Abstract
The dynamic modulus test is often adopted to characterize asphalt mixtures. The test results are used to compare asphalt mixtures’ resistance to deformation and serve as input for pavement performance predictions. American Association of State Highway and Transportation Officials (AASHTO) TP 132-19 provides guidelines on the test protocol required for small cylindrical specimens using the asphalt mixture pavement tester (AMPT), where significantly less material and testing time are needed compared with the standard for large cylindrical specimens (AASHTO T 378-17). Nonetheless, AASHTO TP 132-19 lacks repeatability and reproducibility limits for assessing the acceptability of test results. The study described in this paper presents the findings of an interlaboratory study (ILS) conducted to develop precision limits for AASHTO TP 132-19. Three mixtures and ten testing labs were involved in the experimental plan. Correlations were observed between dynamic modulus and both dynamic modulus coefficient of variation and phase angle standard deviation. Repeatability and reproducibility limits were proposed and defined as nonlinear functions of the dynamic modulus. The uncertainty in these nonlinear functional fits was incorporated into the proposed limits to help overcome limitations when assessing the test precision at various test determinations simultaneously. A novel mixture acceptance criterion was also proposed to help overcome the limitations from strict adherence to AASHTO T 378-17 while retaining the rigorousness of the statistics with marginal impact to pavement performance predictions.
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