ASPHALT CONCRETE DAMAGE ASSOCIATED WITH EXTREME LOW-TEMPERATURES

Current distress analysis practices and material specifications associ ated with low temperatures, including recent developments by the Strat egic Highway Research Program, do not address the potential for locali zed damage associated with thermal incompatibility of asphalt concrete components. The analytical approach used to explain transverse surfac e cracking assumes a homogeneous pavement material. Although this appr oach produced satisfactory results for the prediction of low temperatu re cracking, it may obscure other forms of damage related to exposure to extreme low temperatures. This paper discusses localized forms of d amage related to the vast difference in the coefficients of thermal co ntraction of asphalt concrete components (binders and mineral aggregat es). Microscopic examination of asphalt concrete samples exposed to lo w temperatures revealed the presence of hairline cracks within the asp halt matrix. The examination also revealed deterioration of the bond a t the aggregate/binder interface. The observed damage patterns explain the results of mechanical testing conducted using indirect tensile st rength and three point bending procedure. Analysis demonstrates the po tential impact of the observed forms of damage on pavement performance , it also explains results published by other researchers.