Effect of relative humidity on the linear viscoelastic properties of asphalt mixtures

Abstract It has been demonstrated that humidity, or water vapor, is a non-negligible contributor to moisture damage of asphalt pavements. However, little work has been done regarding the effect of humidity on the performance of asphalt mixtures. The objective of this paper was to investigate the linear viscoelastic (LVE) properties of asphalt mixtures under different humidity conditions. Specimens were first conditioned at four humidity levels and subsequently employed to perform dynamic modulus tests. Next, a shifting method for the master curve under humidity conditions was proposed to quantify the influence of water vapor on LVE properties of asphalt mixtures. Finally, the effect of humidity on LVE properties of asphalt mixtures was analyzed based on three aspects. The results show that the developed shift method is accurate enough to quantify the effect of humidity on master curves of asphalt mixtures since the error in any group is less than 2%, while each R2 value exceeds 0.98. The rheological parameter Ee decreases, and R and m increase as the humidity levels rise. However, no obvious variation trend was found in the Eg, k, and fc of different groups. The humidity factor g(Hi) shows a negative increasing trend based on the rise in humidity levels. Meanwhile, according to the developed three-dimensional master curves of dynamic modulus and phase angle of the two types of mixtures, dynamic modulus decreases and phase angle increases as humidity levels rise at low frequencies (or high temperatures). No significant differences were observed on dynamic modulus and phase angle among different groups at high frequencies. Thus, the developed three-dimensional dynamic modulus and phase angle master curves can determine dynamic modulus and phase angle under arbitrary humidity conditions.