Evaluation of the residual fatigue life of semi-rigid base course of existing freeway using the SCB and FWD test

Lime-fly ash treated (LAT) material, as a semi-rigid base course (SRBC) material applied to freeway construction in China, has been widely used since the late 1990s. Currently, many of these road sections are approaching or surpassing their designed service life and are undergoing reconstruction and expansion. Therefore, this paper aims to propose a method for evaluating the fatigue resistance of LAT SRBC utilizing semi-circular bending (SCB) and falling weight deflectometer (FWD) tests. Based on the regression equations established between Rc and SCB tensile strength, along with the results of the SCB fatigue and field FWD tests, a fatigue model for the SRBC structure was developed using Rc and FWD deflection difference (D20-D60) as parameters. Results indicated that the fatigue life of the LAT SRBC of road sections A, B, C and D was 6.496×10^10, 2.541×10^10, 6.569×10^10, and 5.378×10^10, respectively, while the fatigue life calculated by the SCB tensile strength and the calculated values of the bottom tensile stress parameters was 6.247×10^10, 2.743×10^10, 6.944×10^10, and 4.983×10^10, respectively, which implied that established fatigue model effectively enabled the assessment of the residual fatigue life of LAT SRBC of the existing freeway.