脱硫石膏对污泥灰胶凝体系强度及微观结构的影响

Effect of Desulphurization Gypsum on the Strength and Microstructure of the Sludge Ash Cementitious System

为实现生活污泥灰的资源化利用,结合净浆强度测定、X射线衍射、红外光谱、热重分析及扫描电镜等手段,研究脱硫石膏对不同龄期污泥灰胶凝体系强度及微观结构的影响。结果表明:污泥灰胶凝体系水化产物主要为钙矾石、羟钙石和水化硅铝(铁)酸钙凝胶,脱硫石膏促进了胶凝体系早期的水化,生成更多水化产物,并提高了水化凝胶聚合度及试样抗压强度;水化后期,脱硫石膏加速了胶凝体系的碱激发反应,促使更多凝胶相生成。污泥灰-水泥胶凝体系微观结构以发育程度较低的颗粒状产物为主,存在较多孔隙,掺加脱硫石膏后,水化产物中板状氢氧化钙及针状钙矾石晶体填充于水化硅铝(铁)酸钙凝胶孔隙中,提高了试样结构密实度及宏观强度。

In order to realize the resource utilization of sewage sludge ash,the effect of desulphurization gypsum on the strength and hydration products of the sewage sludge ash cementitious system at different stages was studied by means of paste strength measurement,X-ray diffraction,infrared spectroscopy,thermogravimetric analysis and scanning electron microscopy.The result showed that the hydration products of the sewage sludge ash cementitious system were mainly ettringite,portlandite and hydrated silicon aluminum(iron)calcium gel.Desulphurization gypsum promoted the early hydration of calcium silicate in the cementitious system,generated more hydration products,and improved the degree of polymerization of the hydrated gel and strength of the sample;at the later stage of hydration,desulphurization gypsum accelerated the alkali-induced reaction of cementitious system,promoting the formation of more gel phase.The microstructure of the cementing system was mainly composed of granular products with low development degree,and there were many holes in the structure.After adding desulfurization gypsum,a large number of plate-like calcium hydroxide and short rod ettringite crystals were produced,interlacing and filling in the interlayer space of the gel,which improved the compactness of microstructures and macroscopic strength.