机制砂制备自流平混凝土在成自铁路隧道二衬中的应用

Application of Self-leveling Concrete Prepared by Machine-made Sand in the Secondary Lining of Chengzi Railway Tunnel

本文结合自密实混凝土的性能及隧道二衬的施工环境,通过优化混凝土配合比及使用减水剂,成功设计并制备了机制砂的自流平二衬混凝土。结果表明:随着混凝土配合比中水胶比的增大,混凝土的扩展度变小,T 500减少,泵送压力先降低再增大;随着混凝土配合比中砂率的增大,混凝土的扩展度先增大后减小,T 500及泵送压力则先减少再增大。优化后的混凝土配合比在成自铁路老罐石二号隧道中进行施工应用试验,其中,自密实二衬混凝土的胶凝材料用量428 kg/m^(3),粉煤灰掺量25%,机制砂的细度模数3.1,砂率44%,三种粒径分别为5~10 mm、10~16.5 mm和16~25 mm的碎石按1∶5∶4的比例组合,水胶比0.38,设计容重2400 kg/m^(3)。制备的自流平混凝土相较于普通混凝土,其坍落度及扩展度更大,混凝土粘聚性良好,泵送阻力较小,砂浆及浮浆层厚度较小,强度分布更均匀,能更好地应用于隧道二衬施工。

This paper combines the performance of self-compacting concrete and the construction environment of tunnel secondary lining,and successfully designs and prepares self-leveling secondary lining concrete with mechanism sand by optimizing the concrete mix proportion and using water reducing agents.The results show that as the water cement ratio in the concrete mix ratio increases,the expansion of the concrete decreases,the T500 time decreases,and the pumping pressure first decreases and then increases;as the sand content in the concrete mix ratio increases,the expansion of concrete first increases and then decreases,while the T500 time and pumping pressure first decrease and then increase.The optimized concrete mix ratio was used for construction and application experiments in the No.2 tunnel of the Chengzi railway.The cementitious material used in the self-compacting secondary lining concrete was 428 kg/m3,the fly ash content was 25%,the fineness modulus of the machine made sand was 3.1,and the sand ratio was 44%.Three types of crushed stones with particle sizes of 5~10 mm,10~16.5 mm,and 16~25 mm were combined in a ratio of 1∶5∶4,with a water cement ratio of 0.38 and a design bulk density of 2400 kg/m3.Compared with ordinary concrete,self-leveling concrete prepared has a higher slump and expansion,good concrete cohesion,lower pumping resistance,smaller mortar and floating slurry layer thickness,and more uniform strength distribution,which can be better applied in tunnel lining construction.