Assessments of mechanical responses of concrete deck pavement under moving truck load: Field strain measurements and modulus evaluation

Understanding mechanical responses of asphalt mixture layer under traffic load provides essential references for designing concrete deck pavement. The modulus is one of the critical input parameters for evaluating pavement responses of the asphalt layer. Laboratory experiments have traditionally been the main approach for determining the modulus of asphalt layers, overlooking potential discrepancies between the dynamic behaviors of asphalt layer obtained from laboratory testing and those occurring in actual field applications. Therefore, this research developed a full-scale experimental pavement section in which strain sensors were embedded to record field strain waveforms, thereby evaluating the mechanical responses of concrete deck pavement under moving truck load. Furthermore, the frequency and modulus of the asphalt layer in the field pavement were back-calculated. The determined field modulus was then compared with that measured in the laboratory to investigate their correlations. The results indicate that the loading frequency (f) acting on the asphalt layer under traffic loads tends to increase with higher vehicular speeds (v), and the relationship between f and v is determined as f= 0.165 v. Due to the visco-elastic behaviors, the measured critical strain of concrete deck pavement decreases with increasing loading frequency. The modulus measured in laboratory fails to simulate that determined via field tests and needs corrections. Specifically, correction factor for the SMA-13 asphalt layer was 0.86, while that for the AC-20 asphalt layer was 1.13. The research results are expected to guide the determination of asphalt layer modulus for concrete deck pavement evaluation and structure design.