Study on Early Hydration Mechanism of Double-Liquid Grouting Material Modified by Composite Early Strength Agent

Xinming Chen; Jie Wang; Huazhe Jiao; Zhi Yang; Diantao Zheng; Jinyu Sun

doi:10.3390/ma16196475

Study on Early Hydration Mechanism of Double-Liquid Grouting Material Modified by Composite Early Strength Agent

Materials (Basel). 2023 Sep 29;16(19):6475. doi: 10.3390/ma16196475.

Authors

Xinming Chen^{1

2}, Jie Wang^{1

2}, Huazhe Jiao^{1

2}, Zhi Yang^{1

2}, Diantao Zheng^{1

2}, Jinyu Sun^{1

2}

Affiliations

¹ Henan Key Laboratory of Underground Engineering and Disaster Prevention and Control, Henan Polytechnic University, Jiaozuo 454150, China.
² College of Civil Engineering, Henan Polytechnic University, Jiaozuo 454150, China.

Abstract

To achieve an adjustable setting time and significantly improved early strength of a new type of sulphoaluminate cement-based double-liquid grouting material (SACDL), the effects of calcium formate, sodium sulfate, lithium carbonate, and a composite early strength agent on the setting hardening and early hydration behavior of SACDL paste were studied by means of setting time, fluidity, compressive strength, and viscosity tests. The results showed that the adsorption and osmosis of calcium formate, the complex decomposition of sodium sulfate, the precipitation polarization of lithium carbonate and the synergistic action of the composite early strength agent could accelerate the early hydration rate of SACDL, shorten the coagulation time, and improve the early strength of SACDL. The composite effect of 0.8% calcium formate and 0.5% sodium sulfate is the most significant in promoting coagulation and early strength; the initial setting time and final setting time of the slurry were shortened to 5 min and 10 min, respectively; and the 3 h compressive strength was capable of reaching 16.7 MPa, 31% higher than that of the blank group. In addition, X-ray diffraction and SEM morphology observation were used to study the composition of the hydration products and the evolution of the microstructure, which revealed the early hydration mechanism of SACDL under the synergistic effect of the composite early strength agent: (1) The solubility of tricalcium aluminate (C₃A) and dihydrate gypsum (CaSO₄·2H₂O) increased under the low content composite early strength agent condition, which increased the ettringite (AFt) formation rate. HCOO^- was able to penetrate the hydration layers of tricalcium silicate (C₃S) and dicalcium silicate (C₂S), accelerating the dissolution of C₃S and C₂S and promoting the early hydration of SACDL. (2) Under the condition of a high dosage of the composite early strength agent, the further increase in Ca²⁺ concentration promoted the crystallization nodules and precipitation of CH and accelerated the formation of calcium silicate hydrate (C-S-H) gel. C-S-H was filled between a large number of rod-like AFt crystals, thus making the structure more dense.

Keywords: calcium formate; early strength agent; grouting material; hydration mechanism; lithium carbonate; sodium sulfate.

Grants and funding

This work was supported by the double first-class construction of safety discipline of Henan Polytechnic University (AQ202300401), and the key scientific and technological project of Henan Province (222102220019).