Chloride diffusion of alkali-activated fly ash/slag concrete

Abstract

The widespread application of alkali-activated fly ash/slag (AAFS) concrete requires satisfaction of a series of performance criteria both from its early age properties (e.g. workability, strength) and long-term stability. In this study, long-term (till 180 days) natural chloride diffusion tests were conducted to evaluate the chloride diffusion in AAFS concretes prepared with different slag content, water-binder (w/b) ratio, alkali content, and sandaggregate ratio. The results revealed that the free chloride diffusion coefficient (Df) of AAFS concretes was between 0.4-1.8×10-12 m2/s. The slag content and w/b were found as dominant parameters affecting the long-term chloride transport in AAFS concretes, while the sandaggregate ratio presented a limited effect. MIP results indicated that capillary pores in AAFS reached percolation and became disconnected after 180 days. The long-term chloride diffusivity of AAFS concretes was closely related to the threshold pore diameter and volume of pores > 5 nm. The more larger pores, the higher chloride diffusion coefficient was