功能外加剂对隧道二次衬砌拱顶充填砂浆性能的影响

Effect of Functional Admixtures on the Performances of Mortars Filling behind Tunnel Vault Secondary Lining

为了解决隧道二次衬砌拱顶脱空等问题,基于铁路隧道二次衬砌充填砂浆基本性能要求,在OPC∶SAC=0.65∶0.35,胶砂比=0.55∶0.45,水料比为0.18,粉煤灰掺量为10%的基础上,通过流动度、泌水率、强度、膨胀性和干缩性等方面,开展功能外加剂对充填砂浆性能影响的研究。结果表明:酒石酸掺量为0.3%,碳酸锂掺量为0.2%,塑性膨胀剂掺量为0.06%,消泡剂掺量为0.15%,保水增稠剂掺量为0.12%,可制备出工作自密实、不泌水、不离析、早期强度高、后期强度高、微膨胀的充填砂浆;充填砂浆与衬砌混凝土结合性试验、施工现场雷达无损检测和拱顶钻芯结果表明,充填砂浆与隧道二次衬砌混凝土结合性好,可减少隧道二次衬砌背后脱空情况,避免了衬砌充填材料与二次衬砌混凝土"两张皮"现象。

As for the vault voids and other issues of tunnel secondary lining,based on the basic performance requirements for filling mortars of secondary lining of railway tunnels,and under mixture formula of OPC∶SAC=0.65∶0.35,cement∶sand=0.55∶0.45,water:aggregate=0.18 and 10%fly ash admixture,this paper studies the effect of functional admixtures on the performance of mortars in terms of the fluidity,bleeding rate,strength,expansibility and dry shrinkage,etc.The results show that:under the mixing dosages of 0.3%tartaric acid,0.2%lithium carbonate,0.06%plastic expander,0.15%defoamer and 0.12%water-retaining thickener,the filling mortar can be prepared with properties of self-compacting,no bleeding,no segregation,high early and long-term strength,and micro expansion;through the bonding test of filling mortar and lining concrete,field radar nondestructive testing and vault core drilling,the results show that there is a good bonding capability between the filling mortars and the tunnel secondary lining,which could mitigate voids behind tunnel secondary lining and avoid the separation between filling materials and secondary lining concrete.