Li Yongqiang, Luo Yaoming, Du Hangyu, Liu Wei, Tang Luping, Xing Feng
Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen University, Shenzhen 518060, China.
Key Laboratory for Resilient Infrastructures of Coastal Cities (Ministry of Education), College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China.
Materials (Basel). 2022 Sep 1;15(17):6037. doi: 10.3390/ma15176037.
The microstructural evolutions of both uncarbonated and carbonated cement pastes subjected to various high temperatures (30 °C, 200 °C, 400 °C, 500 °C, 600 °C, 720 °C, and 950 °C) are presented in this study by the means of mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). It was found that the thermal stabilities of uncarbonated cement pastes were significantly changed from 400 to 500 °C due to the decomposition of portlandite at this temperature range. More large pores and microcracks were generated from 600 to 720 °C, with the depolymerization of C-S-H. After carbonation, the microstructures of carbonated cement pastes remained unchanged below 500 °C and started to degrade at 600 °C, due to the decompositions of calcium carbonates and calcium modified silica gel. At 950 °C, both uncarbonated and carbonated cement pastes showed a loosely honeycombed microstructure, composed mainly of β-CS and lime. It can be concluded that carbonation improves the high-temperature resistance of cement pastes up to 500 °C, but this advantage is lost at temperatures over 600 °C.
本研究通过压汞法（MIP）和扫描电子显微镜（SEM），展示了未碳化和碳化水泥净浆在不同高温（30℃、200℃、400℃、500℃、600℃、720℃和950℃）下的微观结构演变。结果发现，由于在此温度范围内氢氧化钙的分解，未碳化水泥净浆的热稳定性在400至500℃时发生了显著变化。在600至720℃时，随着C-S-H的解聚，产生了更多的大孔隙和微裂纹。碳化后，碳化水泥净浆的微观结构在500℃以下保持不变，在600℃时开始降解，这是由于碳酸钙和钙改性硅胶的分解。在950℃时，未碳化和碳化水泥净浆均呈现出主要由β-CS和石灰组成的松散蜂窝状微观结构。可以得出结论，碳化可提高水泥净浆在500℃以下的耐高温性，但在温度超过600℃时这种优势丧失。
