Study on crack resistance of basalt fiber reinforced asphalt mixture modified by titanate coupling agent based on digital image correlation

Basalt fiber is widely used in pavement engineering for its strong mechanical properties, while its smooth surface can cause it to slip within the asphalt mixture, weakening the overall structure. In addressing this issue, this study explores the application of a titanate coupling agent (TCA) for surface treatment of the fibers. The aim was to enhance the interfacial adhesion between the fiber and the asphalt, consequently improving the crack resistance of the fiber-asphalt mixture. This study delves into the modification mechanism and chemical grafting process of TCA, employing scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Furthermore, digital image correlation (DIC) was utilized to dynamically monitor the semicircular bending test (SCB) specimens under full loading conditions, facilitating a comprehensive evaluation of the damage evolution process. Through comparative analyses of load-displacement profiles, full-field strain, displacement, and crack development, alongside the characterization of the fracture process zone (FPZ), a multiscale quantitative assessment was conducted on the cracking characteristics of the asphalt mixtures. Throughout the damage evolution process, the toughening and crack-blocking effects of the modified fibers were extensively evaluated. Concurrently, SEM was employed to observe the fiber distribution and microscopic morphology of the fracture surface, shedding light on the mechanism of action of TBF (Treated basalt fiber) from a microscopic perspective. The augmentation of TBFAM (Treated basalt fiber Asphalt Mixture) is systematically elucidated, demonstrating that, in comparison with the other two asphalt mixtures, TBFAM exhibits prolonged microcrack formation time and a slower rate of crack propagation. The strain at the crack initiation point increased by 1.45 %, with a concurrent 2.49 % increase in the high strain area, indicative of its superior crack resistance. TCA facilitates the generation of a biomimetic coating via chemical grafting, thereby enhancing the surface structure of basalt fibers and fortifying the fiber-asphalt interface bonding ability. The favorable surface structure of TBF fosters a three-dimensional network within the asphalt mixture system, offering functionalities such as bridging, adsorption, toughening, and crack prevention. This impedes crack development and further bolsters the stability of TBFAM.