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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.

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

Graphene oxide/cement composite was prepared using a graphene oxide aqueous solution. The workability and mechanical properties of graphene oxide/cement composite with different concentrations for graphene oxide and the ratio of water to cement were investigated. The results observed were the fluidity of cement pastes decreased noticeably with the addition of graphene oxide and increased with the increase in the ratio of water to cement for all tested samples of different graphene oxide contents. It is indicated that a noticeable inverse correlation between the concentration of graphene oxide and fluidity was observed, and a positive linear relationship between the ratio of water to cement and fluidity was also obtained. The compressive strength of cement pastes significantly improved in the presence of an appropriate concentration of graphene oxide as compared to that of the cement paste without graphene oxide; this difference was due to the denser microstructure of graphene oxide/cement composite than that of the control specimens. With the combined analysis of X-ray diffraction and scanning electron microscopy with energy-dispersive spectrometry, the results showed that graphene oxide could promote and regulate the formation and connection of calcium hydroxide and calcium silicate hydrate during the hydration reaction, forming numerous regular and extremely compact plate-shaped crystals, and the compact plate-shaped microstructures constituted of not only calcium hydroxide and calcium silicate hydrate but also wrapped ettringite. This investigation will provide a flexible way to preparation of graphene oxide/cement composite with wanted fluidity and optimized compressive strength that promote the industry application of graphene oxide/cement composite.