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Hydration characterization of Mg2+ blended excess-sulphate phosphogypsum slag cement system during early age
Highlights Incorporation of magnesium ions leads to a remarkable retarding effect of magnesium ions at the induction period, which is accompanied with a slow development of pH value, low availability, and accumulation rate of hydrated phases. Release of impurities is a continuous process spanning multiple stages, including induction and acceleration period of hydration. Magnesium ions slow down the precipitation of impurities and inhibit the dissolution of phosphogypsum, proved by a remarkable reduction in phosphorus and sulphur concentrations. On the other hand, magnesium ions would accelerate cement and slag hydration. Under the combined effects, the incorporation of magnesium within 0.2 mol/L would advance the acceleration period. Magnesium ions affect the precipitation efficiency of impurities due to the consumption of portlandite in the generation of brucite. Incorporation of magnesium poses a negative effect on early strength while positive at the late stage, especially for flexural strength of the PESSC pastes, implying that the preparation of PESSC pastes by seawater is preferable for the actual application.
Abstract Phosphogypsum-based excess-sulphate slag cement (PESSC) shows great resistance to sulphate and chloride ion erosion, and is expected to be an effective sink of waste phosphogypsum, to alleviate environmental pressure. Understanding the effect of magnesium ions is essential for the engineering application of PESSC in marine environment. In this paper, heat evolution, pore solution composition, phases assemblage, and mechanical properties of PESSC are characterized and analysed to reveal the effect of magnesium ions on early hydration and strength development. Results demonstrate that magnesium ions prolong the induction period and lead to a longer setting time. Increasing magnesium ions concentration from 0 mol/L to 0.2 mol/L makes the acceleration period appear earlier, and affects content of hydration products such as ettringite and C-(A)-S-H gel at early stage. Compressive and flexural strength can be significantly improved with magnesium ions addition at various degrees. It turns out that seawater could be favourable for PESSC if applied in marine environment.
Hydration characterization of Mg2+ blended excess-sulphate phosphogypsum slag cement system during early age
Highlights Incorporation of magnesium ions leads to a remarkable retarding effect of magnesium ions at the induction period, which is accompanied with a slow development of pH value, low availability, and accumulation rate of hydrated phases. Release of impurities is a continuous process spanning multiple stages, including induction and acceleration period of hydration. Magnesium ions slow down the precipitation of impurities and inhibit the dissolution of phosphogypsum, proved by a remarkable reduction in phosphorus and sulphur concentrations. On the other hand, magnesium ions would accelerate cement and slag hydration. Under the combined effects, the incorporation of magnesium within 0.2 mol/L would advance the acceleration period. Magnesium ions affect the precipitation efficiency of impurities due to the consumption of portlandite in the generation of brucite. Incorporation of magnesium poses a negative effect on early strength while positive at the late stage, especially for flexural strength of the PESSC pastes, implying that the preparation of PESSC pastes by seawater is preferable for the actual application.
Abstract Phosphogypsum-based excess-sulphate slag cement (PESSC) shows great resistance to sulphate and chloride ion erosion, and is expected to be an effective sink of waste phosphogypsum, to alleviate environmental pressure. Understanding the effect of magnesium ions is essential for the engineering application of PESSC in marine environment. In this paper, heat evolution, pore solution composition, phases assemblage, and mechanical properties of PESSC are characterized and analysed to reveal the effect of magnesium ions on early hydration and strength development. Results demonstrate that magnesium ions prolong the induction period and lead to a longer setting time. Increasing magnesium ions concentration from 0 mol/L to 0.2 mol/L makes the acceleration period appear earlier, and affects content of hydration products such as ettringite and C-(A)-S-H gel at early stage. Compressive and flexural strength can be significantly improved with magnesium ions addition at various degrees. It turns out that seawater could be favourable for PESSC if applied in marine environment.
Hydration characterization of Mg2+ blended excess-sulphate phosphogypsum slag cement system during early age
Wang, Ziyan (author) / Shui, Zhonghe (author) / Li, Zhiwei (author) / Sun, Tao (author) / Ye, Zhiyi (author)
2022-06-17
Article (Journal)
Electronic Resource
English
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