Time-Temperature Superposition for HMA with Growing Damage and Permanent Strain in Confined Tension and Compression

The objective of this paper is to verify the time-temperature superposition (t-TS) principle for hot-mix asphalt (HMA) with growing damage and permanent strain at different confining pressures in both the tension and compression stress states. Dynamic modulus tests at various confining pressures were conducted both in tension compression and in compression. The results were investigated to evaluate the effects of confining pressure and stress on the thermorheological simplicity of HMA within the linear viscoelastic range. Constant crosshead rate tests, both in tension and in compression, and repetitive creep and recovery tests in compression were also performed to check the t-TS principle with growing damage and permanent strain level with regard to the effects of confining pressure and stress. The analysis results show that the HMA remains thermorheologically simple regardless of stress state, damage, and permanent strain level under the same confining pressure. However, confining pressure does have an effect on the dynamic modulus and shift factor, especially at a high temperature and/or low reduced frequency.