高含气量湿喷混凝土性能与组成设计方法研究

发布时间：2018-10-30 19:02

【摘要】：湿喷混凝土因具有改善施工作业环境、便于混凝土集中生产及质量控制、有利于发展成高性能喷射混凝土等优越性而备受关注，但其可压送性与可喷性难以协调、组成设计无章可循，可压送性差、一次喷射厚度小、回弹率高、液体速凝剂掺量大等缺陷极大限制了它在当今基础设施建设中的广泛应用。本文就普通湿喷混凝土与高含气量湿喷混凝土的工作性及硬化特性、组成设计方法进行了系统研究，主要做了下列工作：（1）优化了新拌湿喷混凝土一次喷射厚度、回弹率等性能测评方法，提出了用椎体贯入新拌混凝土深度表征湿喷混凝土稠度、用直剪法测试新拌湿喷混凝土内聚力的新方法。（2）将入湿喷机坍落度≮50mm且相对压力泌水率S10≯40%作为普通湿喷混凝土可压送性的评价指标，研究了组成材料对普通湿喷混凝土可压送性的影响。结果表明，新拌湿喷混凝土的压力泌水率比易于满足要求，影响新拌湿喷混凝土可压送性的主要因素为流动性。（3）提出了高含气量湿喷混凝土引气剂类型优选方法，揭示了组成材料对高含气量湿喷混凝土工作性的影响规律。结果表明，掺量为0.02%AES引气剂与掺量为0.5%聚羧酸减水剂复合配制的新拌混凝土含气量达18%左右，流动性大、稳定性好，喷射后新拌湿喷混凝土含气量降至6%以下，不掺速凝剂的一次喷射厚度达170mm以上，解决了湿喷混凝土可压送性与可喷性难以统一的矛盾。（4）利用直剪法试验，借助XRD图谱，采用正交设计方法分析了组成材料对新拌混凝土内聚力的影响规律，得出了影响新拌混凝土内聚力的主次因素及排序结果。根据材料力学横力弯曲理论，建立了一次喷射厚度力学模型，分析了一次喷射厚度的受力特点，确立了一次喷射厚度与湿喷混凝土内聚力的关系，验证了力学模型的有效性。（5）剖析了混凝土稠度、工作风压、喷射厚度、组成材料对回弹率的影响规律，基于Armelin建立的干喷混凝土的回弹判定准则，探析了湿喷混凝土的回弹机理。结果表明：工作风压存在理想值；回弹率随混凝土流动性降低有增大趋势，随喷射厚度增大逐渐降低，达50mm时，趋于稳定；高含气量湿喷混凝土较普通湿喷混凝土回弹率降低约5%左右，掺入粉煤灰可改善湿喷混凝土的可喷性。（6）对比了高含气量湿喷混凝土与普通湿喷混凝土喷射后的抗压强度及抗冻性能，研究了湿喷混凝土水化物的SEM形貌与强度生长机理，分析了组成材料对强度与抗冻性的影响。结果表明，高含气量湿喷混凝土喷射后28d抗压强度达34.4MPa，，满足设计强度C25要求，抗冻等级满足F300技术要求。（7）利用计算法、简易试验法综合确定混合骨料紧装堆积空隙体积，基于Dennis等建立的管径与润滑层厚度关系计算润滑层体积，由混合骨料紧装堆积空隙体积和润滑层体积确定最小胶浆体积，提出了高含气量湿喷混凝土组成设计方法，并在隧洞的斜井与仰坡工程中进行了应用，对1m3湿喷混凝土的经济成本对比分析表明，高含气量湿喷混凝土具有明显的价格优势。
[Abstract]:As the wet shotcrete has the advantages of improving the construction work environment, facilitating the production and quality control of the concrete, and being beneficial to the development of the advantages of high-performance sprayed concrete and the like, the wet shotcrete has the advantages of difficult coordination of pressure delivery and sprayability, no rule-based design, poor pressure delivery, The defects of small injection thickness, high rebound rate and large amount of liquid accelerator have greatly restricted its wide application in infrastructure construction today. In this paper, the working properties and hardening characteristics of ordinary wet shotcrete and high gas content wet shotcrete are studied systematically, and the following work is done mainly: (1) Optimizing the performance evaluation of one-time injection thickness and rebound rate of new wet shotcrete In this paper, the consistency of wet shotcrete is characterized by the penetration of the vertebral body into the new mixed concrete, and the new method is used to test the new wet shotcrete. Methods: (2) The wet spraying machine was used as the evaluation index for the pressure delivery of the ordinary wet shotcrete, and the relative pressure and the water yield of S10 to 40% were used as the evaluation index for the pressure delivery of the common wet shotcrete. The results show that the pressure and water ratio of the new wet sprayed concrete is higher than that of the new wet shotcrete. The preferred method for the type of air entraining agent with high gas content wet shotcrete is put forward, and the wet shotcrete with high content of air is revealed. The results show that the content of the new mixed concrete is about 18%, the fluidity is large, the stability is good, the air content of the newly mixed wet shotcrete after injection is reduced to below 6%, and the thickness of the non-mixing accelerator is less than 6%. Up to 170mm, the pressure delivery and sprayability of wet shotcrete are solved. It is difficult to unify the contradiction. (4) By means of the direct shear test, by means of the XRD pattern, the influence law of the composition material on the new mixed concrete is analyzed by means of the orthogonal design method, and the influence on the cohesion of the new mixed concrete is obtained. Based on the theory of transverse force bending of material mechanics, a mechanical model of injection thickness is established, the stress characteristics of primary injection thickness are analyzed, and the relationship between primary injection thickness and wet shotcrete is established. The effectiveness of mechanics model was validated. (5) The effect of concrete consistency, working air pressure, spray thickness, composition material on rebound rate was analyzed, and the criterion of rebound determination of dry-sprayed concrete based on Armelin was analyzed. In this paper, the springback mechanism of wet shotcrete is discussed. The results show that the ideal value exists in the working air pressure, the rebound rate decreases with the decrease of the fluidity of the concrete, decreases with the increase of the injection thickness, and tends to be stable when it reaches 50mm. The high gas content wet shotcrete is more common. The rebound rate of shotcrete is reduced by about 5%, and the mixed powder Coal ash can improve the sprayability of wet shotcrete. (6) Compared with the compressive strength and frost resistance of wet shotcrete and ordinary wet shotcrete, the SEM morphology and strength growth mechanism of wet shotcrete are studied. The effect of composition materials on strength and frost resistance was analyzed. The results showed that the compressive strength of 28d after injection of wet shotcrete with high content of air was 34.4MPa, and the design strength was satisfied. According to the requirements of F300 technical requirements, the frost resistance level meets the technical requirements of F300. (7) By means of the calculation method, the simple test method comprehensively determines the void volume of the mixed aggregate, calculates the volume of the lubricating layer based on the relationship between the pipe diameter established by Dennis and the like and the thickness relation of the lubricating layer, and is tightly packed by the mixed aggregate. The volume of void volume and the volume of lubricating layer are determined, and the design method of high gas content wet shotcrete is put forward, and the economic cost contrast analysis table of 1m3 wet shotcrete is applied in inclined shaft and inverted slope engineering of tunnel.
【学位授予单位】：长安大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U414

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