Properties and sustainability of alkali-activated slag foamed concrete

In the present study, 15 concrete mixes with dry density between 300 and 500 kg/m3 were tested for developing reliable mixing proportions, and establishing the significance of sustainable application of alkali-activated (AA) foamed concrete as a thermal insulation material in floor heating systems of buildings. Ground granulated blast-furnace slag (GGBS) was activated using the following three types of alkali activators: 10% Ca(OH)2 and 4% Mg(NO3)2, 5% Ca(OH)2 and 6.5% Na2SiO3, and 2.5% Ca(OH)2 and 6.5% Na2SiO3. The unit binder content varied in the concrete mixes corresponding to each type of activator. All mixes were produced using the pre-formed foam procedure with no aggregate or filler. The test results revealed that AA GGBS foamed concrete has considerable potential for practical applications when the unit binder content is close to 400 kg/m3, achieving the minimum quality requirements specified in the KS F 4039 as well as ensuring economic efficiency. Furthermore, the tested AA GGBS foamed concrete developed higher compressive strength than ordinary Portland cement (OPC) foamed concrete with the same dry density. In particular, a lifecycle assessment demonstrated a reduction in the environmental impact profiles of all specimens relative to typical OPC foamed concrete as follows: 99% for photochemical oxidation potential, 85-93% for global warming potential, 73-85% for abiotic depletion, and 68-85% for both acidification potential and human toxicity. Overall, the developed AA GGBS foamed concrete can be enlarged to sustainable varieties of cast-in-place structural fill and precast masonry materials.