Effect of curing temperature on the reaction kinetics of cementitious steel slag-fly ash-desulfurized gypsum composites system

Solid waste-based binders have been widely studied for decades. Recently, the steel slag-fly ash-desulfurized gypsum (SS-FA-DG) composite system was developed as a novel building cementi-tious material, however, its reaction mechanism and reaction process mains unclear. This paper investigated the reaction kinetics of SS-FA-DG composite system by evaluating the influence of curing temperature on the formation of hydration products and the development of mechanical properties. The pH of the SS-FA-DG slurry was measured by the online pH meter. The compres-sive strength, chemical bonding, mineral composition, and degree of hydration of cementitious SS-FA-DG blocks over a curing period of 28 days were evaluated using compression tests, Fourier transform infrared spectroscopy, X-ray diffraction and thermogravimetric analyses, respectively. The results indicate that the SS-FA-DG composite system was found to develop via a five-stage process: dissolution of steel slag (I) and fly ash (II), formation of hydration products such as cal-cium silicate hydrate gels (C-S-H) and ettringite (AFt) crystallite (III), nucleation and crystalliza-tion of hydration products (IV), and growth and diffusion (V). The compressive strength was largely governed by the development of the hydration reaction, which is influenced by the curing temperature. The reaction time of each stage was shortened at elevated curing temperatures, thereby increasing the compressive strength of the material more quickly.

Automated summary

This paper investigated the reaction kinetics of the steel slag-fly ash-desulfurized gypsum (SS-FA-DG) composite system by evaluating the influence of curing temperature on the formation of hydration products and the development of mechanical properties. The results indicated that the SS-FA-DG composite system developed through a five-stage process, and the compressive strength was largely influenced by the development of the hydration reaction and the curing temperature.