Role of swelling agent and set-controlling admixtures on chloride binding and diffusion in cement matrix

Abstract

Chloride binding and diffusion was investigated for cement matrix with swelling agent (SA), early-strength agent (ESA) and set-retarding agent (SRA). Chloride binding isotherms (CBIs), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and thermodynamic modeling were applied to quantitatively reveal the mechanisms of chloride binding. The current results indicate that ESA will reduce chloride binding capacity and enhance chloride diffusivity due to the competition between sulphate and chloride. SRA holds a reverse regularity on account of increasing long-term hydration degree. The role of SA combines with kaolin and gypsum, resulting in a slighter reduction of chloride binding capacity.