Research on fatigue performance of composite crumb rubber modified asphalt mixture under freeze thaw cycles

Abstract

To study the effect of freeze thaw cycles on the fatigue damage characteristics of composite crumb rubber modified asphalt mixture (CCRMA), the semicircle bending fatigue test and the digital speckle correlation method (DSCM) were combined and the fatigue damage characteristics of CCRMA and styrene–butadienestyrene-modified asphalt mixture (SBSMA) under freeze thaw cycles were analyzed. The plateau valve (PV) of the stiffness modulus degradation ratio curve of the asphalt mixture is proposed as the analysis index to evaluate the macroscopic fatigue damage evolution of the asphalt mixture. The horizontal strain density (DE value) obtained through analyzing the horizontal strain characteristic cloud map of the main crack zone is identified as an index to evaluate the mesoscopic fatigue damage evolution of the asphalt mixture. The results show that after a freeze thaw cycle, the PV increases, DE decreases, fatigue damage rate accelerates, and fatigue resistance decreases. CCRMA has better freeze thaw resistance and fatigue resistance than SBSMA. The fatigue damage model established has high fitting accuracy and can effectively reflect the fatigue damage evolution degree of an asphalt mixture. A correlation analysis of PV and DE values reveals that there is a good linear correlation between them, indicating that applying the DSCM method to semicircle bending fatigue tests for studying the fatigue damage characteristics of asphalt mixtures is reliable.