TOP-DOWN CRACK PROPAGATION IN BITUMINOUS PAVEMENTS AND IMPLICATIONS FOR PAVEMENT MANAGEMENT

Abstract

Surface-initiated longitudinal wheel path cracking has been cited as a widespread mode of failure among asphalt concrete pavements and yet, few theories have been presented that fully explain the mechanism. This study serves as complementary follow-up to the research presented on initiation of top-down cracks, as it explores and explains the mechanisms for propagation of top-down cracks and attempts to forecast the implications for pavement design. It may be concluded that designing and analyzing pavements using the current approach that employs averaged pavement conditions and equivalent single axle loads will neither predict nor address longitudinal wheel path cracks that initiate and grow down from the surface. Research was performed that showed that existing design and evaluation methods that use averaged conditions are inadequate for predicting this type of surface cracking. It was proven that the propagation of surface-initiated longitudinal cracks advances only under critical conditions and that crack development is highly dependent on differential pavement temperature gradients. This factor is addressed in the conventional approach to pavement analysis; therefore, an alternative approach to designing and rehabilitating pavement should be formulated, or the existing approach adjusted, to include surface-initiated longitudinal wheel path cracks. A concept formulated to identify crack length stages in terms of time, in order to better describe crack growth, may be the initial step in addressing top-down cracking using pavement management.