Study on expansion effect and hydration characteristics of ultra-high strength cement-based grouting materials based on humidity compensation

Abstract

The combination of superabsorbent polymer (SAP) and expansive agent can effectively reduce the shrinkage deformation of ultra-high strength cement-based grouting materials (UHS-CGM) in dry environment. However, there are differences in the compensation shrinkage mechanism of SAP and expansive agent, and the presence of SAP may have adverse effects on the working and mechanical properties of grouting materials. In order to evaluate the synergistic effect of SAP with different water adsorption and release characteristics and MgO expansion agent (MEA), the influence of different SAP size and dosage on the compressive strength, restrained expansion rate, internal relative humidity (IRH) and hydration characteristics of UHS-CGM containing MEA were investigated, and then the composition and content of hydration products were analyzed by TG and XRD, the microstructures were observed by SEM in this paper. The results show that SAP improved the hydration degree of UHS-CGM and the expansion efficiency of MEA, and significantly increased the restrained expansion rate of UHS-CGM under standard curing and sealed curing, while reduced the compressive strength of UHS-CGM, and the decreasing degree was aggravated with increasing size and dosage of SAP. Overall, small size SAP has better inner curing efficiency and compensates shrinkage effect.