly dependent on the accurate determinations of the coefficient of thermal contraction of the mix, and that Superpave, in its present for has some major limitations in this regard. Furthermore, Superpave also has significant limitations in its flexibility to accommodate the inputs from low-temperature creep testing alternative method; namely direct tension. Finally, it was found that the simple model for predicting the frequency of) low-temperature cracking seemed to be just as reliable as the much more complex Superpave model, over the range of conditions used in the research study. (A
Abstract