Subsurface Condition Evaluation of Asphalt Pavement for Pavement Preservation Treatments

This paper introduces a guideline for evaluating the asphalt pavement subsurface condition, developed by Indiana Department of Transportation to determine the applicability of pavement preservation treatments (PPTs). The evaluation procedure consists of four major steps, including site selection, preliminary assessment, data collection/test, and analysis. The guideline has hierarchal evaluation level based on type of data available for the test section. Level 1 is selected if Ground Penetration Radar (GPR) analysis data is available and Level 2 is selected if surface distress data is available. Level 3 is used for all other cases. A case study was conducted on the SR-70 section with microsurface treatment for understanding its subsurface condition and validating the evaluation methods. The level 1 evaluation with GPR on the SR-70 test section determined that 20.5% of the test section length contained the problem locations with the fair subsurface condition and the rest 79.5 % of the length had the good subsurface condition. Similarly, 28% of the test section length with was determined to have the fair subsurface condition by the level 2 evaluation with surface distress. The rest 72% of the test section without surface distresses was estimated to have the good subsurface condition. In addition, the PPT applicability on SR-70 test section was determined. Considering the subsurface distress distribution analysis using distress coverage of unit analysis length (DUCAL), the test section was determined to be inadequate for the PPT application. Conclusively, the case study confirms that the evaluation processes are applicable and can help a consistent and rational decision making process for project level or district level pavement preservation program. Two softwares were developed as tools to aid the user in utilizing the guideline more effectively and conveniently. “INDOT Pavement Subsurface Condition Evaluation (iSub)” is entirely based on the “Guidelines of subsurface condition evaluation for pavement preservation.” Thus, iSub provides user-friendly system which helps to follow the hierarchy of evaluation steps. Furthermore, iSub automatically calculates the overall condition of the pavement subsurface as severity rating for each laboratory test result was implemented into the software. The other software “INDOT Water Stripping Severity Evaluation (iMoisture)” was developed to aid the water stripping severity evaluation of INDOT subsurface condition evaluation process. iMoisture detects uncoated aggregates and quantifies the area in a sample by employing the digital image analysis technology.