Effect of Temperature and pH on Early Hydration Rate and Apparent Activation Energy of Alkali-Activated Slag

Li, Ping; Tang, Jianhui; Chen, Xudong; Bai, Yanqin; Li, Qiyao

doi:10.1155/2019/3531543

Cited by 5 publications

(3 citation statements)

References 30 publications

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“…This further indicates that the measured system is far from a dissolution-controlled regime since it is known that the dissolution of a given material is highly dependent on the pH. This is supported by the work of Li et al, whose results indicate that the pH has a significant effect on the value of the E a for systems of alkali-activated slag in the range between pH 12 and pH 13.6, revealing an E a at 1 day in the range of 70–96 kJ/mol for a pH 12 and around 3 kJ/mol for a pH 13.6 [ 27 ].…”

Section: Discussionmentioning

confidence: 70%

The Apparent Activation Energy of a Novel Low-Calcium Silicate Hydraulic Binder

Antunes

Santos²,

Pereira³

et al. 2021

Materials

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In this work, the apparent activation energy (Ea) of a novel low-calcium binder was, for the first time, experimentally determined, using a calorimetric approach. Additionally, a correlation between the Ea, measured at the acceleration period with the C/S ratio of the hydration product is proposed. The Ea of the prepared pastes was determined through isothermal calorimetry tests by calculating the specific rate of reaction at different temperatures, using two different approaches. When comparing the Ea, at the acceleration period of this novel binder with the one published for alite and belite, we observed that its value is higher, which may be a result of a different hydration product formed with a distinct C/S ratio. Finally, to study the temperature effect on the compressive strength at early ages, a set of experiments with mortars was performed. The results showed that the longer the curing time at 35 °C, the higher the compressive strength after 2 days of hydration, which suggests a higher initial development of hydration products. This study also indicated that the novel binder has a higher sensitivity to temperature when compared with ordinary Portland cement (OPC).

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Section: Discussionmentioning

confidence: 70%

The Apparent Activation Energy of a Novel Low-Calcium Silicate Hydraulic Binder

Antunes

Santos²,

Pereira³

et al. 2021

Materials

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“…In addition, ∆H θ = and ∆S θ = also changed significantly when the H 2 O 2 concentration increased to 0.14 vol.%. Referring to the theoretical calculations and the experimental results in previous studies, E a is independent of reactant concentration, but is influenced by the change in reactants and the products of the oxidation reaction [39,[41][42][43][44]. It is therefore reasonable to infer according to the changes in E a that when the H 2 O 2 concentration is further increased to 0.14 vol.%, easier oxidation between chalcopyrite and H 2 O 2 can occur.…”

Section: Discussionmentioning

confidence: 91%

A Quantitative Relationship between Oxidation Index and Chalcopyrite Flotation Recovery

Yang

Chen

et al. 2022

Minerals

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The surface oxidation of chalcopyrite is one of the most important factors affecting its flotation performance. In this study, a critical oxidation degree is proposed to define “slight” and “significant” oxidation in terms of surface species and chalcopyrite flotation recovery. Slight oxidation enhanced chalcopyrite hydrophobicity, but significant oxidation reduced its recovery apparently. Microthermokinetic measurements indicated that the apparent activation energy (Ea) of chalcopyrite oxidation was reduced from around 173 kJ·mol−1 to 163 kJ·mol−1 when the reaction changed from slight oxidation to significant oxidation when applying H2O2. The surface oxidation degree was defined as the ratio of hydrophilic species to hydrophobic species. The highest recovery (94.8%) and contact angle (93°) were achieved at a concentration of 0.1 vol.% H2O2, with the lowest oxidation degree of 0.388 being observed. The oxidation degree was correlated to the flotation recovery, with a quantitative relationship (y = −298.81x + 213.05, y and x represent flotation recovery and oxidation degree, respectively, 0.388 ≤ x ≤ 0.618) being established, thereby giving a guideline to better manage chalcopyrite flotation by controlling its surface oxidation and SBX adsorption on chalcopyrite surfaces.

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“…Gu et al 16 and Du et al 17 reported that the early reaction rate of AAS at low temperature (5–7°C) was slow, but the compressive strength of mortar cured for 3 days at 7°C reached 18.4 MPa. Samantasinghar and Singh 18 and Li et al 19 also stated that when the slag was activated with NaOH, the reaction rate of slag at the early age at low temperature was slow, especially for low alkali (pH ≤ 13.02) dosage.…”

Section: Introductionmentioning

confidence: 99%

Using calcium‐rich precursors to improve the early‐compressive strength of alkali‐activated slag cement at low temperature

Yang

Deng

et al. 2021

Structural Concrete

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This study examines the potential of using calcium-rich precursors to improve the strength of alkali-activated slag (AAS) cement at low temperature. To achieve this target, the effect of calcium-rich precursors on the early strength development of AAS mortars cured at 5 C was assessed. The strength development was investigated along with its internal temperature, microstructure and reaction products. It is found that the calcium-rich precursors can improve the early strength of AAS around 35% and the group with Portland cement clinker gave the highest strength. Calcium oxide can also increase the compressive strength of AAS cement, but its effectiveness is not as good as the sample with clinker. Adding calcium sulfoaluminate can increase the early strength, while no significant contribution to 28-day strength could be found. The results highlight that compressive strength of modified AAS mortar can reach 15 MPa at 6 h and 20 MPa at 24 h at 5 C, suggesting that this binder could be a valuable alternative for low temperature construction.

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Effect of Temperature and pH on Early Hydration Rate and Apparent Activation Energy of Alkali-Activated Slag

Cited by 5 publications

References 30 publications

The Apparent Activation Energy of a Novel Low-Calcium Silicate Hydraulic Binder

The Apparent Activation Energy of a Novel Low-Calcium Silicate Hydraulic Binder

A Quantitative Relationship between Oxidation Index and Chalcopyrite Flotation Recovery

Using calcium‐rich precursors to improve the early‐compressive strength of alkali‐activated slag cement at low temperature

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