Ultrasound-based freeze–thaw damage evaluation of graphene-basalt fiber asphalt mixtures

In this study, a unified calculation expression for freeze–thaw damage variables, including the ultrasound longitudinal wave velocity and void ratio, was derived based on the elastic wave theory to examine the properties of the freeze–thaw damage of graphene-basalt fiber asphalt mixtures. The method of evaluating the freeze–thaw damage of the asphalt mixtures based on non-destructive ultrasound technology was proposed and the freeze–thaw damage of graphene-basalt fiber asphalt mixtures was evaluated. The proposed method was validated and compared with an elastic-modulus-defined damage evaluation method. The results demonstrated that the proposed ultrasound-based freeze–thaw damage evaluation method applied to assess freeze–thaw damage of graphene-basalt fiber asphalt mixtures was viable and reliable, and freeze–thaw cycles have non-negligible impacts on the performance parameters of graphene-basalt fiber asphalt mixtures. As the number of freeze–thaw cycles increased, the ultrasound longitudinal wave speed and elastic modulus decreased progressively, and the void ratio gradually increased. Each of these quantities showed a large change amplitude initially and flattened out later. Moreover, the freeze–thaw damage of graphene-basalt fiber asphalt mixtures progressively increased as the number of freeze–thaw cycles increased. The largest increase occurred in the early stage of the freeze–thaw cycles, then gradually slowed down and basically reached a stable state after approximately 15 freeze–thaw cycles. The results of this study can be used as a theoretical basis and technical guide for the evaluation of freeze–thaw damage of graphene-basalt fiber and other asphalt mixtures in seasonally frozen areas.