Volume 41, Issue 2 (March 2013)
Use of Sweep Test for Emulsion and Hot Asphalt Chip Seals: Laboratory and Field Evaluation
Currently, the scope of the standard test method for sweep test of bituminous emulsion surface treatment samples (ASTM D7000) is limited to emulsion-based chip seals only. To this end, the objective of this study is to evaluate the sensitivity of the sweep test for both emulsions and hot asphalts, with respect to aggregate mineralogical types, aggregate precoating, aggregate moisture content, asphaltic materials type, and application rates of asphaltic materials. For the field evaluation, fifteen chip seal test sections were prepared with three asphaltic materials and five aggregates in a 9-acre parking lot. Two years after construction, each of the 15 sections were visually inspected for aggregate loss and bleeding. Each section was given a distress rating. The % aggregate loss from the sweep test was then compared with the field distress rating. Both laboratory and field tests indicate that overall, expanded shale lightweight aggregate is better than any crushed stone, whereas clay lightweight performed the worst among the six aggregates tested in this study. Precoated expanded shale lightweight aggregates performed better than uncoated shale lightweight aggregates, with respect to % aggregate loss. Between the two hot asphalts, PAC-15 performed better than AC20-5TR. In the case of hot asphalt, the % aggregate loss increases as moisture content increases in oven dry, air dry, and saturated surface dry aggregates. However, for emulsion, air dry aggregates performed the best. For both emulsion and hot asphalt, an increase in asphaltic materials application rate reduces the % aggregate loss significantly. Distress rankings in all 15 sections, except for one PAC-15 section, matched sweep test rankings. Overall, the results indicate that the sweep test using both emulsion and hot asphalt can be an effective tool for evaluation of performance of chip seals.