Lessons Learned from the Long-Term Pavement Performance Program and Several Recycled Sections in Texas

摘要

The performance of recycled asphalt pavement (RAP), the effects of milling, and overlay thickness are important factors for pavement engineers to consider when making decisions on rehabilitation and maintenance activities. Specific Pavement Studies- (SPS-) 5 sections were built 10 years ago to address this issue. Performance data under well-documented SPS sections has provided valuable insight that could not have been achieved otherwise. SPS-3, SPS-5, and three hot-in-place (HIP) recycled sections were studied. One of the HEP recycled sections was adjacent to an SPS-3 and a SPS-5 section, thus they all possessed the same underlying subsurface layers. It was found that after more than 10 years of service, the RAP sections perform as well as the virgin asphalt concrete (AC) sections. This indicates that the RAP can be effective when used properly. Also, little difference was found in terms of performance on milled and non-milled sections. However, to date, there is less distress on the 125-mni sections than 50-mm sections. It is important to note that all SPS-5 sections are able to resist reflective cracking when a mixture of 30% RAP and a softer binder is used, the result is a high penetration number (30 to 45), with a flexible mixture able to resist cracking In contrast, cracks came through the HEP recycled sections in just a few weeks for US-175 and US-84. Low penetration numbers in the range of 20 to 21 were found. A 75% mixture of RAP was found to be too high, because aged binder tends to become brittle, and consequently does a poor job resisting cracking. The HEP recycled process was used satisfactorily on US-281 where no cracking potential existed. Thus, concluding that high percentage RAP mixture should not be used on any location where cracking potential is present Also, a lower viscosity AC should be added to the RAP to increase the flexibility. The results in the SPS-3 sections indicated that chip seal is the most cost-effective, preventive maintenance (PM) treatment Although rehabilitation strategy on SPS-5 sections cost more than PM treatments on SPS-3 sections, SPS-5 sections performed better than the SPS-3 sections. The most important factor influencing pavement performance on SPS-3, SPS-5, and HIP recycled sections is these types of surface AC treatments.