Precision Study for Dynamic Modulus Testing of Asphalt Concrete Using Independent Assurance Testing

In this study, a precision study for dynamic modulus ($E^{*}$) testing is performed through independent assurance (IA) testing. The University of New Mexico (UNM) and AMEC Environment and Infrastructure, Inc. (AMEC) laboratories participated in this study. The precision and accuracy of the $E^{*}$ data are evaluated using $E^{*}$-trend plots, coefficient of variation (COV), within-laboratory consistency ($k$-statistic) plots, between-laboratory consistency ($h$-statistic) plots, one-way analysis of variance (ANOVA), and repeatability and reproducibility studies. The $E^{*}$-trend and mastercurve plots showed overlapping $E^{*}$ data at each temperature and loading frequency, suggesting no significant difference between the samples tested. Average COV values for UNM and AMEC laboratories were found to be 10 and 14%, respectively, which are acceptable for properly conducted testing. Average $k$-statistic values of $-0.3$ and 0.3 and average $h$-statistic values of 0.8 and 1.0 were found for UNM and AMEC laboratories, respectively, which indicated very good precision and accuracy. One-way ANOVA showed no significant difference between the means of UNM and AMEC test results. The average $E^{*}$ ranges for UNM and AMEC laboratories were determined to be 12 and 15, which are well below the repeatability and reproducibility limits. Based on the statistical analysis of the independent assurance test data, it can be concluded that $E^{*}$ testing is precise and accurate.