摘要: |
Two experiments are included within the Long Term Pavement Performance (LTPP) program to provide data on the performance of rehabilitated asphalt concrete (AC) pavements. These two experiments include Specific Pavement Studies No. 5 (SPS-5) and GeneralPavement Studies No. 6 (GPS-6). The SPS-5 experiment was developed to study the performance of AC overlays of existing AC pavements and includes nine test sections per project The GPS experiment was designed to monitor test sections selected from existing pavements that were nominated by State Highway Agencies (SHAs).
This report summarizes the performance trends and initial observations of the 17 SPS-5 projects and the 125 GPS-6 test sections. !' provides results that can be used in making tehabilitation decisions. The primary approach adopted was the development of graphs of performance indicators (or distress types) versus time. These performance indicators included fatigue cracking, longitudinal cracking within the wheel path and outside the wheel path, transverse cracking rutting, and roughness. The analyses were made to evaluate the effects of the different experimental factors included within the SPS-5 and GPS-6 experiments on performance. These analyses and summaries were related to the effect of overlay thickness, the effects of milling, and the effects of mixture type on performance. The following provides an overall summary of the findings related to the three primary factors included in the experiment
• The nominal 127-mm overlays have generally performed better than the nominal 51-mm overlays, as expected. The thicker overlays generally exhibited less cracking distress than the thinner ones, but had little effect on the occurrence of rutting and no apparent effect on • The test sections that had been milled prior to placement of the overlays generally have performed better than those test sections that were not milled. Although there are exceptions to these findings, less fatigue cracking, longitudinal cracking within the wheel paths, and transverse cracking were observed on the sections that had been milled. No substantial difference was noted between longitudinal cracking outside the wheel paths, rutting, and roughness between the test sections with and without milling.
• The different type of mixtures (virgin or recycled asphalt concrete mixtures) appeared to have the least effect on performance of any of the factors included in this experiment. However, for those sites where there was a difference, the virgin mixtures generally performed slightly better than the recycled concrete mixtures.
• More importantly, the results and findings from this initial evaluation suggest that there will be sufficient data in time to support development of the expected products from these experiments, and development and calibration of the AASHTO 2002 Mechanistic- Empirical Design Guide, as well as other rehabilitation design procedures.
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