The effects of polyaluminum chloride on the mechanical and microstructural properties of alkali-activated slag cement paste

In this study, an experimental investigation of the mechanical properties of alkali-activated slag cement (AASC) mixed with polyaluminum chloride (PAC) was conducted. The alkali activators were 5% sodium hydroxide and 5% sodium silicate of binder weight. The PAC substitution rate was varied by adjusting the mixing water weight from 0% to 10%, and the obtained samples were characterized by test for compressive strength, X-ray diffractometry, scanning electron microscopy (SEM), mercury intrusion porosimetry, thermogravimetric analysis, differential thermal analysis, and energy-dispersive X-ray spectroscopy. PAC substitution formed a dense C-A-S-H gel and Friedel's salt. SEM observations revealed that a dense matrix of hydration products and Friedel's salt existed in the pores. Moreover, greater amounts of PAC result in better mechanical performance. Thus, these hydration products enhance the strength of AASC by compacting the matrix and filling the voids.