Characteristic and optimization of ferrite-rich sulfoaluminate-based composite cement suitable for cold region tunnels

适用于寒区隧道的铁铝酸盐基复合水泥性能及其改良

To develop suitable grouting materials for water conveyance tunnels in cold regions,firstly,this study investigated the performance evolution of ferrite-rich sulfoaluminate-based composite cement(FSAC grouting material)at 20 and 3℃.The results show that low temperature only delays the strength development of FSAC grouting material within the first 3 d.Then,the effect of four typical early strength synergists on the early properties of FSAC grouting material was evaluated to optimize the early(£1 d)strength at 3℃.The most effective synergist,Ca(HCOO)_(2),which enhances the low-temperature early strength without compromising fluidity was selected based on strength and fluidity tests.Its micro-mechanism was analyzed by XRD,TG,and SEM methods.The results reveal that the most suitable dosage range is 0.3 wt%−0.5 wt%.Proper addition of Ca(HCOO)_(2)changed the crystal morphology of the hydration products,decreased the pore size and formed more compact hydration products by interlocking and overlapping.However,excessive addition of Ca(HCOO)_(2)inhibited the hydration reaction,resulting in a simple and loose structure of the hydration products.The research results have reference value for controlling surrounding rock deformation and preventing water and mud inrushes during the excavation in cold region tunnels.

注浆是抽水蓄能电站输水隧洞施工中控制围岩变形、防止水泥侵入的重要技术。但在注浆工程中,低温严重阻碍了注浆材料强度的提高。此外,在低温条件下加入早强增效剂优化注浆材料性能的研究还很匮乏。为了开发适用于寒冷地区输水隧洞的注浆材料,本文首先研究了铁铝酸盐基复合水泥(FSAC注浆材料)在20℃和3℃下的性能演变。结果表明,低温只会延迟FSAC注浆材料在水化前3天的强度发展。随后评估了四种典型的早强增效剂对FSAC注浆材料早期性能的影响,以优化3℃下的早期(≤1 d)强度。基于强度和流动性测试选择出了最有效的早强增效剂为甲酸钙,它可以在不影响流动性的情况下提高低温条件下的早期强度。最后采用XRD、TG和SEM等方法对其微观机理进行了分析。实验结果表明,最合适的甲酸钙掺入量为0.3 wt%-0.5 wt%。适当添加甲酸钙改变了水化产物的晶体形态,减小了孔径,通过互锁和重叠形成了更致密的水化产物。然而过量添加甲酸钙则抑制了水化反应,导致水化产物结构简单疏松。本研究成果对寒区隧道开挖过程中控制围岩变形、防止突水突泥灾害具有参考价值。