Determination of crack growth rate parameters of asphalt mixtures using the Superpave IDT

Abstract

A mixture's resistance to crack propagation will ha\'e a dirett effect on the cracking performance of asphah pavements. Therefore, it would ~ useful to have a practical and reliable system to determill( crack growth rate parameters (fracture parameters) of asphalt mixtures. Given the advent and continuing implementation of the Superpave volumetric mixture design procedure. it would be particularly useful if the system were compatible with specimens produced \\i th the Superpa\'e Gyratory compactor. Fracture parameters could be used to optimize mixlUTe designs and would also provide the fundamental properties needed to accurately predict pa\'l~ment performance. A complete testing, data acquisition, reduction. and analysis system was developed in this study to delermifl( fracture parameters using the Superpave !DT (indirect tension test). The theoretical relationships and data reduction procedures de\'eloped preclude the need to measure crack growth rate directly during testing, or the need to obtain or estimate asphah mixture stiffness or any other property to analyze the fracture test data. These two features not only make fracture testing easier to perform, but it may also be argued thai better consistency can ~ achieVed, since the variability introduced b)' using properties determined from independent tests, as well as the inherent inaccuracies invoh'ed in measuring crack gro~1h rate directly, are eliminated. It also eliminates the need to produce and test another set of specimens. Based on tests performed on two Superpave mixtures, the system developed was shown to provide rational and consistent fracture test results that compared favorably with fracture parameters published in the literature for similar mixtures. Therefore, the system appears to pro\'ide a viable approach for determining fracture resistance of asphalt mix~s produced with the Superpave Gyratory compactor or of field cores obtained from pavements in the field.