In situ continuous decoding of temperature humidity and micro strain during sandstone fracture hole restoration

Abstract To investigate sodium silicate slurry curing mechanisms and sandstone interactions during crack restoration, an in-situ fiber Bragg grating (FBG) sensor system was established to monitor temperature, humidity, and micro-strain during curing. The surface morphology and material composition of sodium silicate slurry at different temperatures were also investigated. The results indicated that CH 3 COOH from CH 3 COOCH 2 CH 2 OOCCH 3 hydrolysis reacted with Na 2 O • nSiO 2 , generating heat (max heating rate: 0.42 °C/h at 35 °C), reducing humidity (max dehumidification rate: 0.79% RH/h at 35 °C), and inducing shrinkage strain (peak at −115.23 με at 35 °C). The grout achieved optimal curing, forming a densified structure with small CH 3 COONa migration, inducing only 31.62 με micro-strain on the sandstone surface at 35 °C. Smaller fissures reduced sandstone strain and damage, confirming sodium silicate is more suitable for small fissures at 35 °C. This study advances heritage conservation and fiber optic sensing via intelligent relic preservation technologies.