الفهرس | Only 14 pages are availabe for public view |
Abstract Reusing asphalt pavement (RAP) has been utilized in producing new bituminous mixes for last several years and has turned into a popular topic in pavement organizations. However, worries from its behavior in the field have been still standing. The main objective of this research is investigating the long-term performance of asphalt overlays containing RAP in flexible pavement rehabilitation using data from Long Term Pavement Performance (LTPP) program. Many variables are considered such as overlay thickness (51, 127mm), asphalt overlay materials (virgin mixtures compared with mixtures including 30% RAP), climate (wet, dry) and pre-overlay curing that means pavement surface handling before rehabilitation by low or heavy grinding. In this study, data from 6 sites are taken to perform analysis where each site consists of 8 sections (4 sections with virgin materials and another 4 sections using 30%RAP). These sites are selected due to their similar climate to Egypt. Five performance indicators are chosen including fatigue cracking, longitudinal cracking, transverse cracking, rutting, and roughness. Four statistical analyses are performed on extracted data to determine the priority in performance and the significance in variation. The first analysis is plotting the extracted data for each investigated parameter on one graph to illustrate the potential variation. In order to assess the development of performance, significant performance indicators are generated versus time. The second analysis is using paired t-tests and p-values. The third analysis is the analysis of variance (ANOVA) while the fourth analysis is the Friedman test. The results of field observations indicate that the RAP sections achieve similar/ better performance as compared with virgin sections except for rutting development which increased at using RAP. Moreover, RAP addition in thicker overlay provides lower fatigue cracking progress while thinner overlay for RAP sections provides lower longitudinal cracking development. The pre-overlay handling doesn’t appear any noticeable difference in fatigue, longitudinal and transverse cracking development. The climate has no obvious effect on fatigue and transverse cracking progress while dry climate provides higher longitudinal cracking and roughness progress for RAP sections. Statically, the variation in pre-overlay curing (from low to heavy) has the highest statistical effect on fatigue and transverse cracking, while rutting and roughness progresses aren’t clearly affected by variation in climate, thickness or surface curing before rehabilitation. According to ANOVA test, the variation in climate from wet to dry has a significant statistical effect on reducing fatigue cracking and increasing longitudinal cracking. For the Friedman test, the best performance is for the thicker overlay against fatigue cracking, rutting, and roughness. Heavy preoverlay curing has the lowest ranks especially with 127-mm thickness against fatigue cracking, rutting, and roughness. Low grinding and 51-mm thickness are the best opportunity for RAP sections against both of longitudinal and transverse cracking. |