The paper investigates the effect of wet/dry, wet and dry curing on the pore properties and strength of an alkali activated cementitious (AACM) mortar. The pore characteristics were determined from the cumulative and differential pore volume curves obtained by mercury intrusion porosimetry. AACM mortars possess a bimodal pore size distribution while the control PC mortar is unimodal. AACM mortars have a lower porosity, higher capillary pore volume, lower gel pore volume and lower critical and threshold pore diameters than the PC mortar which indicate greater durability potential of AACMs. Wet/dry curing is optimum for AACM mortars while wet curing is optimum for the PC mortar. Shrinkage and retarding admixtures improve the strength and pore structure of the AACMs.

This work was carried out in collaboration between all authors. Author OYO designed the study, performed the statistical analysis, wrote the protocol, and wrote the first draft of the manuscript and managed literature searches. Authors AAA, SBR and SJA managed the analyses of the study and literature searches. All authors read and approved the final manuscript.

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The use of ordinary Portland cement (PC) as the principal binder in concrete brings with it significant environmental challenges through the consumption of fossil fuels and emission of carbon dioxide (CO 2 ) during cement production. Concrete specimens made with an alkali activated cementitious material (AACM) produced from an alternative binder and conventional Portland cement concrete were exposed to corrosion inducing environments for 1 750 days to monitor their relative durability. AACM concrete shows higher corrosion potential E corr and corrosion current densities I corr than PC concrete due to a reducing environment around the steel surface in AACM concrete, caused by high sulfide concentration in the pore solution.Corrosion resistance of the AACM concretes increases with increasing molarity of the alkali activator, at a constant liquid to binder ratio. The threshold Cl -/OHvalue for pitting corrosion initiation in the AACM concrete is between 2.1 and 2.8 compared with 1.08 for the control PC concrete. The AACM concrete evaluated in this study showed greater resistance to chloride induced corrosion than the PC concrete.

This paper investigates the free chloride profiles, diffusion parameters and chloride binding capacity of an alkali activated concrete (AACM) together with a control Portland cement (PC) concrete. Ggbs based AACM concrete specimens with different molarity of activator were exposed to a 5% NaCl solution for 540days to determine their free chloride diffusion properties. The relationships between the free and bound chloride concentration were determined by applying Freundlich and Langmuir isotherms. The required cover to steel reinforcement for corrosion prevention is derived to satisfy the limiting thresholds of free and bound chloride concentrations.The results show that Fick's second law of diffusion applies to the free chloride profiles of AACM concrete and provides higher values of diffusion coefficients than a similar grade of PC concrete. The relationship between the free and bound chlorides is defined by the Langmuir isotherm. PC concrete has higher chloride binding capacity than AACM concrete for both water and acid soluble chlorides. Less concrete cover to steel reinforcement is required in AACM than PC concrete when calculated by using the bound chloride concentration threshold limit. The values of cover based on the corresponding free chloride limit in AACM concrete are higher than its bound chloride values. Ca 6 Fe 2 O 6 .CaCl 2 .10H O kuzel's salt (KS) ISE ion selective electrode D ref diffusion coefficient at reference time t t ref reference age (days) m age factor C ref surface chloride concentration corresponding to the time k constant for surface chloride concentration C-S-H calcium silicate hydrate CH portlandite AFm monosulfoaluminate AFt ettringite C-S-H calcium silicate hydrate N-A-S-H sodium aluminosilicate hydrate SCMs supplementary cementitious materials