Experimental Study on Chemical–Physical Hardening Mechanism of Early Strength of Filling Paste

The early strength of filling paste under sulfate solution immersion and creep conditions was analyzed by means of mechanical experiment, theoretical analysis and characterization of experiments. The chemical–physical hardening mechanism of initial strength of filling paste was obtained. Under the immersion of sulfate solution, a large amount of cementing material is formed inside the specimen, which increases the strength of the specimen. As the cementitious material fills the internal pore of the specimen, the strength of the specimen is reduced. According to the uniaxial compressive strength of the filling paste, the creep loading test was designed. Under the creep loading state, the filling paste strength showed the creep hardening characteristics, There are voids and voids in the internal structure of the filling paste specimen, and there is hardening phenomenon under creep conditions. The creep coefficient of saturated specimen is 1.174. Through NMR technology, the porosity of the specimen at the same loading stress level and different loading methods was quantitatively tested, and the compaction effect of creep loading on the gap inside the filling paste is the root cause of creep reinforcement.