Evaluation of Superpave Construction Quality on Low Volume Roads

Of the two million miles of asphalt pavement in the U.S., seventy percent experience low traffic. To utilize the latest technology on the bulk of the network, local agencies are expanding the use of Superpave to low volume roads. Superpave specifications are less restrictive in low volume applications to accommodate the use of local materials. The effects of relaxing these limits are widely unknown. There is a need to determine if the same level of quality is being achieved for Superpave mixes on low volume roads as their high volume counterparts. This paper investigates the effects of traffic level on construction quality. Compliance and variability are both evaluated for seven Superpave mixes, each serving different traffic levels. Quality assurance and quality control (QA/QC) data from over 550 Nebraska Superpave projects showed construction variability was significantly higher for low volume mixes. On average, nearly 100% more variability was found on low volume roads in coarse aggregate angularity (CAA) and 65% more variability in fine aggregate angularity (FAA) when compared to high volume mixes. Compliance, measured by percent within limits (PWL), was also significantly different among traffic levels. The overall PWL for low-level and high-level mixes was 78% and 90% respectively. Asphalt contents in low-level mixes were significantly higher than their targets, while high-level mixes showed no such trend. In addition, this paper briefly explores how the observed effects translated to early pavement performance. Results showed performance within the first two years was significantly lower when PWL fell below 85%. The need to address the issue of maintaining construction quality in Superpave implementation for low volume roads is presented