【作者】 王云浩；

【导师】 管宗甫；

【作者基本信息】 郑州大学 ， 材料学， 2013， 硕士

【摘要】 烟气脱硫石膏,主要来源于燃煤电厂,我国众多的燃煤电厂每年产生大量的烟气脱硫石膏。脱硫石膏是一种优良的胶凝材料,主要应用在建筑行业；但是脱硫石膏制品耐水性能较差,这一缺陷限制了脱硫石膏的应用。在兼顾强度的同时,提高脱硫石膏制品的耐水性能,将会极大地拓展脱硫石膏的应用领域。本文主要研究提高脱硫石膏的耐水性能的措施。研究方法有以下几点：通过减少石膏制品内部孔隙率可以密实制品结构,这减少了拌合用水量,提高了强度和耐水性能；在石膏制品中引入防水材料,防水外加剂可以在建筑石膏颗粒表面形成一层致密的保护膜,改变建筑石膏与水的亲和性能,从而阻碍水分的渗入和破坏；在石膏制品中引入水硬性第二骨架可以有效地抵抗水分的破坏,从而提高耐水性能；同时本文还对免煅烧石膏基材料的耐水性能进行了初步探讨。通过研究得出了以下结论：(1)聚羧酸减水剂和脂肪族减水剂的加入可以有效地减少脱硫建筑石膏拌合用水量,从而改善其抗水性,在复掺缓凝剂的时候还可以有效延缓流动度经时损失。掺入这两种减水剂能够减少石膏制品的吸水率和提高绝干强度。同等掺量下聚羧酸减水剂对石膏制品吸水率的降低效果更好,而脂肪族减水剂对石膏制品强度的提高效果较优。石膏制品的软化系数随着这两种减水剂掺量的增加均先增大而后略有减小。当减水剂含量是1.6%时,软化系数都出现最大值0.75。(2)加入乙烯-乙酸乙烯脂共聚乳液或聚乙烯醇都可以一定程度上改善石膏制品的抗水性。随着这两种防水外加剂的加入,石膏制品的吸水率都先迅速降低而后降低趋势趋于平缓,聚乙烯醇对石膏制品吸水率的减小效果要好于乙烯-乙酸乙烯脂共聚乳液。石膏制品的绝干强度随着这两种防水外加剂掺量的增加先是逐步升高,之后强度却明显降低。石膏制品的软化系数随着聚合物掺量的增加先是快速升高,随后趋于稳定,当乙烯-乙酸乙烯脂共聚乳液和聚乙烯醇的掺量为4%的时候,石膏制品的抗压软化系数分别达到最大值0.80和0.83。(3)当在石膏粉煤灰体系和石膏矿粉体系中加入生石灰或水泥时,制品的吸水率都会有明显的降低,绝干抗压强度都会逐渐升高,并且软化系数均先线性增加而后增大趋势趋于平缓。石膏矿粉体系相对于石膏粉煤灰体系表现出更优良的力学性能。这是因为石膏矿粉体系在水泥或生石灰存在的条件下,矿粉的活性被较好地激发出来,与二水石膏一起生成了较多的水硬性产物。热分析和XRD分析表明,产物中有大量的二水石膏结晶,以及较多的C-S-H和少量的AFt。(4)掺加3%的水泥可以提高免煅烧脱硫石膏复合材料的抗压强度,最大抗压强度可以达到20.3MPa,但是随着水泥掺加量的增加,复合材料的抗压强度又逐步减小。免煅烧脱硫石膏复合材料在湿热养护时强度的发展好于在水中养护。这种材料的养护是在饱水的环境中进行的,因此使用在湿润的环境中也可以保持一定强度。更多还原

【Abstract】 Flue gas desulfurization gypsum mainly come from coal-fired power plant and China’s numerous coal-fired power plants produce large amounts of flue gas desulfurization gypsum every year. FGD gypsum which mainly used in the construction industry is an excellent cementitious material, but the application of FGD is large limitted because of it’s poor water resistance. Improving the water resistance and taking into account of the strength at the same time can greatly expand the applications of the FGD gypsum products.This paper mainly studies the measures to improve the water resistance of desulfurization gypsum. The research methods are as follow:Compacting the structure of FGD gypsum products can improve the strengh and water resistance by reducing the mixing water consumption; Introducing waterproof material into gypsum products. Waterproof admixture can form a dense protective film on the surface of the gypsum particles which change the affinity of the building plaster and water, thus the gypsum products can not be destruction by ingressing of the water; Introduct hydraulic skeleton into gypsum products can effectively resist the damage of the water, strong water resistance comes from cementitious products which is insoluble in water; The article also discussed water resistance of free calcined gypsum-based materials. The results show that:(1)Adding polycarboxylate superplasticizer and aliphatic superplasticizer can effectively reduce the mixing water of the desulfurization building gypsum, thereby improving its water resistance. Fluidity loss of desulfurization gypsum can be effectively delay by complex doped retarde.The incorporation of these two superplasticizer can reduce water absorption and increase dry strength of gypsum products. Polycarboxylate superplasticizer does well in reducing the water absorption and aliphatic superplasticizer exhibit better in improveing the strength of gypsum products under equal dosage. The softening coefficient of gypsum products increases in the beginning and then decreases slightly as superplasticizer dosage increase. When the superplasticizer content is1.6%, the softening coefficient reach to a maximum value of0.75.(2)EVA and PVA can both improves the water resistance of gypsum products to a certain extend. With the increase in the dosage of the two waterproof admixture, the water absorption of the gypsum products are rapidly reduced in the beginning and then decreased to flatten, dry strength increase gradually and then reduce significantly, and softening coefficient are rise rapidly at first and then stabilized. When the dosage of EVA and PVA are4%, the softening coefficien of the gypsum products reach to a maximum value of0.80and0.83.(3)The water absorption of the gypsum products reduces significantly,dry strength increases gradually and softening coefficient increase at first and then stabilize when quicklime or cement are added in the gypsum-fly ash system or the gypsum-slag system. Gypsum-slag system exhibit higher strength and better water resistance than gypsum-fly ash system when added the same dosage of cement or lime. A large amount of the hydraulic product are generate in the case of plaster exist as the activity of the slag is prefferably excited in the existing conditions of the cement or lime. Thermal analysis and XRD analysis show that there are a lot of gypsum as well as more C-S-H and a small amount of AFt.(4)Free calcined desulfurization gypsum composite materials exhibit high strength when3%cement are added, the maximum compressive strength can reach to20.3MPa, but strength reduces with more cement. Free calcined desulfurization gypsum composite strength exhibit higher strength in the curing of the hot and humid than in the curing of water. Considering that this material are curried in water-saturated environment, the materials can be used in amoist environment and maintain a certain strength.更多还原