高耐久性喷射混凝土的研究

发布时间：2018-04-21 05:19

本文选题：无碱速凝剂 + 喷射混凝土　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：喷射混凝土自从问世以来,由于其施工方法简单方便、工期短、适应性强且抗渗性好等优点,被广泛应用于各种隧道工程和支护工程。但是工程中喷射混凝土往往存在速凝剂腐蚀性强、回弹率大、后期强度下降严重以及耐久性差的问题,尤其是碱集料反应发生率较高。近年来人们开始对这些问题展开研究,希望解决喷射混凝土现阶段存在的问题。本文分析了喷射混凝土存在的问题,认为采用无碱速凝剂替代传统的粉末状速凝剂,可以改善喷射混凝土回弹大、速凝剂腐蚀性强以及后期强度降低的问题。并对掺入硅灰、粉煤灰、膨胀剂、减缩剂、引气剂和高模量聚丙烯腈纤维的喷射混凝土的耐久性进行探索,配制出凝结时间短、早期收缩小、抗渗好、抗冻好的高耐久喷射混凝土。通过试验研究发现:加入无碱速凝剂后水泥净浆的初终凝时间分别为2min25s和5min09s,喷射混凝土28d抗压强度是普通混凝土的97.4%,各项性能均有所提高。粉煤灰显著影响喷射混凝土的抗渗性和早期自收缩,有效改善喷射混凝土的抗渗性,抑制早期自收缩,最佳掺量为15%;减缩剂和膨胀剂可以有效地抑制喷射混凝土的自收缩和干燥收缩,预防喷射混凝土开裂,最佳掺量分别为1%和6%;引气剂对喷射混凝土的抗冻性有显著影响,明显改善了喷射混凝土的抗冻性,最佳掺量为0.02%;掺量为1kg/m3高模量聚丙烯腈纤维对喷射混凝土的自收缩有明显的改善,24h自收缩率减小26.9%,同时也改善了干缩和抗冻性,会使喷射混凝土的抗渗性不利,但影响并不大。
[Abstract]:Since its inception, shotcrete has been widely used in various tunnel and support projects because of its simple and convenient construction method, short construction period, strong adaptability and good impermeability. However, shotcrete often has some problems, such as strong corrosiveness of accelerator, large rebound rate, serious decline of later strength and poor durability, especially the occurrence rate of alkali aggregate reaction is high. In recent years, people began to study these problems, hoping to solve the existing problems of shotcrete at the present stage. In this paper, the problems of shotcrete are analyzed, and it is considered that the use of alkali free accelerator instead of traditional powder accelerator can improve the problems of high springback, strong corrosiveness of speeder and lower strength in the later stage of shotcrete. The durability of sprayed concrete mixed with silica fume, fly ash, expansion agent, shrinkage reducer, air entraining agent and high modulus polyacrylonitrile fiber is explored, and the setting time is short, the early shrinkage is small, and the impermeability is good. High durability sprayed concrete with good frost resistance. The experimental results show that the initial and final setting time of cement paste is 2min25s and 5 min 09s, respectively. The compressive strength of sprayed concrete for 28 days is 97.4 of ordinary concrete, and the properties are improved. Fly ash significantly affects the impermeability and early self-shrinkage of shotcrete, effectively improves the impermeability of shotcrete, and inhibits the early self-shrinkage. The optimum dosage is 15. The shrinkage reducing agent and expansion agent can effectively suppress the autogenous shrinkage and dry shrinkage of sprayed concrete and prevent the crack of shotcrete, the optimum dosage is 1% and 6% respectively. The air-entraining agent has a significant effect on the frost resistance of shotcrete. The freezing resistance of shotcrete was obviously improved, the optimum content was 0.02, and the content of 1kg/m3 high modulus polyacrylonitrile fiber significantly improved the self-shrinkage of sprayed concrete in 24 hours. At the same time, the shrinkage and frost resistance of sprayed concrete were also improved by 26.9%, and the dry shrinkage and freezing resistance were also improved by the addition of 1kg/m3 high modulus polyacrylonitrile fiber. It will make the impermeability of shotcrete unfavorable, but the influence is not great.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528.53

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