Crack monitoring of asphalt mixtures via embedded ultra-weak fiber Bragg grating

Cracks are a common and critical form of damage in expressway structures, where asphalt mixture serves as the primary surface layer material. However, the cracking response of ultra-weak fiber Bragg grating (UWFBG) sensors in asphalt mixture remains ambiguous, limiting their practical application in road monitoring. This paper explores the crack response characteristics of UWFBG sensors to enable effective crack detection in asphalt mixtures using crack, cutting experiment, and numerical analysis. The numerical results show that the mortar-UWFBG interface is the weakest region within the asphalt mixture. The experimental results show that these UWFBG sensors can quantitatively measure cracks with widths ranging from 0.46 to 5.75 mm, exhibiting a strong linear correlation between wavelength and actual crack width, which agrees with the numerical analysis results. Furthermore, the experimental results show that they are capable of detecting cracks as narrow as 0.5 mm. This work provides a reliable approach and insight for crack development of asphalt mixture with embedded UWFBG sensing cable in road infrastructure.