Abstract: In response to the problem of long setting time and slow early strength development of sodium carbonate-activated ground blast furnace slag (GBFS) binders, the mechanical activation was adoptd to treat granulated blast furnace slag for accelerating the alkali-activation process. The effect of mechanical activation on the setting time, strength development, reaction kinetics and phase evolution of binders were investigated. The results show that mechanical activation can accelerate the dissolution and release of Ca²⁺, SiO₄ and AlO^-₄ in slag to promote the formation of calcium carboaluminate mineralogical phases. Accelerated dissolution of Ca²⁺ is beneficial for consuming CO^2-₃ in the liquid phase, and the initial and final setting time of binders decreases from 23.6 and 30.5 h to 2.3 and 3.2 h, respectively. At the same time, the induction period of alkali-activation is shortened using mechanical activation, the degree of alkali-activation is effectively improved, and the total heat release within 96 h increases from 41.30 J/g to 55.47 J/g. The formation of calcium aluminosilicate hydrate gel phase is promoted, which densifies the pore structure, reduces the total porosity from 30.49% to 27.01%, and reduces the macro-capillary porosity from 17.69% to 2.32%. The 28 d compressive strength of binders achieves 36.58 MPa, which increases to 230% compared with the reference sample.

Key words: alkali-activated slag, sodium carbonate, mechanical activation, setting time, compressive strength