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

Neto, Jorge Arigony; Torre, Ángeles G. De la; Kirchheim, Ana Paula

doi:10.1016/j.conbuildmat.2021.122428

Cited by 129 publications

(57 citation statements)

References 150 publications

(361 reference statements)

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“…Generally, three stable hydrate phases of calcium sulfate can be observed—(i) gypsum (CaSO 4 ·2H 2 O), (ii) α‐hemihydrate (α‐CaSO 4 ·0.5H 2 O), and (iii) anhydrite (CaSO 4 ) 92 . Numerous studies have been conducted to evaluate the effect of sulfate type and amount on CSA cement, PC, and CAC cement as an individual or binary systems 45,89,93–110 . Typically, 2%–10% gypsum is added to PC clinker to control setting, and 16%–25% gypsum is added to CSA cement to control setting time, volume stability, and mechanical strength improvement 106,111 .…”

Section: Binder Compositionmentioning

confidence: 99%

A critical review of the role of ettringite in binders composed of CAC–PC–C$ and CSA–PC–C$

2023

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Ettringite-accelerated binders composed of CAC-PC-C$ (calcium aluminate cement-Portland cement-calcium sulfate) and CSA-PC-C$ (calcium sulfoaluminate cement-Portland cement-calcium sulfate) have been used widely for indoor applications, such as self-leveling floor screeds, underlayment, and tile adhesives owing to their rapid setting, early strength gain, and shrinkage compensation properties. These properties also make these binders appealing candidates for outdoor rapid repair (e.g., highways, bridge decks, and airfield pavements). However, a central question remains: Does ettringite remain stable in outdoor exposure conditions? If so, which factors will contribute positively/negatively to the long-term stability of ettringite in these systems? To address these questions, this critical review presents the current state of knowledge regarding the hydration of ternary binders composed of CAC-PC-C$ and CSA-PC-C$ with respect to ettringite formation and the factors affecting the stability of ettringite thereafter. The purpose of this review paper is to synthesize and analyze current research regarding conditions that promote or deter ettringite stability, establish what information is missing, unclear, or contradictory, and identify remaining research needs to address the identified knowledge gaps.

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Section: Binder Compositionmentioning

confidence: 99%

A critical review of the role of ettringite in binders composed of CAC–PC–C$ and CSA–PC–C$

2023

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“…strength is difficult to determine, and it may cause corrosion damage to concrete products due to alkali-aggregate reaction or excessive sulfate [15]. The C-S-H crystal nucleation early strength agent (CNA) as a nucleation-type early strength agent can provide nucleation sites for hydration products of the initial stage of cement hydration, accelerate the generation of hydration products and promote the early hydration of cement [16][17][18].…”

Section: Synthesis Of Cnamentioning

confidence: 99%

“…For example, chlorine-based early-strength agents can cause corrosion of steel bars in concrete [13]. Triethanolamine (TEA) can significantly increase the early strength of cement-based materials, but cause a decrease in the flexural strength and late strength of cement [14], The mixing amount of traditional concrete early-strength is difficult to determine, and it may cause corrosion damage to concrete products due to alkali-aggregate reaction or excessive sulfate [15]. The C-S-H crystal nucleation early strength agent (CNA) as a nucleation-type early strength agent can provide nucleation sites for hydration products of the initial stage of cement hydration, accelerate the generation of hydration products and promote the early hydration of cement [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Effect of C-S-H Nucleating Agent on Cement Hydration

Zhao

Ji²,

Jiang

et al. 2021

Applied Sciences

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This work aims to study the effect of a nucleating agent on cement hydration. Firstly, the C-S-H crystal nucleation early strength agent (CNA) is prepared. Then, the effects of CNA on cement hydration mechanism, early strength enhancement effect, C-S-H content, 28-days hydration degree and 28-days fractal dimension of hydration products are studied by hydration kinetics calculation, resistivity test, BET specific surface area test and quantitative analysis of backscattered electron (BSE) images, respectively. The results show that CNA significantly improves the hydration degree of cement mixture, which is better than triethanolamine (TEA). CNA shortens the beginning time of the induction period by 49.3 min and the end time of the cement hydration acceleration period by 105.1 min than the blank sample. CNA increases the fractal dimension of hydration products, while TEA decreases the fractal dimension. CNA significantly improves the early strength of cement mortars; the 1-day and 3-days strength of cement mortars with CNA are more than the 3-days and 7-days strength of the blank sample. These results will provide a reference for the practical application of the C-S-H nucleating agent.

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“…The kinetic of hydration of the ye'elimite phase is very fast and almost independent of the amount of anhydrite or water-to-cement ratio [18] but it can be influenced by the presence of other aluminates [19]. In addition, the sulphate content and type affect the kinetic of silicates in general [20,21], and belite in particular [18,22], by retarding their hydration with the increase in sulphate dissolution. The decrease of water-to-cement (w/c) ratio is a positive strategy to enhance mechanical strengths [23,24] but its effect on hydration kinetics is still not fully understood, especially the effect on phase assemblage and microstructural development [25].…”

Section: Introductionmentioning

confidence: 99%

Effect of Boron and Water-to-Cement Ratio on the Performances of Laboratory Prepared Belite-Ye’elimite-Ferrite (BYF) Cements

et al. 2021

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The effect of superplasticiser, borax and the water-to-cement ratio on BYF hydration and mechanical strengths has been studied. Two laboratory-scale BYF cements—st-BYF (with β-C2S and orthorhombic C4A3S¯) and borax-activated B-BYF (with α’H-C2S and pseudo-cubic C4A3S¯)—have been used, and both show similar particle size distribution. The addition of superplasticiser and externally added borax to BYF pastes has been optimised through rheological measurements. Optimised superplasticiser contents (0.3, 0.4 and 0.1 wt % for st-BYF, B-BYF and st-BYF with externally added 0.25 wt % B2O3, respectively) result in low viscosities yielding homogeneous mortars. The calorimetric study revealed that st-BYF is more reactive than B-BYF, as the values of heat released are 300–370 J/g and 190–210 J/g, respectively, after 7 days of hydration; this fact is independent of the water-to-cement ratio. These findings agree with the higher degree of hydration at 28 days of β-C2S in st-BYF (from 45 to 60%) than α’H-C2S in B-BYF (~20 to 30%). The phase assemblage evolution has been determined by LXRPD coupled with the Rietveld method and MAS-NMR. The formation of stratlingite is favoured by increasing the w/c ratio in both systems. Finally, the optimisation of fresh BYF pastes jointly with the reduction of water-to-cement ratio to 0.40 have allowed the achieving of mortars with compressive strengths over 40 MPa at 7 days in all systems. Moreover, the st-BYF mortar, where borax was externally added, achieved more than 70 MPa after 28 days. The main conclusion of this work does not support Lafarge’s approach of adding boron/borax to the raw meal of BYF cements. This procedure stabilises the alpha belite polymorph, but its reactivity, in these systems, is lower and the associated mechanical strengths poorer.

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

Cited by 129 publications

References 150 publications

A critical review of the role of ettringite in binders composed of CAC–PC–C$ and CSA–PC–C$

A critical review of the role of ettringite in binders composed of CAC–PC–C$ and CSA–PC–C$

Effect of C-S-H Nucleating Agent on Cement Hydration

Effect of Boron and Water-to-Cement Ratio on the Performances of Laboratory Prepared Belite-Ye’elimite-Ferrite (BYF) Cements

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