CARBONATION RESISTANCE OF SLAG MORTARS ACTIVATED BY DIFFERENT ALKALI ACTIVATORS

Abstract

In this study, the carbonation depths of slag mortars activated by sodium silicate (water glass), sodium hydroxide and sodium carbonate were investigated and the results were compared to those of control mortar with CEM I 42.5 R normal Portland cement. In the mixture, the sand/binder ratio was 2.75 and the water/binder ratio was 0.50. Na concentrations in the mixture proportions were determined as 4%, 6%, and 8% for all the activators. For liquid sodium silicate activator, SiO2/Na2O ratios (Ms) of 0.75, 1, 1.25, and 1.5 were also chosen. Prismatic specimens having 40 x 40 x 160 mm dimensions were prepared from both fresh Portland cement and slag mortar mixtures for the measurements. The day after the mortar casting, the prisms were demolded and placed in a humidity cabinet at 65% ± 5 relative humidity and 22 ± 2 °C temperature. The carbonation tests of mortars were conducted at 7, 28, 90 and 180 days. It was observed that the carbonation resistance of slag mortars activated by alkalis was lower than that of control mixture with Portland cement. However, it was also seen that an increment in the Na dosage of activator improved the resistance of the activated slag mortars to carbonation.