Differentiation and quantification of interlayer fatigue shear resistance between double-layer composite asphalt mixtures under complex coupled pavement working conditions

In order to quantify the interlayer shear fatigue performance between the upper-middle layer composite materials in asphalt pavement structure under complex coupled pavement working conditions (such as temperature, axle weight, vehicle speed, acceleration, road slope, etc), this study proposes a novel fatigue test method (Dynamic Phase-Transition Test Method). Using this method, extensive tests were conducted on the interlayer fatigue shear resistance between double-layer SBS modified asphalt mixtures (SMA-13/AC-16). Differentiation and quantification of interlayer fatigue shear resistance under complex coupled pavement working conditions were carried out. The main conclusions are as follows: compared to traditional fatigue testing methods, the DPT Test method reduces the test workload by 89 % while yielding results with lower variability. The quantitative model for interlayer shear fatigue life Nf, developed from DPT testing results, accurately predicts interlayer fatigue performance under complex coupled road conditions. In comparison to general working conditions (20 degrees C, 0.5 MPa, 45 km/h, 0.0 G, 0 %), the interlayer shear fatigue life Nf decreases by 90 % under high-temperature heavy-load conditions (50 degrees C, 0.7 MPa, 45 km/h), by 96.3 % under high-temperature, heavy-load, low-speed conditions (50 degrees C, 0.7 MPa, 20 km/h), by 99.7 % under extreme conditions of heavy-load vehicle acceleration (50 degrees C, 0.7 MPa, 8 km/h, 0.4 G), and by 99.0 % during extreme conditions of heavy-load vehicle braking downhill at low speed (50 degrees C, 0.7 MPa, 21 km/h, 0.3 G, 9 %). The research findings provide a reference for the specific degree of interlayer fatigue performance decay of upper-middle layer composite materials (SMA-13/AC-16) under complex coupled pavement working conditions.