| Magnesium slag, which was a by-product from the in the production of magnesium industry, was usually considered as a typeindustrial wastes. However instead of appropriate treatment, it was usually land filled which can not only result in the occupation of land resources but also environmental pollution. On the other hand, magnesium slag was rich in C3 S, C2 S and C3 A, which show hydraulic potential, so it can be possibly used to produce wall materials, especially aerated concrete. In this thesis work, the propertiesincluding stability of slurry, dry density, strength, durability and thermal performance of aerated concrete based on magnesium slag were investigated. The hydration products and microstructure of the materials were characterized by XRD?FT-IR?DSC-TG and SEM.The main conclusions of this paper were given.The order of factors which affect the stability of slurry were: the content of the alkali?the dosage of the foam?the ratio of the water to the material?the modulus of the water glass.In terms of mix proportion of the slurry,magnesium slag: fly ash: metakaolin was 16:3:1(in mass).In the mixture, the modulus of water glass was 1.5, the alkali equivalent was 7wt%, the ratio of water to material was 0.32, the amount of aluminates powder was 4‰ and the amount of stable foam agentwas 0.5‰ showed the best effect. The best way to adjust the dry density of alkali activated magnesium slag aerated concrete. When aluminum powder dosage of 3 ‰, 4 ‰, 5 ‰, the base of magnesium slag aerated concrete dry density was415 kg/ m3,495 kg/ m3 and 589 kg/ m3.Results also showed that the most appropriatecuring process of alkali activated almagnesium slag aerated concrete were constant temperature and humidity curing process. When the relative humidity was 80%, constant temperature was 80 ?, holding time was 5 hours, the strength could meet the level of B04, B05, B06 which were stated in GB11968-2006. The 60 d dry shirking of alkali activated almagnesium slag aerated concrete with dry density level were B05, B06 were 0.421mm/m,0.486mm/m. drying shrinkage values were less than 0.5mm/m which was required in GB/T11968-2006.curing condition hadgreat influence on the performance of alkali activated almagnesium slag aerated concrete.When cured at 80? with humidity of 80% for five hours, the strength of alkali activated almagnesium slag aerated concrete can achieve the requirement of standard. The 60-daydrying shrinkage of specimen was over 2mm/m, while the porosity of the aerated concrete was between 75% and 85%. The moisture content was about 20%, and water absorption ranged from 85% to 125%, close to autoclave aerated concrete. The water free diffusion is obvious, and the water absorption coefficient can be used to analyze the durability of the concrete.The thermal conductivity of B06 concrete was 0.18 W/m?K, and thermal resistancewas 1.33m2?K/W. Compared with the conventionalwall materials, the aerated concrete produced in this study showed good heat preservation and heat insulation property. However, the thawing and freezing experiment indicated that there was great loss of mass and obvious decrease of strength after 15 cycles attributed to the large porosity, Therefore, the frost resistant property should be improved.The results of XRD and DSC-TG showed that the main hydration product was calcium silicate hydrate and calcium carbonate. FT-IR measurement demonstrated that the Si-O and Al-O bond was broken and condensed into new hydration products. Uniformly distributed ellipsoidal pores were observed by SEM, and the pore size was from 0.5mm to 1.5mm. |
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