Effects of Asphalt Binder Grade on the Performance of Rhode Island Hot-Mix Asphalt

The primary objective of the present study was to formulate guidelines to select an appropriate asphalt binder grade to produce high performance Hot Mix Asphalt (HMA) in Rhode Island (RI). Three different Performance Grade (PG) asphalt binders were used: PG64-28, 70-28 and 76-28. A series of volumetric mix designs utilizing the Superpave mix design process were performed. An automatic Asphalt Pavement Analyzer (APA) was acquired, to predict the performance of HMA specimens fabricated with RI asphalt binders and mineral aggregates. HMAs used in the study were dense graded asphalt mixes and wearing course mixes, i.e., dense graded friction mixes and a Paver Placed Elastomeric Surface Treatment (PPEST). Dense graded mixes studied were the RI Class I-1 surface course and Superpave mixes using Bailey gradations. APA test results indicated that asphalt binders with higher temperature grades would reduce rutting, but it should be observed to have good cracking resistance in the field. Interestingly, HMA specimens with PG76-28 binder did not produce less rutting than the PG70-28 specimens. Also, it has been observed that HMA with crushed fine aggregate had less rutting than the mixes with natural sand. It is believed that low temperature cracking occurs when the stress due to temperature change is higher than the tensile strength of the mixes. It was found that mixes with PG64-28 binder exhibited the lowest tensile strength. However, HMA specimens with PG76-28 did not provide higher strength than mixes with PG70-28. In addition, there were no significant differences in tensile strength between specimens prepared with crushed fine aggregates and natural sands. It was also observed that the specimens prepared at Optimum Binder Content (OBC) provided highest tensile strengths compared to the ones with other binder contents. The outcome of the study will provide the RI Department of Transportation and contractors with guidelines to select proper asphalt binders for HMAs. Thus, the pavement will have fewer premature distresses and will last longer. Consequently, it will reduce maintenance and rehabilitation costs, and will allow repaving of more miles.