Ling Xuepeng, Wu Quande, Yang Jie, Wang Wenzheng, Liu Dagang, Zhang Yiteng
Key Laboratory of Transportation Tunnel Engineering of Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China.
School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China.
Materials (Basel). 2023 Mar 8;16(6):2165. doi: 10.3390/ma16062165.
The alkali-free accelerator based on aluminum sulfate is widely used in shotcrete in tunnels. Long-term Ca-leaching of shotcrete may adversely affect the tunnels in a water-rich mountain. It is necessary to examine further the impact of the AS accelerator and / on cement hydration and leaching. In this study, all the cement pastes were cured in the environment with R.H. > 95% and 20 ± 1 °C for 60 days and leached in a running water test with 6 M NHCl at 1 cm/s. The hydration kinetics was characterized by isothermal calorimetry. Additionally, the microstructural and mineralogical alterations were characterized by XRD, SEM, MIP, and N absorption. The results show that (1) the AS accelerator affected the hydration kinetics of cement by stimulating early hydration and delaying the late silicate hydration, resulting in AS-accelerated cement pastes with rougher pore structure. As a result, the higher the dose of AS accelerator, the faster the cement pastes will leach. (2) Hydration kinetics of the accelerated cement are not affected by the /. The AS-accelerated cement pastes with lower / have a denser pore structure. So, the reduction in the / contributes to leaching resistance.
基于硫酸铝的无碱速凝剂在隧道喷射混凝土中广泛应用。喷射混凝土长期的钙溶出可能会对富水山区的隧道产生不利影响。有必要进一步研究硫酸铝速凝剂和/或其对水泥水化及溶出的影响。在本研究中，所有水泥净浆在相对湿度>95%、20±1℃的环境中养护60天，并在流速为1cm/s的6M NHCl流水试验中进行溶出试验。水化动力学通过等温量热法表征。此外，微观结构和矿物学变化通过XRD、SEM、MIP和氮吸附进行表征。结果表明：（1）硫酸铝速凝剂通过促进早期水化和延缓后期硅酸盐水化影响水泥的水化动力学，导致硫酸铝速凝水泥净浆的孔结构更粗糙。因此，硫酸铝速凝剂的剂量越高，水泥净浆的溶出速度越快。（2）加速水泥的水化动力学不受/的影响。/较低的硫酸铝速凝水泥净浆具有更致密的孔结构。所以，/的降低有助于提高抗溶出性。
