ROUND 1 TYPE I UNBOUND GRANULAR BASE COURSE PROFICIENCY SAMPLE PROGRAM

Strategic Highway Research Program (SHRP) Protocol 46, "Resilient Modulus of Unbound Granular Base/Subbase Materials and Subgrade Soils", was the specified procedure for laboratories performing resilient modulus tests on research samples of unbound granular base course material obtained from Long-Term Pavement Performance (LTPP) field sites. P46 requires a test system that includes a triaxial pressure cell component, a closed loop electro-hydraulic repeated load component, and certain load and specimen response control, measurement, and recording components. Two elements of P46 testing were particularly important: verification that the system was calibrated and yielding reasonable results and a practical means of performing quality checks on a daily or more frequent basis. A set of eight test samples was shipped to each of nine LTPP laboratories with appropriate instructions. All participants were required to complete testing of Type I synthetic reference sample set prior to testing the Round 1 proficiency samples. Worksheets, supporting data, analyses, final comments, and conclusions are presented.