Resistance of alkali activated slag concretes to chloride environments

Researchers are focusing their attention on alternative binder systems with low environmental footprint. One such systems being considered is alkali activated slag concretes (AASC), made by adding alkalis such as sodium... [ view full abstract ]

Researchers are focusing their attention on alternative binder systems with low environmental footprint. One such systems being considered is alkali activated slag concretes (AASC), made by adding alkalis such as sodium hydroxide and sodium silicate to industrial by-products such as ground granulated blast furnace slag (GGBS). Whilst they have the similar behaviour as that of traditional cement systems in terms of strength and structural behaviour, AASC do exhibit superior performance in terms of abrasion and acid resistance, fire protection, etc.
In this article, the authors focus their attention on chloride ingress into different grades of AASC. The mix variables in AASC included water-to-binder, binder to aggregate ratio, percentage of alkali and the SiO2/Na2O ratio (silica modulus, Ms). The first challenge is to get mixes for different range of workability (with slump values from 40mm to 240mm) and reasonable early age and long term compressive strength according to each one. Then the chloride migration in those mixes were measured and compared with same normal concretes in the existed literature. Comparing the chloride ingress between tradition concretes and AASCs is worthwhile to prove the possibility of increasing concrete lifetime in proximity to sea and deciding if such concretes are practical for use. Compared to the PC concrete, the AAS concretes were found to have lower chloride migration.