As the relative performance of alkali activated slag (AAS) concretes in comparison to portland cement (PC) counterparts for chloride transport and resulting corrosion of steel bars is not clear, an investigation was carried out and the results are reported in this paper. The effect of alkali concentration and modulus of sodium silicate solution used in AAS was studied. Chloride transport and corrosion properties were assessed with the help of electrical resistivity, non-steady state chloride diffusivity, onset of corrosion, rate of corrosion and pore solution chemistry. It was found that: (i) although chloride content at surface was higher for the AAS concretes, they had lower chloride diffusivity than PC concrete; (ii) pore structure, ionic exchange and interaction effect of hydrates strongly influenced the chloride transport in the AAS concretes; (iii) steel corrosion resistance of the AAS concretes was comparable to that of PC concrete under intermittent chloride ponding regime, with the exception of 6 % Na 2 O and Ms of 1.5; (iv) the corrosion behaviour of the AAS concretes was significantly influenced by ionic exchange, carbonation and sulphide concentration; (v) the increase of alkali concentration of the activator generally increased the resistance of AAS concretes to chloride transport and reduced its resulting corrosion, and a value of 1.5 was found to be an optimum modulus for the activator for improving the chloride transport and the corrosion resistance.

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This study reports an experimental investigation designed to assess the influence of near-surface moisture contents on permeation properties of alkali-activated slag concrete (AASC). Five different drying periods (5, 10, 15, 20 and 25 days) and three AASC and normal concretes with compressive strength grades ranging from C30 to C60 were considered. Assessment of moisture distribution was achieved using 100 mm diameter cores with drilled cavities. Results indicate that air permeability of AASC is very sensitive to the moisture content and its spatial distribution, especially at relative humidity above 65%. To control the influence of moisture on permeation testing, the recommendation of this paper is that AASC specimens should be dried in controlled conditions at 40 o C for 10 days prior to testing. It was also concluded from this study that AASC tends to perform less well, in terms of air permeability and sorptivity, than normal concrete for a given strength grade. This conclusion reinforces the need to further examine AASC properties prior to its widespread practical use.

11Ground granulated blast furnace slag (GGBS) is the most common industrial by-product used as a 12 precursor for alkali activated binders due to its fast setting, simple curing needs, and good early age 13 strength gain. There are conflicting findings on the chloride penetration resistance of such binders and 14 more information is required regarding the suitability of this type of binder material for chloride 15 environments. This article outlines the findings of investigation of alkali activated slag concretes 16 (AASC), to provide a comprehensive view of the effect of mix design variables on slump, strength, and 17 chloride transport and binding. It is concluded that AASC can be designed for different workability and 18 different grades of concrete. The diffusivity results demonstrate that the addition of excess water does 19 not directly control the pore structure/connectivity in AASC as it does for Portland cement, and 20 therefore AASC can be designed based on the water/binder ratio needed for a specified mechanical 21 performance. The chloride binding capacity increased as the paste content of the concrete and/or the 22 silica content of the activator was increased. 23 Keywords: alkali activated slag concretes (AASC); workability; strength; chloride diffusion and 24 chloride binding capacity 25

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