Volume 38, Issue 4 (July 2010)
Lessons Learned from RAP Sections with 17 Years of Service
Maintenance and rehabilitation (M&R) play a key role in maintaining aging highway infrastructures. Asphalt concrete (AC) overlays have been widely used in M&R across the state. The successful application of an AC overlay requires comprehensive and in-depth knowledge regarding its material characteristics and in situ performance. To better understand the AC overlay’s behavior, the Texas SPS-5 sections from the Long-Term Pavement Performance program are investigated in this study. The eight test sections perform satisfactorily even after 17 years of service. The purpose of this study is to extract useful information and propagate this success to similar rehabilitation projects. The study includes two aspects of work complementary to each other: (A) Laboratory material properties testing (binder and aggregate tests, overlay tester test, and the Hamburg wheel track test) and (B) in situ pavement performance evaluation (transverse cracking, reflective cracking, rut depth, and ride quality). By integrating the information from both aspects, the findings are given as follows: (1) AC overlay with 35 % reclaimed asphalt pavement (RAP) can perform well if properly designed and constructed; (2) in terms of resisting reflective cracking 1 unit thick of 35 % RAP is equivalent to 0.26 unit thick virgin mixture; (3) with the 40 % reflective cracking rate criterion, the life for virgin AC with a 125 mm overlay is 65 % longer than that for a 50 mm overlay; (4) in terms of pavement performance, no significant difference exists between 50 mm milling and non-milling if the milling does not remove existing cracks completely; (5) the maximum rut depth of 12.7 mm among the test sections indicates that the mixture is rut-resistant, and the existing pavement with lime-treated base and subbase beneath the overlay provides sound foundation; and (6) the overlay tester can be a viable and simple measure to evaluate the asphalt mixtures’ reflective cracking resistance.