干旱风沙地区混凝土结构裂缝控制技术研究与应用

发布时间：2018-04-29 15:10

本文选题：干旱风沙 + 混凝土　；参考：《中国铁道科学研究院》2015年博士论文

【摘要】：针对西部地区大风干旱大温差的环境条件造成混凝土养护困难且极易开裂的现状。采用理论分析、室内微观和宏观性能测试以及现场工程验证相结合的研究方法,研发出与干旱风沙地区环境相适应的混凝土抗裂材料,提出了混凝土裂缝控制的成套技术,为促进西部地区混凝土抗裂技术的发展和应用提供了重要的参考。所开展的工作和取得的成果有：首先,调研现场环境条件和混凝土结构开裂特征,分析干旱风沙地区混凝土裂纹发生规律及机理,明确水分蒸发快和收缩大是材料层面造成混凝土开裂的主要因素。从工程实际对混凝土技术性和经济性需求角度出发,提出内部补偿湿度和外部减少蒸发的混凝土裂缝控制技术思路。其次,采用不同的合成工艺制备出不同种类的高吸水树脂(SAP),通过在不同介质、不同离子强度溶液中的吸水倍率、吸水速率试验以及对混凝土拌合物性能、变形性能的影响,优选出丙烯酰胺类高吸水树脂作为湿度调控组分,并确定其粒径大小为0.12mm～ 0.25mm。优选出保水组分和减缩组分与湿度调控组分匹配化设计,开发出具有12h减缩率为56%、28d减缩率为25%,显著提高混凝土的抗裂性能且不降低混凝土强度和耐久性的内养护材料。再次,针对干旱风沙地区常规的浇水覆盖保湿养护较难实现,且不能解决混凝土的早期水份散失问题,系统研究了成膜组分、无机增强组分和改性组分对混凝土养护剂保水性能的影响规律,结合干旱风沙地区环境特征,开发出性能良好,有效保水率达85%以上外养护剂,提出了适合于现场应用的养护剂性能评价方法及混凝土养护效果优劣的评价指标。然后,在研究辅助胶凝材料及配合比配制参数对混凝土工作性能、力学性能、体积稳定性能和耐久性能的影响规律的基础上,提出了遵循“三低一高”(低胶材用量、低用水量、低坍落度、高含气量)原则,并通过补偿化学收缩理论计算及试配验证掺入适量的SAP引入内养护水的高抗裂内养护混凝土配制技术。采用XRD、TG、孔结构分析与核磁共振测试技术分析了水泥浆体中各相水的分布,研究了内养护水对体系毛细负压、水化程度及孔结构的影响规律,提出了吸蓄水SAP在水泥浆体水化过程中的作用模型,揭示了内养护作用机制。最后,系统研究了高抗裂内养护混凝土的搅拌、运输、浇注、振捣和养护工艺等工程应用的关键技术,将研发的具有减缩抗裂作用的内养护材料和具有高效保水作用的外养护剂应用于兰新铁路第二双线混凝土工程,实现了干旱风沙地区混凝土结构裂缝宽度满足规范验收要求的目的,弥补了现有混凝土抗裂技术与环境适应性差、对养护依赖性强和作用对象单一等不足。
[Abstract]:In view of the environmental condition of high temperature difference caused by high wind and drought in the western region, the maintenance of concrete is difficult and it is easy to crack. By means of theoretical analysis, indoor microscopic and macroscopic performance testing and field engineering verification, a concrete crack resistant material adapted to the environment of arid wind-sand area was developed, and a complete set of concrete crack control technology was put forward. It provides an important reference for the development and application of concrete crack resistance technology in the western region. The main works and achievements are as follows: first of all, by investigating the environmental conditions and cracking characteristics of concrete structures, we analyze the occurrence law and mechanism of concrete cracks in arid wind-sand areas. It is clear that fast moisture evaporation and large shrinkage are the main factors causing concrete cracking. From the point of view of the technical and economic requirements of concrete in engineering practice, this paper puts forward the technical thinking of concrete crack control with internal humidity compensation and external evaporation reduction. Secondly, different kinds of superabsorbent resin (SAP) were prepared by different synthetic processes. The effects of water absorption ratio, water absorption rate test and the effect on concrete mixing properties and deformation properties in different medium and different ionic strength solution were studied. Acrylamide superabsorbent resin was selected as humidity control component and its particle size was determined to be 0.12mm ~ 0.25mm. An internal curing material with 12h shrinkage reduction rate of 56 and 28 days is developed, which can significantly improve the crack resistance of concrete and does not reduce the strength and durability of concrete. Thirdly, in view of the difficulty of water mulching and moisturizing maintenance in arid wind-sand area and the failure to solve the problem of water loss in early stage of concrete, the film-forming components are studied systematically. The effect of inorganic reinforcement and modified components on the water retention performance of concrete curing agents was studied. Combined with the environmental characteristics of arid wind-sand areas, a good performance was developed, and the effective water retention rate was more than 85%. The performance evaluation method of curing agent suitable for field application and the evaluation index of curing effect of concrete are put forward. Then, on the basis of studying the influence of auxiliary cementing materials and mixing ratio parameters on the performance, mechanical properties, volume stability and durability of concrete, it is proposed to follow the principle of "three low and one high" (low rubber content). The principle of low water consumption, low slump and high gas content is used. The compounding technology of high crack curing concrete with proper amount of SAP is verified by the calculation of compensatory chemical shrinkage theory and the trial match. The distribution of water in different phases of cement paste was analyzed by means of XRDX TG, pore structure analysis and nuclear magnetic resonance (NMR) technique. The effects of internal curing water on the capillary negative pressure, hydration degree and pore structure of the cement paste were studied. The action model of SAP in hydration of cement paste is proposed, and the mechanism of internal curing is revealed. Finally, the key technologies of mixing, transporting, pouring, vibrating and curing technology of high crack resistant inner curing concrete are systematically studied. The developed internal curing materials with shrinkage and crack resistance and external curing agents with high efficiency and water retention were applied to the second double-track concrete project of Lanxin Railway. The crack width of concrete structure in arid wind-sand area can meet the requirements of code acceptance, which makes up for the shortcomings of existing concrete crack resistance technology and environmental adaptability, strong dependence on conservation and single object of action and so on.
【学位授予单位】：中国铁道科学研究院
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU755.7

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