Abstract
To provide basic data for the reasonable mixing design of the alkali-activated (AA) foamed concrete as a thermal insulation material for a floor heating system, 9 concrete mixes with a targeted dry density less than 400 kg/m3 were tested. Ground granulated blast-furnace slag (GGBS) as a source material was activated by the following two types of alkali activators: 10% Ca(OH)2 and 4% Mg(NO3)2, and 2.5% Ca(OH)2 and 6.5% Na2SiO3. The main test parameters were water-to-binder (W/B) ratio and the substitution level (RFA) of fly ash (FA) for GGBS. Test results revealed that the dry density of AA GGBS foamed concrete was independent of the W/B ratio an RFA, whereas the compressive strength increased with the decrease in W/B ratio and with the increase in RFA up to 15%, beyond which it decreased. With the increase in the W/B ratio, the amount of macro capillaries and artificial air pores increased, which resulted in the decrease of compressive strength. The magnitude of the environmental loads of the AA GGBS foamed concrete is independent of the W/B ratio and RFA. The largest reduction percentage was found in the photochemical oxidation potential, being more than 99%. The reduction percentage was 87% - 93% for the global warming potential, 81% - 84% for abiotic depletion, 79% - 84% for acidification potential, 77% - 85% for eutrophication potential, and 73% - 83% for human toxicity potential. Ultimately, this study proved that the developed AA GGBS foamed concrete has a considerable promise as a sustainable construction material for nonstructural element.
Highlights
Most of residential buildings and houses in Korea adopt a floor heating system
Test results revealed that the dry density of AA Ground granulated blast-furnace slag (GGBS) foamed concrete was independent of the W/B ratio an RFA, whereas the compressive strength increased with the decrease in W/B ratio and with the increase in RFA up to 15%, beyond which it decreased
The substitution of fly ash (FA) accelerates the burst of bubbles in AA GGBS foamed concrete
Summary
Most of residential buildings and houses in Korea adopt a floor heating system. The floor radiation heating system is commonly estimated to be lower as much as 50% in energy consumption compared with convection heating system [1]. The air-void system of foamed concrete, which significantly influences the strength and thermal conductivity of such concrete, depends on mixing proportions including water-to-binder ratio, foam volume and amount of filler as well as the performance of foam agent [12]. Another current concern for the foamed concrete is sustainable quality. The present experimental program was conducted as a follow-up to the previous investigation [10] to suggest a reasonable mixing proportion of AA GGBS foamed concrete for thermal insulation material in a floor heating system based on the various test data and understanding the behavior of such concrete. The environmental impacts of test mixes were compared with those calculated from a typical OPC foamed concrete mix
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