Paired Measurement Strategy to Analyze the Effects of Construction Specification Changes on Quality of HMA Surface Courses (1877-5)

The primary objective was to develop and test a "Measurement Strategy" for evaluating the relative degree of success of new hot mix asphalt (HMA) pavement construction specifications using information from the Texas Department of Transportation (TxDOT) Pavement Management Information System (PMIS) database. The specific reason for developing a Measurement Stratagey was for use in comparing relative performance as a function of time of HMA pavements constructed under Item 340 with pavements constructed using the newer quality control/quality assurance (QC/QA) specifications. Researchers developed a paired analysis method and 30 pairs of pavements were identified to test the method. A paired set of pavements is defined herein as an Item 340 pavement and a QC/QA pavement that have similar locations, substrates, thicknesses, mixture type, and traffic but probably were constructed at different times by different contractors. Pavement performance information on these paired pavements from the TxDOT PMIS database was used in a statistical analysis in an attempt to determine which type of specification provided the best performing pavement. A second measurement strategy was developed and provided to TxDOT which uses a general analysis method; that is, it considers all the appropriate pavements in the PMIS database, even if the number of pavements prepared using the different specifications are unequal. The general approach is described in Research Report 1877-6. Even if pavements constructed using the different specifications performed differently, the PMIS data were found to be unsuitable for detecting these differences. Therefore, one of the chief benefits of this work was to determine and recommend the type of data that is necessary for TxDOT to fully implement the measurement strategy in the future.