隧道喷射混凝土防钙溶出复合掺和料的配制与性能研究

Preparation and Performance Study of Anti-calcium Dissolution Composite Admixture for Tunnel Shotcrete

针对隧道出现的钙溶出结晶现象,基于室内试验,通过测定胶砂试件的钙离子溶出量、抗压强度、抗折强度等指标,并结合扫描电子显微镜对微观形貌进行了表征,优选出几种隧道喷射混凝土防钙溶出复合掺和料配方。结果表明:复合掺和料在3种不同配比下均能改善胶砂试件的钙离子溶出性能,最大提升率为32.41%;3种配比下胶砂试件的抗压强度均有增强作用,28 d龄期抗压强度最高可达40.32 MPa,抗折强度也有明显提升效果,较普通胶砂试件增长率为25.4%~33.8%。从微观形貌观察到,掺入复合掺和料的水泥石内部致密,无明显可供侵蚀性介质渗入的毛细通道,水化产物多,且有凝胶体生成,填充了结构孔隙,从机理方面揭示了复合掺和料对隧道防结晶有明显作用。

In view of the phenomenon of calcium dissolution and crystallization in tunnels,this study conducted indoor experiments to determine the calcium ion leaching,compressive strength and flexural strength of mortar specimens,and combined with Scanning electron microscope to characterize the microscopic morphology.Several composite admixture formulations for preventing calcium leaching in tunnel shotcrete were selected.The results showed that the composite admixture can improve the calcium ion dissolution performance of the rubber sand specimen under three different ratios,with a maximum improvement rate of 32.41%;The compressive strength of the rubber sand specimens under three different ratios has been enhanced,with a maximum compressive strength of 40.32 MPa at 28 days,and a significant improvement in flexural strength,with a growth rate of 25.4%to 33.8%compared to ordinary rubber sand specimens.It can be seen from the microscopic appearance that the cement paste mixed with composite admixtures is dense inside,there is no obvious capillary channel for corrosive media to penetrate,there are many hydration products,and there is gel formation,filling the structural pores,which reveals that the composite admixtures have obvious effect on the crystallization prevention of tunnels from the mechanism.