PC-CSA复合水泥收缩特性与微观结构

为了解决水泥混凝土普遍存在的收缩开裂问题,研究了硅酸盐-硫铝酸盐(Portland cement and calcium sulfoaluminate cement,PC-CSA)复合水泥化学收缩、自收缩和干燥收缩的机理及影响因素,通过微观形貌扫描电子显微镜(scanning electron microscope,SEM)、孔结构分析等手段对复合水泥浆体微观结构进行表征,对比普通硅酸盐水泥与PC-CSA复合水泥,揭示了不同矿物组成的水泥基材料的收缩特性与水泥基材料微观结构的对应关系.结果表明:化学收缩直接由水泥矿物组成决定,相比于自收缩,膨胀组分的加入对干燥收缩的影响最小.自收缩特性同时受到水泥内部相对湿度和水化产物组成及结构的影响.运用SEM图像定量分析水泥的孔隙率,通过此研究得到了一个图像选取区域的最佳范围:矿物30%~45%,该范围与水泥水化程度密切相关.分析了水化过程中水泥浆体孔结构的变化规律,发现膨胀组分的加入会改变水泥初期孔结构,同时验证了水化1d时复合水泥表现出明显的微膨胀现象,与实际测量的体积变化规律吻合.

Shrinkage Characteristics and Microstructure of Portland and Calcium Sulfoaluminate Composite Cement

In order to solve the problems of shrinkage and creep in concrete, a research of mechanism and impact factors of chemical shrinkage, autogenous shrinkage and drying shrinkage in PC-CSA composite cement,was conducted in this paper. SEM and MIP were used to perform the properties of Portland cement and calcium sulfoaluminate composite cements. The relationship between shrinkage of microstructure and strength,and the effects of cement phase content were discussed though a comparative study between OPC and PC-CSA composite cement. Results show that chemical shrinkage can be changed directly by adding expansive components. The effects of autogenous shrinkage are bigger than that of drying shrinkage. There is a new method to testing porosity by SEM. The critical range of the best yield of unhydrated cement mineral is 30% -45% obtained fromcomparing the results of MIP. The pore structure is changed and micro-expansion appears by adding expansive components at hydration one day. It is consistent with the actual measurement results of cement volume changes.