Engineering properties of self-compacting alkali-activated blast furnace slag mortars produced with lightweight pumice aggregate

Portland cement, which has been used as an unrivaled binder material since its development is responsible for 8% of CO2 emissions from human activities. Alkali-activated materials based on the principle of activating aluminosilicate-based materials by means of alkali activators are a binder developed for environmental gains in the construction industry. The production of mortars/concrete having different properties with alkali-activated materials may eliminate the concerns about the use of these materials in the construction industry. Firstly, the effects of Na2SiO3/NaOH ratio, Portland cement replacement ratio and curing temperature on the compressive strength were investigated with 34 series of paste mixes produced. 48 series of mortar mixtures were produced using pumice aggregate. Mixtures having best compressive strength and flow diameter were determined. The mixtures determined were reproduced for high temperature and sulfate attack tests. The high temperature resistance of the mortar specimens was investigated by compressive strength test, UPV measurement, scanning electron microscop, fourier-transform infrared spectroscopy and X-ray diffraction analysises. Sulfate resistance of the mixtures, on the other hand, was investigated by performing fourier transform infrared spectroscopy analysis as well as compressive strength test, weight change measurement and visual inspection of the specimens immersed in 5% concentrated Na2SO4 and MgSO4 solutions. In this study the alkali-activated mortar produced using light-weight aggregate reached a flow diameter of 240 mm. It was observed that there was no spalling occurred even in the specimens exposed to 1000 °C. There was an increase in the strength of the specimens after 1000 °C temperature exposure compared to 800 °C temperature exposure. In accordance with the changes in the visual appearance, the strength of the specimens immersed in MgSO4 solution decreased significantly at the end of six months, while the strength of the specimens immersed in Na2SO4 solution for the same period increased by values ranging from 21.4% to 37%. The sulfate resistance of the specimens, which consisted entirely of slag as binder, was higher than their Portland cement substituted counterparts, as was the high temperature resistance.