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C50补偿收缩喷射混凝土的配合比设计及耐久性研究
作者：宁逢伟1，蔡跃波1，丁建彤2，张丰1，白银1，陈波1
（1.南京水利科学研究院 水文水资源与水利工程科学国家重点实验室，江苏 南京 210029；
2.中国水利水电第七工程局有限公司，四川 成都 611730）
摘要：常规C25喷射混凝土抗压强度低、耐久性差，难以满足高地应力条件下地下洞室的快速支护需求。为解决上述问题，通过降低水胶比、掺入活性掺合料、引入2%~6%氧化钙类膨胀剂对C50喷射混凝土进行配合比设计，并考察其力学、变形、抗渗和抗冻等性能。结果表明：采用10%硅灰、2%~4%氧化钙类膨胀剂、0.35水胶比、抗压强度比120%以上的无碱速凝剂可制备C50补偿收缩喷射混凝土。该混凝土的密实度和耐久性较高，孔隙率仅为常规C25喷射混凝土的44%~50%，80%左右孔隙的直径均在50 nm以内，抗渗等级和抗冻等级也已分别超过W25和F300。
关键词：喷射混凝土；高强；配合比设计；耐久性；孔结构
中图分类号：TU528.53 文献标识码：A 文章编号：1001-702X（2020）01-0001-05
Study on mix design and durability of C50 compensating-shrinkage shotcrete
NING Fengwei1，CAI Yuebo1，DING Jiantong2，ZHANG Feng1，BAI Yin1，CHEN Bo1
（1.Nanjing Hydraulic Research Institute，State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering，Nanjing 210029，China；
2.Sinohydro Bureau 7 Corporation Limited，Chengdu 611730，China）
2.Sinohydro Bureau 7 Corporation Limited，Chengdu 611730，China）
Abstract：Low compressive strength and poor durability were typical characteristics of ordinary C25 shotcrete，which made it difficult to meet the support requirement of underground openings in high ground stress conditions. In order to solve these problems，the mix design of C50 shotcrete was carried out by reducing water-binder ratio，adding active admixture and introducing 2%~6% of calcium oxide expansive agent. Mechanical properties，deformation and durability of C50 shotcrete were also evaluated. The results indicated that C50 compensating-shrinkage shotcrete could be made by using 10% of silica fume，2%~4% of calcium oxide expansive agent，water-binder ratio of 0.35 and alkali-free accelerator whose compressive strength ratio surpassed 120%. The shotcrete had higher compactness and durability. The porosity was only 44%~50% of that of ordinary C25 shotcrete. The diameters of around 80% of pores were less than 50 nm. Besides，the impermeability grade and freeze resistance grade surpassed W25 and F300，respectively.
Key words：shotcrete，high strength，mix design，durability，pore structure