Dissertation > Industrial Technology > Chemical Industry > Silicate > Artificial stone and other cementitious materials > Gypsum and its products > Basic theory

Research on the Modified Aerated Blocks of Flue Gas Desulfurization Gypsum

Author LaoYouSheng
Tutor YangJiuJun
Course Materials Science
Keywords FGD gypsum mechanical properties apparent density fly ash blastfurnace slag aerated block
CLC TQ177.31
Type Master's thesis
Year 2014
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Utilization of flue gas desulfurization (FGD) gypsum is a significant researchtopic. Like with natural gypsum, products made from FGD gypsum has excellentthermal insulation properties, adjust the indoor humidity and have excellentfireproofing performance. Aerated blocks made from FGD gypsum are much lighterand better thermal insulation. In this paper, firstly, the fly ash-desulfurization ofbuilding gypsum system and blast furnace slag (BFS)-desulfurization of buildinggypsum system which the mass ratio of gypsum exceeds80%were explored.Secondly the best conditions of aluminum gas evolution process of pure gypsum weredetermined. Thirdly, based on the above two studied, the mechanical properties,microstructure, macro pore structure and mechanism fly ash and blast furnace slag fordesulfurization gypsum of aerated block were studied. The results of all theexperiments showed that:(1) When FA content is14%, the strength reach21.1MPa, increased by about60%than pure gypsum and its main mechanism was physical filling effect of theenhancement of glass beads;(2) When BFS content is16%, the strength reach30.1MPa, increased by about100%than pure gypsum and its main mechanism was the cementation of BFShydration (mainly calcium silicate hydrates);(3) Under these conditions(W/G is0.6, aluminum content is0.2%, lime contentis6%, citric acid content is0.01%, mixing water temperature is40℃), the resultingapparent density and strength of gypsum aerated blocks were544kg/m~3and1.00MParespectively;(4) Lower W/G, as well as lowering the temperature increased dosage of limecould gave high apparent density and strength of aerated block, aerated block aperturewith the decrease of apparent density increases and a large increase in the connectivitybetween the holes, the number of independent closed pores decreased when theapparent density is reduced to500kg/m~3or less;(5) The strength of aerated blocks are directly related to the apparent density, andthe relationship between compressive strength and apparent density can berepresented by the equation: p=-0.23194+0.25864e(x/353.14)(P is the compressivestrength, x is apparent density), according to this expression, to get a lightweight, highstrength blocks must be doped with other admixtures to change the internal structure; (6) Doped with FA, the apparent density of aerated blocks were maintained at500kg/m~3or less, while the strength lower than pure gypsum about20%, onlyreached0.81MPa, so the enhanced mechanism can’t be preserved;(7) Doped with BFS, the apparent density of aerated blocks were maintained at530kg/m~3or less, while the strength higher than pure gypsum about60%, reach1.60MPa, and the enhanced mechanism can be preserved;(8) After wet and heated curing, the compressive strength of aerated blocks arereduced, and the decreasing of FA was larger than the BFS, cause the number ofcontact points was reduced, the cementation of FA and BFS hydration products wasweaker, but the macro pore structure has not changed greatly.

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