Modification Of Polyvinyl Alcohol And Inorganic Materials On FGD Building Gypsum

Desulfurization building gypsum products have many excellent properties, such aslightweight, energy-saving, fire proof, heat insulation and sound insulation. But thehydration products low water-resistance and the actual consumption of water is muchlarger than the theory of water demand in the actual production, so its porosity increasedand strength and water resistance decreased significantly. Therefore, the application ofthe FGD building gypsum products were restricted. In this paper, the influences ofcomposite of fly ash, blast furnace slag,cement and polyvinyl alcohol on characteristicsof FGD building gypsum were studied.And the influence mechanism was studied. Themain works and achievements are as follows:1The influences of admixture replacement and admixture types of fly ash, blastfurnace slag and cement on characteristics of FGD building gypsum were studied. Theresults show that(1) Adding fly ash, adding fly ash and blast furnace slag(or cement) andadding fly ash, blast furnace slag and cement can prolong the setting time, adding fly ashand blast furnace slag can reduce the water requirement of normal consistency, on thecontrary, adding cement can increase the water requirement of normal consistency.(2)When the fly ash was added separately, strength and water resistance of the samplesdecreased with increase of fly ash content; when fly ash and blast furnace slag wereadded compositely, the strength of the samples decreased significantly and its waterresistance decreased firstly and then increased, with increase of blast furnace slag dosage;when fly ash and cement were added compositely, the strength of the samples decreasedand its water resistance increased firstly and then decreased, with increase of cementdosage.(3)As total amounts of admixtures are equivalent，the strength and waterresistance of adding cement and fly ash and adding fly ash, blast furnace slag and cementspecimens are higher than that of adding fly ash and adding fly ash and blast furnace slagspecimens, by adjusting the content of fly ash, blast furnace slag and cement.2The influences of polyvinyl alcohol emulsion on characteristics of FGD buildinggypsum were studied. The results show that(1)The setting time and the waterrequirement of normal consistency of FGD building gypsum increased due to the addingof polyvinyl alcohol emulsion.(2)The strength and softening coefficient of the samplesincreased firstly and then decreased, with increase of polyvinyl alcohol emulsion dosage. The strength of2h and softening coefficient of the samples were the highest when thedosage of polyvinyl alcohol emulsion was2%. The strength of28d of the samples werethe highest when the dosage of polyvinyl alcohol emulsion was6%.3The influences of composite of inorganic materials and polyvinyl alcoholemulsion on characteristics of FGD building gypsum were studied. The results show that(1) When the content of fly ash was10%, with increase of dosage of polyvinyl alcoholemulsion,the setting time and the water requirement of normal consistency of thesamples increased, the strength of2h and the compression softening coefficientdecreased. The strength of28d increased firstly and then decreased and was the highestwhen the dosage of polyvinyl alcohol emulsion was6%. The flexural softeningcoefficient was the highest when the dosage of polyvinyl alcohol emulsion was2%.(2)When the content of fly ash and cement was10%and7.5%respectively, with increase ofdosage of polyvinyl alcohol emulsion, the setting time of the samples increased firstlyand then decreased, and the water requirement of normal consistency of the samplesincreased, and the strength of2h decreased firstly and then changed mildly, the softeningcoefficient increased firstly and then decreased. The strength of28d was the highestwhen the dosage of polyvinyl alcohol emulsion was2%, and the softening coefficientwas the highest when the dosage of polyvinyl alcohol emulsion was6%.(3) When thecontent of fly ash, blast furnace slag and cement was10%,10%and5%respectively, withincrease of dosage of polyvinyl alcohol emulsion, the water requirement of normalconsistency of the samples increased firstly and then remained constant, the final settingtime of the samples increased firstly and then decreased, the initial setting time of thesamples increased,the strength of2h decreased firstly and then changed a little,and thestrength of28d and the softening coefficient were the highest when the dosage ofpolyvinyl alcohol emulsion was2%.(4)When the dosage of polyvinyl alcohol emulsionwas2%, the strength of2h was highest when the fly ash was added separately. When flyash, blast furnace slag and cement were added, the strength of28d and softeningcoefficient were the highest. When the dosage of polyvinyl alcohol emulsion was6%, thestrength of2h and28d was highest if the fly ash was added separately and the softeningcoefficient was highest if fly ash, blast furnace slag and cement were together added.