Dissolution and early hydration of tricalcium aluminate in aqueous sulfate solutions

Ye, Shaoxiong; Pan, Feng; Liu, Yao; Liu, Jiaping; Bullard, Jeffrey W.

doi:10.1016/j.cemconres.2020.106191

Cited by 27 publications

(9 citation statements)

References 40 publications

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“…This indicates an early onset of the alite hydration and an early formation of CH and C–S–H, respectively, which correlates well with the shift of the heat flow maximum to earlier times with increasing Ca(NO 3 ) 2 additions observed in isothermal calorimetry. The rate of C 3 A dissolution appears not to be affected by the presence of Ca(NO 3 ) 2 in solution during the first 6–8 h of hydration, which is in‐line with the results of Ye et al 59 . The initially observed gypsum reflex intensities in samples CN_2 and CN_5 are increased compared to sample CN_0.…”

Section: Resultssupporting

confidence: 90%

Working mechanism of calcium nitrate as an accelerator for Portland cement hydration

2022

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Precast concrete, cold weather concreting, and the emerging technique of concrete additive manufacturing are applications in which the acceleration of cement hydration plays a critical role. To allow precise control of early cement hydration in these applications, a thorough understanding of the working mechanisms of cement hydration accelerators is required. This study contributes to the understanding of the mechanism by which calcium nitrate (Ca(NO3)2) influences early cement hydration. The influence of Ca(NO3)2 on the hydration of an ordinary Portland cement has been followed by isothermal calorimetry, in situ X‐ray diffraction (XRD), quantitative XRD, compressive strength testing, and the analysis of the pore solution composition. Further, the initial pore solution, the initial phase composition, and the phase composition in the fully hydrated cement have been estimated by thermodynamic calculations to corroborate the experimentally obtained results. The results indicate that Ca(NO3)2, especially at the highest analyzed dosage of 5 wt.%, enhances the formation of ettringite and a nitrate‐containing AFm phase. Furthermore, Ca(NO3)2 accelerates alite hydration. Besides the increased Ca concentration in solution, it has been found that a reduction of the Al concentration in the initial pore solution by Ca(NO3)2 possibly contributes to the accelerating effect of Ca(NO3)2 on alite hydration.

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Section: Resultssupporting

confidence: 90%

Working mechanism of calcium nitrate as an accelerator for Portland cement hydration

2022

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“…In addition, the alkaline of the sulfate seems to play an important role in the retardation of C 3 A hydration. As observed by Ye et al [38], there is a cation-specific effect of sulfates on the delay of C 3 A hydration. While most studies agree that calcium sulfate retards the C 3 A hydration, there are contradictory results regarding the effect of other sulfate salts.…”

Section: Effect Of Calcium Sulfate On C 3 a Hydrationsupporting

confidence: 52%

“…While most studies agree that calcium sulfate retards the C 3 A hydration, there are contradictory results regarding the effect of other sulfate salts. Some authors have observed that magnesium sulfate retards the C 3 A hydration [27,37,38], while others have noted an increase in C 3 A hydration rate when adding magnesium sulfate [39]. The addition of sodium sulfate (Na 2 SO 4 ) either does not result in a delay [29,40] or delays to a less extent compared to calcium sulfate [27,38].…”

Section: Effect Of Calcium Sulfate On C 3 a Hydrationmentioning

confidence: 99%

Effects of sulfates on the hydration of Portland cement – A review

Neto

Torre

Kirchheim

2021

Construction and Building Materials

120

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“…[19][20][21][22] The adsorption hypothesis suggested that the suppression of C 4 AF/C 3 A hydration was caused by the adsorption of SO 4 2− or CaSO 4 on the reactive sites and hindered further dissolution. 22 Ye et al 23 confirmed that sulfate inhibited the evolution of etch pits and the dissolution of C 3 A by in situ observation. Recent work reported that the formation of an Al-rich leached surface and the adsorption of the Ca 2+ -SO 4 2− ion complex on this leach surface could explain the critical C 3 A dissolution rate limiting effect.…”

Section: Introductionmentioning

confidence: 86%

Understanding the adsorption of calcium sulfate on tetracalcium aluminoferrite and tricalcium aluminate surfaces

2023

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Calcium sulfate (CaSO4), an essential retarder in cement, retards the hydration of tricalcium aluminate (C3A) and tetracalcium aluminoferrite (C4AF) phases. However, its retarding mechanism remains unclear. This paper focused on the adsorption of CaSO4f on C4AF and C3A surfaces based on isothermal calorimetry, the measurement of the ionic concentrations in a diluted system, and density functional theory to enhance the understanding of the retardation mechanism. The results showed that the retarding effect of CaSO4 on C4AF was stronger than that on C3A due to the slower CaSO4 consumption rate, lower driving force for CaSO4 adsorption, and surface coverage of Fe(OH)3 gel. The adsorption of CaSO4 hindered Ca dissolution more markedly on C4AF than C3A, which was pronounced on Fe‐free C4AF surfaces. The adsorption of CaSO4 weakened the affinity of water on C4AF and C3A surfaces, lowering the driving force for H2O adsorption. The adsorption of H2O and CaSO4 promoted the dissolution of Al on the [AlO6] octahedral surface of C4AF, which may be responsible for the maintenance of a higher Al concentration in the solution. Based on the above results, the adsorption of CaSO4 on initial C4AF and C3A hydration was explained.

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Dissolution and early hydration of tricalcium aluminate in aqueous sulfate solutions

Cited by 27 publications

References 40 publications

Working mechanism of calcium nitrate as an accelerator for Portland cement hydration

Working mechanism of calcium nitrate as an accelerator for Portland cement hydration

Effects of sulfates on the hydration of Portland cement – A review

Understanding the adsorption of calcium sulfate on tetracalcium aluminoferrite and tricalcium aluminate surfaces

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