Investigation of Hydration Temperature of Alkali Activated Slag Based Concrete

Abstract

This paper presents the results of an investigation on the effect of activator type, binder amount and sodium dosage on hydration heats of Alkali-Activated Slag (AAS) concrete. For the slag activation, sodium hydroxide (NaOH) pellets and the mixture of NaOH+liquid sodium silicate (Na2SiO3) were used at three sodium concentrations, 4%, 6% and 8% by mass of slag. Twenty one different mixtures were prepared for the laboratory tests. In the reference three mixtures, OPC was used as binder and in the other AAS mixtures Granulated Blast Furnace Slag (GBFS) was used. The binder dosages were 300, 350 and 400 kg/m3 and the waterbinder (w/b) ratio used in the mixtures was 0.50. The compressive strength and hydration temperature of produced concretes were measured. The temperature change of specimens measured in every 15 minutes until 120 hours. The test results showed that, the compressive strengths and hydration temperatures of the mixtures increased depending on increasing binder amount and sodium dosage. The use of NaOH+Na2SiO3 mixture as activator increased compressive strength but decreased hydration temperature of the mixtures. The hydration temperatures of all AAS mixtures were lower than OPC mixtures. Produced AAS concrete with low hydration temperature can be an alternative in recycled construction material at mass concrete applications.