The influence of alkali metals on the mineral formation of sulphosilicate cement clinker

Sulphosilicate cement clinker (SSC) is a new type of low-carbon clinker system. Understanding the doping behavior of alkali metal ions is important for optimizing the quality and performance of cement clinker. However, the effect of alkali metal doping on SSC is still in a blank stage. This paper investigates the sintering behavior and microstructural evolution of alkali metal ions in SSC. By combining experiments and density functional theory simulations, the doping preference of alkali metal ions in SSC is revealed. The results showed that appropriate amounts of Li + (0.5%), Na + (1%) and K + (0.5%) can promote mineral formation and reduce the sintering temperature of SSC by 50–100 °C. However, excessive alkali metals can accelerate the decomposition of C 5 S 2 $. The mineral particles in clinker aggregate with each other to form agglomerates of varying sizes. Li + is solidly soluble in C 4 A 3 $, C 5 S 2 $ and C 2 S by substitution of Ca 2+ or interstitial filling, while Na + and K + are solidly soluble only by substitution of Ca 2+ . DFT simulations further confirm that C 2 S has the optimal Ca site substitution efficiency, while the crystal structure of C 4 A 3 $ is more likely to accommodate interstitial filling, especially Li + can spontaneously occupy the interstitial sites. The study elucidated the sintering behavior, existence form and doping mechanism of alkali metals, providing theoretical guidance for the preparation of SSC.