Assessment of the TxDOT Binder Quality Assurance Program

Most state departments of transportation (DOTs) maintain asphalt binder quality assurance (QA) programs to ensure that asphalt binders used in the construction of their road system meet specifications stipulated for each project. The Texas Department of Transportation (TxDOT) samples and approves asphalt materials at the source and utilizes these materials in highway projects without consideration of possible changes in properties that may occur between production and use during construction. Historic concern and limited recent data indicate that binder properties do change, contributing to difficulties during construction operations and poor performance. The primary goal of this project was to evaluate the current TxDOT binder QA program and recommend revisions as necessary toward improving quality. This final report documents an assessment of the current program based on (1) an extensive information search and review that included two detailed surveys of TxDOT districts and nine other state DOTs and (2) results from a comprehensive laboratory testing program that simulated factors that may affect changes in binder properties prior to use. Recommendations for improvement are provided, and these recommendations are evaluated in terms of resource requirements. In a recommended total binder quality system, the binder QA program would be one tool to improve material quality used during construction. Other recommended tools include mandated quality control (QC) plans for both suppliers and contractors that require special handling for binders, training programs for sampling and testing, general education seminars presenting the goals of the system to all involved, and a round-robin program to establish testing variability. Development of a user-friendly database for storing binder QA data that includes storage times, storage temperatures, and pavement performance data is also recommended with a suggetion of frequent analysis of this data, possibly to set frequency rates for field sampling by binder and supplier.