Effects of various gypsum on early-age hydration behavior of magnesium oxychloride cement (MOC)

Ma, Cong; Feng, Shuming; Zhang, Zedi; Chen, Gege; Shi, Jinyan; Song, Danqing; Zhou, Haijun; Dong, Biqin; Du, Yanliang

doi:10.1007/s10973-023-11983-y

Cited by 7 publications

(1 citation statement)

References 30 publications

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“…The viscosity and temperature of the slurry increased and then decreased with the increase in sodium sulfate doping, and the viscosity and temperature of the slurry peak increased significantly, which was due to the hydration of quicklime and slaked lime in the ethanol to increase the concentration of CH in the liquid phase. This prompted a reaction between sodium sulfate and CH to generate CaSO 4 with very high activity, thus accelerating the generation rate of CaSO 4 •2H 2 O colloidal particles and causing the viscosity and temperature of the slurry to increase rapidly [39,40]. When the dosage of sodium sulfate was 1%, the viscosity of the slurry reached up to 11.3 Pa.s, at which time the temperature rose to 37 • C. Contrary to sodium sulfate, single doping of lithium carbonate can significantly extend the duration of thickening period of liquid B.…”

Section: Effect Of Early Strength Agent On Sacdl Strengthmentioning

confidence: 99%

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

Chen,

Wang,

Jiao

et al. 2023

Materials

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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.

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Section: Effect Of Early Strength Agent On Sacdl Strengthmentioning

confidence: 99%