Effectiveness of Maintenance Treatments of Flexible Pavements

To achieve effective pavement maintenance, the life expectancy and timing of treatment applications need to be determined. The Long Term Pavement Performance (LTPP) program includes the Specific Pavement Study-3 (SPS-3), which focuses on this subject. The treatments applied are chip seals, crack seals, slurry seals, and thin overlays. In studying the life expectancy it is not feasible to wait for all the sections in the experiment to fail. Thus, there is a need to determine the life expectancy while making efficient use of the available data collection funds. Survival data analysis is a statistical technique that meets this need by accounting for the portion of the sections in which the exact time the treatment lasted is not known. The application of this technique to flexible-pavement maintenance is presented. In addition, some results of the LTPP SPS-3 experiment are presented to the highway community. The focus is on the LTPP Southern Region. The results showed that the probability of failure was two to four times higher for the sections that were in poor condition at the time the treatment was applied than those sections that were in better condition. The median survival times for thin overlays, slurry seals, and crack seals were 7, 5.5, and 5 years, respectively. The chip-seal sections had not yet reached the 50 percent failure probability after 8 years of the SPS-3 experiment. Accordingly, chip seals appear to have outperformed the other treatments investigated in this study in delaying the reappearance of distress.