Compressive strength, pore structure and chloride transport properties of alkali-activated slag/fly ash mortars

The effects of silicate modulus, alkali dosage, fly ash content and steam curing on compressive strength, pore structure and chloride transport properties of alkali-activated slag/fly ash (AASF) mortars have been investigated. The results showed that steam curing exhibited little influences on compressive strength and chloride transport properties of AASF mortars. The compressive strengths of AASF mortars increased with the increase of silicate modulus, alkali dosage, and decreased with the increase of the fly ash content due to the changes of pore structure within the range of 10-10(4) nm. The decrease of both chloride migration coefficient from the rapid chloride migration (RCM) test and passed charge from the rapid chloride permeability (RCP) test of AASF mortars were observed with the increase of silicate modulus and decrease of fly ash content due to the improvement of their pore structure in the aforementioned range. However, inconsistent results between RCM and RCP tests were observed with the increase of alkali dosage. The immersion of the AASF mortars in water decreased their passed charge due to the ion leaching out from their pore solution. The increase of water-to-specimen ratio increased the amount of leached substance and decreased the passed charge, but showed no effect on their chloride migration coefficient. Thus, RCM test is more suitable for characterization of chloride transport properties of alkali-activated materials than RCP test.