Using a New Zealand Performance Specification to Evaluate U.S. Chip Seal Performance

Abstract

This paper reports the results of a chip seal research project in Texas where the researchers are using both quantitative and qualitative means to evaluate chip seal performance on rural roads. The team is making specific use of the Transit New Zealand (TNZ) T/3 “sand circle” test to measure the change in average texture depth over time and applying those measurements to the TNZ P/17 performance specification for allowable surface texture deterioration over the first year of chip seal performance. The results demonstrate the value of quantitatively characterizing the preseal surface condition as a benchmark against which to compare new chip seal performance. Those roads that had poor preseal surface conditions as exhibited by low macrotexture as measured by the T/3 sand circle test showed early loss of macrotexture and premature flushing after a new seal had been applied and failed the specified P/17 1-year texture loss performance criteria. Thus, the paper concludes that not only is having a quantitative metric essential to be able to accurately assess the performance of new seals but also that the use of the TNZ T/3 sand circle test furnishes an easy, cost-effective means to quantitatively characterize preseal surface texture.