Asphalt Mix Design and performance

Premature flexible pavement distress became a major concern in Indiana. As a result, a study was conducted investigating the major underlying factors. Pavement sections were investigated based on a factorial study with four factors comprised of climate, truck traffic, pavement base type, and wheel path. The distresses evaluated were rutting, thermal cracking and stripping. All were evaluated against control sections with zero distress. The pavement condition of each section was determined. Laboratory tests of field sample included physical properties, dynamic creep and recompaction. Results of the study indicate that the Asphalt Institute mix design criteria identify an asphalt content that is too high. In place densities were found to be inadequate and a recommendation was made to use higher field compactive effort. The USAE Gyratory Testing Machine (GTM) was used in laboratory studies to recompact density and air voids. Testing confirm that the in situ asphalt content was too high. Gap graded gradations were found to be prone to rutting. Benefit is shown in using dynamic modulus to evaluate mixtures. A statistical analysis method, discriminate analysis, was used to accurately predict mixture field performance using laboratory data