膨胀剂和硅灰改善C50喷射混凝土抗渗性能的研究

Research on Impermeability Improvement of C50 Shotcrete with Expansive Agent and Silica Fume

抗渗性差是喷射混凝土的突出问题,也是衬砌结构普遍渗漏水的主要原因之一。为提高抗渗性,将C50喷射混凝土作为研究对象,测试其抗渗等级、渗水高度和电通量,考察膨胀剂和硅灰对抗渗性的影响,并凭借孔结构分析、SEM等微观测试手段分析膨胀剂和硅灰的改善机理。结果表明:单掺10%硅灰可将抗渗等级提高至W25以上。采用2%~6%膨胀剂与10%硅灰复掺可进一步改善抗渗性,渗水高度降低75%~87%、电通量降低20%~34%、孔隙率降低3%~14%。微观分析表明:膨胀剂和硅灰改善喷射混凝土的抗渗性主要通过填充和挤密作用。硅灰具有显著的微细填充特征,当膨胀剂与硅灰复掺时,膨胀剂水化后总体积增加,所增加体积的一部分与硅灰形成叠加填充效应,其余部分在约束作用下可发挥一定的挤密效应。

Poor impermeability is a prominent problem of shotcrete and one of the main reasons for the general leakage of lining structure.In order to improve the impermeability,C50 shotcrete was taken as the research object,its impermeability grade,depth of water penetration and electric flux were tested,the influence of expansive agent and silica fume on impermeability was investigated,and the improvement mechanism of expansive agent and silica fume was analyzed by means of pore structure analysis and SEM.The results show that the impermeability grade of shotcrete can be increased to more than W25 using 10%of silica fume.The impermeability can be further improved when 2%-6%of expansive agent was together used with 10%of silica fume.The depth of water penetration,electric flux and porosity are reduced by 75%-87%,20%-34%and 3%-14%respectively.Results of microscopic analysis indicate that expansive agent and silica fume improve the impermeability of shotcrete mainly through filling effect and compaction effect.Silica fume has remarkable characteristics of filling fine pores.The filling effect can be strengthened when expansive agent is together used with silica fume because the volume of expansive agent increased after its hydration.Besides,the rest of the increased volume contribute to a certain compaction effect under constraint,which improve the impermeability of shotcrete together with filling effect.