纳米级掺合料和粗合成纤维对湿喷混凝土回弹率的影响
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摘要
降低喷射混凝土回弹率可提高支护效率、降低地下空间的坍塌及岩爆风险。为分析纳米级掺合料、粗合成纤维对喷射混凝土回弹率的影响,基于湿喷工艺对比了纳米级掺合料与同掺量硅灰在改善湿喷混凝土回弹率方面的差异;比较了不同纳米级掺合料掺量、细度条件下各湿喷混凝土的回弹率区别;研究了粗合成纤维掺量、长径比、混杂方式等对回弹率的影响。结果表明:应用纳米级掺合料有助于降低湿喷混凝土的回弹率;与同掺量硅灰相比,纳米级掺合料湿喷混凝土的回弹率降低了17%～25%,且回弹率随纳米级掺合料掺量提高、细度增加而降低。粗合成纤维可降低湿喷混凝土的回弹率,但受材质影响较小,存在较低回弹率的最佳长径比和掺量,分别为38和10 kg/m~3。长径比76和长径比30的2种粗合成纤维混杂使用时,可进一步降低回弹率。
Reducing the rebound rate of shotcrete can promote the efficiency of support and reduce the risks of collapse and rock burst for underground openings. To evaluate the effect of nanometer scale admixture( NSA) and macro synthetic fiber( MSF) on the rebound rate of wet-mix shotcrete( WMS),rebound rates were compared with each other based on wet sprayed technology among WMS with different cementing compositions such as introducing NSA or silica fume. The contents and fineness of NSA were also investigated when taking rebound rate as the main subject. Contents,aspect ratios and hybrid ways of MSF were discussed,too. The results indicated that NSA could reduce the rebound rate of shotcrete. The rebound rate of WMS could be reduced by about 17% to25% when silica fume was replaced by NSA totally. Besides,the rebound rate of WMS would further decrease with the increment of contents or fineness of NSA. Macro synthetic fiber had a part in reducing rebound rate. Although fiber nature had little effect on rebound rate,the aspect ratio and content of MSF couldn't be ignored,and its best values were 38 and 10 kg/m3,respectively. In addition,the rebound rate could be further reduced when WMS was optimized with hybrid MSF consisting of two kinds of fibers,whose aspect ratios were 76 and 30.
Reducing the rebound rate of shotcrete can promote the efficiency of support and reduce the risks of collapse and rock burst for underground openings. To evaluate the effect of nanometer scale admixture( NSA) and macro synthetic fiber( MSF) on the rebound rate of wet-mix shotcrete( WMS),rebound rates were compared with each other based on wet sprayed technology among WMS with different cementing compositions such as introducing NSA or silica fume. The contents and fineness of NSA were also investigated when taking rebound rate as the main subject. Contents,aspect ratios and hybrid ways of MSF were discussed,too. The results indicated that NSA could reduce the rebound rate of shotcrete. The rebound rate of WMS could be reduced by about 17% to25% when silica fume was replaced by NSA totally. Besides,the rebound rate of WMS would further decrease with the increment of contents or fineness of NSA. Macro synthetic fiber had a part in reducing rebound rate. Although fiber nature had little effect on rebound rate,the aspect ratio and content of MSF couldn't be ignored,and its best values were 38 and 10 kg/m3,respectively. In addition,the rebound rate could be further reduced when WMS was optimized with hybrid MSF consisting of two kinds of fibers,whose aspect ratios were 76 and 30.
引文
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[2]刘涛.太行山隧道进口工程湿喷微纤维混凝土的选择与施工[J].混凝土,2007(2):94-95.(LIU Tao.Selection and construction of wet basting microfibrils concrete in Taihang mountain tunnel entrance project[J].Concrete,2007(2):94-95.(in Chinese))
[3]漫玉见,余文胜,霍海平.湿喷钢纤维混凝土在公伯峡水电站导流洞工程中的应用[J].水力发电,2002(8):52-55.(MAN Yujian,YU Wensheng,HUO Haiping.Application of wet-spraying steel fiber concrete in the diversion tunnel project of Gongboxia Hydropower Station[J].Water Power,2002(8):52-55.(in Chinese))
[4]陈晓东.钢纤维喷射混凝土在隧洞加固处理中的应用[J].建筑技术,2003,34(6):440-441.(CHEN Xiaodong.The application of steel fiber sprayed concrete in the reinforcement of tunnel[J].Architecture Technology,2003,34(6):440-441.(in Chinese))
[5]何文敏.高含气量湿喷混凝土性能与组成设计方法研究[D].西安:长安大学,2014:78.(HE Wenmin.Study of properties and mix design of wet-mix shotcrete with high air content[D].Xi’an:Chang’an University,2014:78.(in Chinese))
[6]BINDIGANAVILE V,BANTHIA N.Rebound in dry-mix shotcrete:influence of type of mineral admixture[J].ACI Materials Journal,2000,97(2):115-119.
[7]TANG Ming,TONG Yu.Research on high-performance spray concrete[J].Journal of Shangdong institute of Building Materials,1998,12(Suppl1):149-153.
[8]PICKELMANN J,PLANK J.A mechanistic study explaining the synergistic viscosity increase obtained from polyethylene oxide(PEO)andβ-naphthalene sulfonate(BNS)in shotcrete[J].Cement and Concrete Research,2012,42(42):1409-1416.
[9]MARKUS P,WOLFGANG K.Rheology and rebound behaviour of dry-mix shotcrete[J].Cement and Concrete Research,2001,31(11):1619-1625.
[10]钱桂枫,高祥彪,钱春香.PVA纤维对混凝土力学性能的影响[J].混凝土与水泥制品,2010(3):52-54.(QIANGuifeng,GAO Xiangbiao,QIAN Chunxiang.Effects of PVA fiber on mechanical properties of concrete[J].China Concrete and Cement Products,2010(3):52-54.(in Chinese))
[11]蒋林华.混凝土材料学[M].南京:河海大学出版社,2006:400-402.(JIANG Linhua.Concrete materials science[M].Nanjing:Hohai University Press,2006:400-402.(in Chinese))
[12]梅国栋,李继祥,刘肖凡,等.混杂纤维混凝土增强机理研究综述[J].建材世界,2009,30(3):10-14.(MEIGuodong,LI Jixiang,LIU Xiaofan,et al.Review of the research and application about hybrid fiber reinforced concrete[J].The World of Building Materials,2009,30(3):10-14.(in Chinese))
[13]谢京辉,彭刚,陈灯红,等.不同初始孔隙水压力下混凝土动态力学特性[J].水利水运工程学报,2017(3):100-107.(XIE Jinghui,PENG Gang,CHEN Denghong,et al.Dynamic properties of concrete under different initial pore water pressure[J].Hydro-Science and Engineering,2017(3):100-107.(in Chinese))