The deterioration and performance improvement of long-term mechanical properties of warm-mix asphalt mixtures under special environmental conditions

To analyze the long-term influence of different climatic conditions such as continuous high temperature, seasonal freezing, tropical rain climate, salty and humid environments on mechanical properties of warm mix asphalt (WMA) mixtures, various simulated methods and time periods were used to simulate climatic factors' influences on the performance deterioration of WMA mixtures in the laboratory. The volume of air voids (VV), splitting tensile strength (STS) and strength loss rate were used to evaluate the performance change of the mixture, the influencing degree of the four climatic factors was discussed, and the strength difference between WMA and HMA mixtures was analyzed. Besides the improvement of various materials like asphalt, fiber, hydrated lime and cement on mechanical properties were also studied. The results show that the VV of Sasobit-WMA mixtures gradually increases and STS decreases in different environments for a long time, and the influence of these climatic factors on the VV and STS of mixtures are expressed as follows: freeze thawing, tropical rain climate, salty and humid environment, high temperature; the VV and STS of Sasobit-WMA mixtures are approximately stable after the asphalt mixtures suffering 15 freeze-thaw cycles, 12 continuous soaking cycles, 12dry-wet cycles in salt solution, 12 thermo-cycling in high temperature; and the long-term mechanical properties of WMA are inferior to HMA mixtures in these environmental. Among selected WMA mixtures, the mechanical property of Asph-WMA mixtures is worst. The fibers are better than hydrated lime and cement in improving mechanical properties in special environments.