Development of time-temperature-humidity superposition principle for asphalt mixtures

Variation of the humidity in asphalt layers may very likely induce change in the viscoelastic properties of asphalt mixtures. It has been the authors' speculation that humidity is an important factor in the properties of asphalt mixtures, just like temperature. However, it has not been reported in the literature regarding how humidity influences the viscoelastic properties of asphalt mixtures. This study developed a time-temperature-humidity superposition principle for asphalt mixtures and established temperature-humidity correspondence. The magnitude of the complex modulus vertical bar E*vertical bar and the phase angle of the complex modulus. of typical asphalt mixtures were measured at a number of combinations of temperatures and humidity levels, and the humidity-dependency of the viscoelastic properties of asphalt mixtures was identified. The time-temperature-humidity shift factor was derived for the construction of master curves of vertical bar E*vertical bar and. at the reference state. The goodness of model fit validated the developed time-temperature-humidity superposition principle. The equivalent effect of humidity on vertical bar E*vertical bar and. was evaluated with respect to temperature. This study demonstrated the significant effect of humidity on the viscoelastic properties of asphalt mixtures. The developed time-temperature-humidity superposition principle is important in determining the timedependent and humidity-dependent viscoelastic properties of asphalt mixtures from known properties at a reference temperature and a reference humidity.