<p><p><strong>References:<br></strong><em>Al-Qadi and Appea (2003)<br>Black and Holtz (1999)<br>Hayden et al. (1998)<br>Loulizi et al. (1999)</em></p><p><strong>Method Summary </strong></p><p>A nondestructive FWD test is conducted on the pavement to estimate its structural capacity and thus its service life. The FWD equipment can apply an impulse load of 40 kN for 40 ms to simulate the traffic load on the pavement. The deflection data obtained is used to calculate the resilient moduli of the pavement layers using the back-analysis. MODULUS Version 5.0 and ELMOD programs are used for the FWD data analysis. In MODULUS, the resilient moduli of the HMA and aggregate base layers obtained in the laboratory simulating the field conditions at the time of FWD testing are fixed and the subgrade modulus is obtained by iterative back-calculations. In ELMOD, the moduli of the HMA and subgrade layers are fixed and the resilient modulus of the base layer is back-calculated. The temperature correction model developed from statistical analysis of the measured deflections and HMA mid-depth temperatures was applied to the study. The thickness of HMA used for the temperature correction model is obtained by direct measurement of the thickness of the HMA through field cores. The results of Surface Curvature Index (SCI) and Base Damage Index (BDI) for all nine sections are collected during an eight-year period and then are analyzed and corrected to a standard temperature of 25°C. The resilient moduli of the pavement layers obtained using the FWD testing are utilized to calculate the vertical compressive stress using the mechanistic approach. The stress developed under the HMA pavement surface is correlated with the rate of rutting.</p><p><strong>Accuracy and Precision</strong></p><p>The resilient moduli of the pavement layers were obtained using back-analysis. Resilient modulus is used as a design input for both the empirical and mechanistic-empirical design methods. The back-calculated modulus can be accurate if the moduli of other layers are known, but the analysis procedure does not often give the unique solution if the moduli of other layers are unknown.</p><p><strong>Adequacy of Coverage</strong></p><p>FWD data can be used to determine the resilient moduli of the pavement layers and rutting rate to estimate the structural capacity and the service life of the pavement. The pavement condition can be evaluated using a reasonable number of FWD tests. Adequacy of coverage depends on the frequency of tests.</p><p><strong>Implementation Requirements </strong></p><p>This method requires a correction for temperature and assumes the moduli of any two layers simulating the same conditions at the time of FWD testing. Therefore, the implementation requirements are somewhat greater than desired.</p><p><strong>General Comments</strong></p><p>The FWD test is a common, easy to implement method of testing. It is typically used for quality assurance and evaluating completed pavement sections. This test is used to verify assumed stiffness, monitor performance over time, and to compare the sections with geosynthetics to control pavement systems.</p></p>