In current construction practice, as-built asphalt concrete acceptance istypically based upon several key quality assurance/quality control (QA/QC) parameters. These parameters have pay factors that are empirically established by judgment of the pavement community. The pay factor has been used to reward/penalize the contractor for the construction quality. These properties are known to influence pavement performance, the specific effect upon performance and project life has been impossible to estimate. Because of this, there is an urgent need to tie deviations from the job-mix and correlate them to pavement life. This research focused upon the integration of the mechanistic-empirical pavement design guide (MEPDG) (NCHRP1-37Aand NCHRP1-40) with the Simple Performance Test (NCHRP9-19) to develop a probabilistic Quality Specifications for Quality Assurance of HMA Construction. This has been the major objective of NCHRP9-22. The methodology is based on relating the HMA dynamic modulus, through a closed form solution,to major pavement distress. A Monte-Carlo simulation is run using the project mix design to predict the as-design distress and its associated variability. The as-design distress is then used to predict the remaining service life of the pavement. Similarly, a Monte-Carlo simulation is run for the as-built material to estimate the remaining service life. The difference between the as-built and as-design provides the predicted difference in quality of construction from mix-design. The difference is used to calculate the pay factor for each distress. The summation of the pay factors yields the total pay factor for the project. Finally the initial international reference index (IRI) representing the ride quality pay factor is added.
Samenvatting