Chloride diffusion in alkali activated concrete

The corrosion resistance of steel reinforcement embedded in an alkali activated cementitious material (AACM) developed by Sheffield Hallam University (SHU) is being investigated. Two main initiators of corrosion, chloride diffusion and carbonation are being considered. This paper will present the results of chloride diffusion in the AACM concrete compositions under long term exposure (up to 180 days) by immersion in a 5% sodium chloride solution. Different mix compositions of the AACM concrete (four grades of mixes) suitable for structural application have been selected, representing different concentrations of the alkali activator and different binder and aggregate ratios. Parallel investigations on control samples of normal concrete of similar strength have been conducted. The chloride diffusion profiles with depth have been obtained. The results show a good correlation of chloride diffusion with Fick's second law of diffusion. A general reduction of chloride ion content within the AACM concrete matrix was observed compared to the control samples of normal concrete. Low liquid/binder ratio has a positive impact on strength, shrinkage and chloride diffusion of AACM concrete.