Experimental investigation and theoretical analysis of long-term performance for optical fiber Bragg grating-fiber reinforced composite in alkaline concrete environment

Fiber reinforced composite (FRP) is a promising material to encapsulate optical fiber Bragg grating sensors for in-situ structural monitoring and reinforcement. However, the long-term performance of multifunctional optical fiber Bragg grating-basalt fiber reinforced polymer (OFBG-BFRP) in concrete structures remains unclear. Hence, its mechanical and sensing properties under alkaline concrete condition were experimentally investigated and theoretically analyzed. The results showed that the tensile strength and strain sensing range of OFBG-BFRP decreased by 22 % and 43 % under alkaline concrete condition, respectively. The relationship between the elastic modulus and sensing sensitivity was significant with 0.77 Person correlation coefficient. It is revealed that, for OFBG-BFRP bar, the sensing performance degradation in alkaline concrete condition was mainly caused by optical fiber-resin interfacial debonding, while the mechanical deterioration was attributed to resin hydrolysis and basalt fiber-resin interfacial debonding. Based on the deterioration mechanism and chemical etching theory, a service life prediction model is proposed to evaluate the performance of OFBG-BFRP accurately. This work facilitates in-depth understanding on the deterioration behavior and mechanism of OFBG-BFRP bars in concrete structures, inspiring accurate service life prediction for safe and durable FRP reinforced concrete structures.