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<p>Natural gypsum (NG) is commonly used as a retarder in the production of AAC production to regulate slurry thickening. The calcium oxide–belite–calcium sulphoaluminate (CBCSA) system has been developed to replace OPC and quicklime for AAC manufacturing, yet the mechanistic role of NG in governing the early hydration behavior of CBCSA remains underexplored. This study systematically investigates the influence of NG dosage on the phase evolution, hydration kinetics, and microstructural development of CBCSA. QXRD and TGA were used for quantitative phase evolution characterisation. Isothermal calorimetry coupled with the Kondo model was used to quantify the retardation effect of NG on the hydration kinetics of CBCSA. <sup>1</sup>H NMR was used to track the pore structure evolution. SEM–EDS was used to analyse the morphology and composition of hydration products. Results show that NG exhibits a time-dependent regulatory effect on the mineral phases of CBCSA: it notably retards the hydration of CaO within 4&#xa0;h, inhibits the hydration of C<sub>4</sub>A<sub>3</sub>$ over 72&#xa0;h, and shows dual effects on the hydration of C<sub>2</sub>S. In terms of hydration heat evolution, NG reduces the first exothermic peak intensity, introduces an induction stage and delays the second exothermic peak, thereby modulating the hydration control mechanism. Moreover, while NG increases capillary porosity at early stages, it ultimately contributes to a denser microstructure in later stages by promoting&#xa0;C<sub>2</sub>S&#xa0;hydration. These findings contribute to a theoretical framework that supports the practical application of CBCSA in AAC production.</p>

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Influence of natural gypsum on the early hydration and pore structure of the calcium oxide–belite–calcium sulphoaluminate cementitious materials

  • 期刊论文

  • 发表日期：

    2026年4月22日

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  • Yanqing Xia,
  • Zhenyu Lai,
  • Ning Wang,
  • Xuemei Chen,
  • Yangyang Kang,
  • Xirui Lu

摘要

Natural gypsum (NG) is commonly used as a retarder in the production of AAC production to regulate slurry thickening. The calcium oxide–belite–calcium sulphoaluminate (CBCSA) system has been developed to replace OPC and quicklime for AAC manufacturing, yet the mechanistic role of NG in governing the early hydration behavior of CBCSA remains underexplored. This study systematically investigates the influence of NG dosage on the phase evolution, hydration kinetics, and microstructural development of CBCSA. QXRD and TGA were used for quantitative phase evolution characterisation. Isothermal calorimetry coupled with the Kondo model was used to quantify the retardation effect of NG on the hydration kinetics of CBCSA. 1H NMR was used to track the pore structure evolution. SEM–EDS was used to analyse the morphology and composition of hydration products. Results show that NG exhibits a time-dependent regulatory effect on the mineral phases of CBCSA: it notably retards the hydration of CaO within 4 h, inhibits the hydration of C4A3$ over 72 h, and shows dual effects on the hydration of C2S. In terms of hydration heat evolution, NG reduces the first exothermic peak intensity, introduces an induction stage and delays the second exothermic peak, thereby modulating the hydration control mechanism. Moreover, while NG increases capillary porosity at early stages, it ultimately contributes to a denser microstructure in later stages by promoting C2S hydration. These findings contribute to a theoretical framework that supports the practical application of CBCSA in AAC production.