Quality Assurance Procedures for Chip Seal Operations Using Macrotexture Metrics

The Indiana Department of Transportation (INDOT) has implemented a comprehensive and proactive pavement preservation program to formalize preventive mainte­ nance activities such as thin surface treatments, crack seal, and chip seal (seal coat) and to determine the optimum balance between preventive maintenance ex­ penditures and capital expenditures. It is anticipated that in FYs 2017–21, INDOT’s six districts will altogether per­ form approximately 1,500 lane miles of chip seal work each year. It has been recognized that the quality of chip seal relies to a great extent on the qualities of binder and aggregate, proper application rate, construction, and existing pavement condition. To ensure successful chip seals, INDOT has implemented special quality assurance (QA) procedures, i.e., Activity 2050 Mainline Seal Coat Quality Assurance Evaluation (MSQA) that allows INDOT maintenance engineers to assess the quality of a new chip seal based on visual inspection of two 1,000-foot sections selected from a chip seal project.1 However, concerns associated with the MSQA pro­ cedures have been identified by INDOT maintenance engineers. First, the quality of visual inspection by hu­ man eye relies on the vision, experience, and level of training of the inspector. Issues may arise over the re­ liability and validity of visual inspection. Two randomly selected 1,000-foot-long sections may not fully represent the overall quality of the chip seal project. Second, each district usually performs approximately 250 lane miles of chip seal work every year, which may encompass ten to twenty different roads. INDOT is currently able to in ­ spect three to five roads per district per year. Third, visual inspection may become labor intensive, inefficient, and prone to errors as the current MSQA requires two visu­ al inspections performed, respectively, one month and