不同CO2养护压力下硫铝酸盐和硅酸盐水泥浆体早期微观结构

研究硫铝酸盐和硅酸盐水泥（CSA-OPC）浆体在不同碳养护压力下的早期碳化过程，通过X射线衍射、红外光谱、热重、压汞和扫描电镜等测试方法，表征碳化前后水泥浆体的物相组成和微观结构. 实验结果表明，CSA-OPC浆体的水化产物主要为钙矾石，碳化作用使钙矾石转变为碳酸钙和硫酸钙晶体；水泥中碳酸钙以3种晶型存在，其中方解石为主要存在形式. 碳化使半碳型的水化硫铝酸钙（Hc-AFm相）逐渐转化为单碳型的水化硫铝酸钙（Mc-AFm相），碳化程度和碳化深度随着碳化压力的增加而递增. 碳化后CSA-OPC水化产物体积减小，样品总孔隙率增大、孔隙结构变疏松. 研究结果阐明了CSA-OPC浆体在早期碳化养护条件下的微结构变化过程，为制备基于硫铝酸盐水泥的高效碳汇材料提供了技术支撑.

Microstructure of early-age calcium sulphoaluminate and ordinary Portland cement paste cured under different CO2 pressures

Carbonation process of calcium sulphoaluminate and ordinary Portland cement (CSA-OPC) paste under different carbon curing pressures at early age was investigated. X-ray diffraction, infrared spectroscopy, thermogravimetry, mercury intrusion porosimetry, and scanning electron microscopy were used to characterize the phase composition and microstructure of the paste before and after carbonation. Experimental results show that ettringite is the main hydration product of the CSA-OPC paste. After carbonation, ettringite is converted to calcium carbonate and calcium sulfate crystals. Calcium carbonate exists in three crystal forms in the paste, among which calcite is the main crystal. In addition, hemi-carbonate calcium sulfoaluminate hydrates (Hc-AFm) transfers to mono-carbonate calcium sulfoaluminate hydrates (Mc-AFm) after carbon curing. Carbonation degree and depth increase with the carbonation pressure. CSA-OPC hydration products’ volume decreases after carbonation, resulting in the increased total porosity and loose pore structure. The findings explore the microstructure alteration of CSA-OPC under early-age carbon curing, and provide a technique route for the fabrication of carbon-sinking materials based on calcium sulphoaluminate cement.