水泥-凝灰岩-粉煤灰复合胶凝材料硬化浆体微观结构特征

摘要

利用X射线衍射(XRD)、热重(TG)、压汞法(MIP)、扫描电镜分析(SEM)等现代测试技术与方法对水泥-凝灰岩-粉煤灰复合胶凝材料硬化浆体微观结构特征进行测定和分析.结果显示:凝灰岩的掺入使得硬化浆体中引入了长石、水云母及低温型石英(α-SiO2)等晶相物质,其余水化产物与纯水泥样品基本相同;含有凝灰岩的水泥硬化浆体中Ca(OH)2含量降低幅度明显小于水泥-粉煤灰二元胶凝体系;随着养护龄期的延长,复合胶凝材料硬化浆体孔隙率逐渐降低,孔径逐步得到细化,到水化180 d时,各样品中最可几孔径的分布主要集中在4.5~50 nm,浆体结构朝着对耐久性有利的方向发展;凝灰岩颗粒特殊形貌引起的形态效应和微集料填充作用在水化初期显得较为明显;相比于同掺量情况下的单掺粉煤灰体系和单掺凝灰岩体系,水泥-凝灰岩-粉煤灰三元胶凝体系的水化产物较多,越来越多的凝灰岩和水泥的水化产物包裹粉煤灰球形颗粒,并逐渐形成整体,整个浆体微观结构结合紧密.%The microstructural characteristics of composite binders containing fly ash and(or) tuff powder were in-vestigated by XRD (X-ray diffractometer), TG (thermogravimetry), MIP (mercury intrusion method) and SEM (scanning electron microscopy). Results show that feldspar,hydromica and α-SiO2were produced in the hardened paste due to the incorporation of tuff powder,and the other hydration products in the hardened paste of composite binders were basically the same as those of pure cement pastes. The decline of Ca(OH)2content in the hardened cement paste containing tuff powder was significantly lower than that of cement-fly ash binary cementitious system. Moreover,the porosity of hardened pastes of complex binders decreased gradually and the pore size was gradually refined with the extension of curing age. The most probable aperture distribution of each sample hydrated for 180 days was mainly concentrated in 4.5 nm-50 nm,and the microstructure of hardened pastes of complex binders was developing in a direction favorable for durability. The morphology effect and micro-aggregate filling effect were caused by the special morphology of tuff granules,which were obvious in the early stage of hydration. The hydration product of the ternary cementitious system containing cement,tuff powder and fly ash were much more than that of the cement-fly ash binary system and the cement-tuff powder binary system with the same dosage.The spherical par-ticles of fly ash were encapsulated by hydration products of tuff powder and cement, making the microstructure of pastes combined closely.