Solidification of chloride ions in alkali-activated slag

Solidification effect reduces the content of free chloride ion in pore solution and moderates further penetration of chloride ion into concrete, thus reduces the risk of reinforcement corrosion. The influencing factors of the chloride solidification capacity of alkali-activated slag involving temperature, pH value and activator type are investigated experimentally in this work. The hydration products and micro-morphology of alkali-activated slag before and after immersion in chloride solution were analyzed comparatively. The physical adsorption and chemical binding of chloride by alkali-activated slag were quantitatively evaluated. The results show that the chloride binding amount of alkali-activated slag increases with temperature increasing but decreases with the pH value increasing. The binding capacity of slag activated by water glass is greater than that of slag activated by NaOH. The solidification of chloride of alkali-activated slag not only includes physical adsorption, but also a small amount of chemical binding. For all three pastes involving NaOH-activated slag, water glass-activated slag and portland cement, the physical adsorption in the solidification of chloride accounts for more than 50 %.