Jin Bingxin, Wu Shuanglei, Fan Shujing, Hang Fafu, Chen Huxing
School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China.
Linhai Zhongxin New Building Materials Co., Ltd., Taizhou 317000, China.
Materials (Basel). 2024 Nov 25;17(23):5766. doi: 10.3390/ma17235766.
Low-heat expansive cement (LHEC) is an environmentally friendly and low-carbon cementitious material. Compared to ordinary Portland cement (OPC), LHEC reduces CO emissions from the cement production process; furthermore, it enhances the service life of the cement by overcoming the problem of OPC's strength inversion in hot and humid environments. In order to improve the performance of LHEC in a hygrothermal environment, the strength and expansion of LHEC with different gypsum dosages (8-20%) at curing temperatures of 20 °C, 50 °C, and 80 °C were investigated. The corresponding mechanism was investigated using XRD, TGA, SEM, and porosity analyses. The results indicate that there is a 'critical gypsum dosage' for strength at 20 °C. The 'critical dosage' rises with the curing temperature or an increase in age. Raising the curing temperature has a better effect on the strength of cement with a higher gypsum dosage; it does not have such a positive effect on cement with a low gypsum dosage. The higher the gypsum content, the greater the expansion rate, and the longer the time needed for the expansion to stabilize. The higher the curing temperature, the shorter the time required for stable expansion and the lower the final expansion rate. Increasing the gypsum dosage and maintaining the temperature promote the hydration of slag and the formation of ettringite (AFt), thereby enhancing the microstructure of the cement. AFt decomposition occurs in the case of a low gypsum dosage and high curing temperature. According to the above results, it is inferred that the strength and expansion performance of LHEC in a hygrothermal environment can be improved by appropriately increasing its gypsum dosage. This finding offers valuable insights for the improvement of LHEC and its application in hygrothermal conditions.
低热膨胀水泥（LHEC）是一种环保型低碳胶凝材料。与普通硅酸盐水泥（OPC）相比，LHEC减少了水泥生产过程中的二氧化碳排放；此外，它还克服了OPC在高温高湿环境下强度倒缩的问题，从而延长了水泥的使用寿命。为了提高LHEC在湿热环境中的性能，研究了不同石膏掺量（8%-20%）的LHEC在20℃、50℃和80℃养护温度下的强度和膨胀性能。采用XRD、TGA、SEM和孔隙率分析等方法研究了相应的机理。结果表明，在20℃时，强度存在一个“临界石膏掺量”。“临界掺量”随养护温度或龄期的增加而升高。提高养护温度对高石膏掺量水泥的强度有较好的影响；对低石膏掺量水泥则没有这种积极影响。石膏含量越高，膨胀率越大，膨胀稳定所需时间越长。养护温度越高，膨胀稳定所需时间越短，最终膨胀率越低。增加石膏掺量并保持温度可促进矿渣的水化和钙矾石（AFt）的形成，从而增强水泥的微观结构。在低石膏掺量和高养护温度的情况下会发生AFt分解。根据上述结果推断，适当增加LHEC的石膏掺量可以改善其在湿热环境中的强度和膨胀性能。这一发现为LHEC的改进及其在湿热条件下的应用提供了有价值的见解。
