Feasibility of Sodium Hydroxide Treatment to Improve the Reactivity of Dolomite in Metakaolin‐Based Geopolymers

ABSTRACT Dolomite (DM) is an abundant mineral, but due to its low reactivity, it is mostly used as an inert filler in geopolymers (GPs). Existing activation methods cannot solve this problem in a low‐carbon and efficient way. A low‐carbon method, treating DM with sodium hydroxide solution, is proposed to improve the reactivity of DM. Alkali treatment effectively mitigates the retarding effect of raw DM, offsetting 69% of the total retarded time caused by the addition of 10 wt% raw DM, as evidenced by Vicat penetration and isothermal calorimetry. This acceleration is attributed to the promoted dissolution of metakaolin and increased precipitation of GP gels, as determined by chemical extraction. Furthermore, Fourier transform infrared spectroscopy analysis corroborates this structural evolution by revealing a reduced Si/Al ratio within the gel network. Mechanistically, the process is driven by DM dissolution, which yields Ca(OH) 2 , Mg(OH) 2 , and CaCO 3 precipitates, as confirmed by X‐ray diffractometer and thermogravimetric analysis‐differential scanning calorimetry analyses. Consequently, this strategy effectively enhances DM reactivity and promotes GP hardening.