减缩抗裂型水泥基材料及其工程应用

设计了干燥收缩、自生收缩、椭圆环约束等试验手段,研究了矿物质微膨胀剂、硅灰和减缩剂对水泥基材料体积稳定性的影响及其作用机理。试验结果表明:(1)矿物质微膨胀剂具有较强的收缩补偿作用,随其掺量的增加,干燥收缩与自生收缩降低,当掺量为25%时,可使初始开裂时间延长至82 h。(2)随硅灰掺量的增加,干燥收缩和自生收缩增大,当掺量为10%时,初始开裂时间降低至22 h,此时开裂敏感性最大,因此硅灰掺量应合理控制。(3)减缩剂可以大幅度降低砂浆的开裂敏感性,且与其他外加剂相容性良好,对养护温度变化不敏感。由此,设计制备出一种用于重大工程结构混凝土保护层的体积稳定性优良的减缩抗裂型水泥基材料。此外还介绍了"矿物质微膨胀剂-减缩剂-混杂纤维"裂缝控制技术在武汉长江隧道工程中的应用情况。

Shrinkage-reducing Crack-resistant Cement-based Material and Its Application

Three check-up experiments including drying shrinkage,autogenous shrinkage,elliptical ring restraint were designed to investigate the effect of mineral micro-expansion agent,shrinkage-reducing agent and silica fume on volume stability of cement-based materials and their mechanisms.Results show that:(1) Mineral micro-expansion agent has stronger shrinkage-compensating effect,drying and autogenous shrinkage decreases with increase of mineral micro-expansion agent.When its quantity is 25%,initial cracking time is extended to 82 hours.(2) Drying and autogenous shrinkage increases with the silica fume content.When its quantity is 10%,initial cracking time is reduced to 22 hours,and cracking sensitivity achieves maximum.Thereby the quantity of silica fume should be properly controlled.(3) Shrinkage-reducing agent which is not susceptible to temperature fluctuation can decrease cracking sensitivity of mortar significantly,and it has excellent compatibility with other admixtures.On this basis,a shrinkagereducing crack-resistant cement-based materials was developed.With excellent volume stability,it could be applied in concrete cover of the significant project.Furthermore,the application of crack control technology in Changjiang Tunnel Engineering in Wuhan was also introduced,which was based on "mineral micro-expansion agent-shrinkage-reducing agent-hybrid fiber".