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BULLETIN OF THE CHINESE CERAMIC SOCIETY ›› 2026, Vol. 45 ›› Issue (1): 177-190.DOI: 10.16552/j.cnki.issn1001-1625.2025.0670

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Effect of Fluorine-Containing Composite Activator on Hydration Products and Properties of Steel Slag-Based Thermal Storage Cement

ZHOU Yelai(), MA Huibo, ZHANG Shidong, ZHAO Xianglin, ZHU Chun, KONG Haitao, LI Baorang()   

  1. School of Energy Power and Mechanical Engineering,North China Electric Power University,Beijing 102206,China
  • Received:2025-07-09 Revised:2025-08-15 Online:2026-01-20 Published:2026-02-10

Abstract:

In this study, a fluoride-containing composite activator (Na2SiO3·9H2O/Na2SO4/K2SO4/KF) was designed for steel slag (SS)-based thermal storage cement and applied to three cementitious systems: SS-Portland cement (PC), SS-calcium aluminate cement (CAC), and SS-calcium sulphoaluminate cement (CSA). The effect of activator dosage on compressive strength, thermal conductivity, and specific heat capacity was systematically evaluated, and the underlying activation mechanisms were investigated using XRD, TG-DTG, and SEM analyses. The results demonstrate that the alkaline environment generated by the activator effectively promotes the depolymerization of mineral phases in the steel slag-cement system, whereas the incorporation of F- suppresses the formation of ettringite (AFt) and calcium aluminate hydrates. Under the combined action of the activator, the depolymerized [Al(OH)4- and [H2SiO42- tend to form aluminum-rich calcium silicoaluminate hydrate (C-A-S-H) gel. The excess [Al(OH)4- is eventually converted into Al(OH)3. The formation of denser hydration products significantly enhances the mechanical and thermophysical properties of the paste, enabling all three systems to achieve or surpass the performance of pure cement paste. Among them, SS-PC and SS-CAC systems exhibit optimal overall performance at a 3% (mass fraction) activator dosage. However, excessive activator leads to reactions between Al(OH)3 and F-, hindering the strength development of the SS-CAC system. This study not only elucidates the mechanism of the fluoride-containing composite activator in SS-based thermal storage cement, but also provides a reference for the resource utilization of SS and the design of high-performance thermal storage cement.

Key words: concrete, steel slag, composite cementitious material, composite activator, hydration, sensible heat storage

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