Wang Yan, Chen Yahao, Guo Bingbing, Zhang Shaohui, Tong Yueping, Niu Ditao
College of Materials Science & Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
State Key Laboratory of Green Building in Western China, Xi'an University of Architecture and Technology, Xi'an 710055, China.
Materials (Basel). 2022 Apr 11;15(8):2790. doi: 10.3390/ma15082790.
The hydration process and compressive strength and flexural strength development of sulphate-resistant Portland cement (SRPC) curing at 20 °C, 40 °C, 50 °C, and 60 °C were studied. In addition, MIP, XRD, SEM, and a thermodynamic simulation (using Gibbs Energy Minimization Software (GEMS)) were used to study the pore structure, the types, contents, and transformations of hydration products, and the changes in the internal micro-morphology. The results indicate that, compared with normal-temperature curing (20 °C), the early compressive strength (1, 3, and 7 d) of SRPC cured at 4060 °C increased by 10.157.4%, and the flexural strength increased by 1.821.3%. However, high-temperature curing was unfavorable for the development of compressive strength and flexural strength in the later period (2890 d), as they were reduced by 1.514.6% and 1.125.5%, respectively. With the increase in the curing temperature and curing age, the internal pores of the SRPC changed from small pores to large pores, and the number of harmful pores (>50 nm) increased significantly. In addition, the pore structure was further coarsened after curing at 60 °C for 90 d, and the number of multiple harmful pores (>200 nm) increased by 17.9%. High-temperature curing had no effect on the types of hydration products of the SRPC but accelerated the formation rate of hydration products. The production of the hydration products C-S-H increased by 13.5%, 18.6%, and 22.8% after curing at 40, 50, and 60 °C for 3 d, respectively. The stability of ettringite (AFt) reduced under high-temperature curing, and its diffraction peak was not observed in the XRD patterns. When the curing temperature was higher than 50 °C, AFt began to transform into monosulfate, which consumed more tricalcium aluminate hydrate and inhibited the formation of “delayed ettringite”. Under high-temperature curing, the compactness of the internal microstructure of the SRPC decreased, and the distribution of hydration products was not uniform, which affected the growth in its strength during the later period.
研究了抗硫酸盐波特兰水泥（SRPC）在20℃、40℃、50℃和60℃养护时的水化过程以及抗压强度和抗折强度发展情况。此外，采用压汞法（MIP）、X射线衍射（XRD）、扫描电子显微镜（SEM）以及热力学模拟（使用吉布斯自由能最小化软件（GEMS））来研究孔隙结构、水化产物的类型、含量及转变情况，以及内部微观形貌的变化。结果表明，与常温养护（20℃）相比，4060℃养护的SRPC早期抗压强度（1、3和7天）提高了10.157.4%，抗折强度提高了1.821.3%。然而，高温养护不利于后期（2890天）抗压强度和抗折强度的发展，后期抗压强度和抗折强度分别降低了1.514.6%和1.125.5%。随着养护温度和养护龄期的增加，SRPC内部孔隙由小孔变为大孔，有害孔（>50nm）数量显著增加。此外，在60℃养护90天后，孔隙结构进一步粗化，多重有害孔（>200nm）数量增加了17.9%。高温养护对SRPC水化产物类型无影响，但加快了水化产物的生成速率。在40℃、50℃和60℃养护3天后，水化产物C-S-H的生成量分别增加了13.5%、18.6%和22.8%。高温养护下钙矾石（AFt）的稳定性降低，在XRD图谱中未观察到其衍射峰。当养护温度高于50℃时，AFt开始转化为单硫型水化硫铝酸钙，消耗了更多的水化铝酸三钙，抑制了“延迟钙矾石”的形成。高温养护下，SRPC内部微观结构的致密性降低，水化产物分布不均匀，影响了后期强度增长。
