Development of thermal resistant stone mastic asphalt mixtures for permafrost regions

To reduce heat absorption and accumulation in asphalt pavements for permafrost highways, a thermal resistant stone mastic asphalt mixture (TRSMA) was developed by partially substitute basalt aggregates in the stone mastic asphalt mixture (SMA) with calcined bauxite (CB) aggregates. Image processing and analysis methods were employed to quantify the distribution of CB aggregates in TRSMA. Thermal conductivity test, wheel tracking test, and moisture sensitivity test were conducted to evaluate the influences of CB content (20 %, 40 %, 60 %, and 80 % based on 5-10 mm basalt) on the thermal conductivity, rutting resistance, and moisture sensitivity of TRSMA. Results demonstrated that as the CB content increased, the thermal conductivity of TRSMA decreased. Compared to SMA-13, TRSMA-20, TRSMA-40, TRSMA-60, and TRSMA-80 exhibited reductions in thermal conductivity coefficient by 15.0 %, 38.2 %, 45.7 %, and 50.5 %, while the materials cost increased by 4.2 %, 6.6 %, 9.4 %, and 13.6 %, respectively. Williamson's model proved to be the most effective in predicting the thermal conductivity of TRSMA. The rutting resistance of TRSMA-40, TRSMA-60, and TRSMA-80 improved with increasing CB content. TRSMA-60 is recommended as the optimal mixture considering heat resistance, rutting resistance, moisture sensitivity, and cost. Field tests revealed a maximum temperature reduction of 6.2 degrees C at the bottom of the TRSMA-60 layer and a delayed time to reach its peak temperature.