硝酸侵蚀喷射混凝土耐久性能试验研究

发布时间：2018-11-26 10:28

【摘要】：汽车尾气排放量日益增多,尾气中氮氧化物氧化为硝酸。对隧道衬砌混凝土结构,尤其对喷射混凝土单层永久衬砌结构耐久性能产生一定影响。本文开展硝酸侵蚀喷射混凝土试验,研究尾气中氮氧化物对喷射混凝土耐久性能的影响。本文对喷射混凝土进行硝酸溶液长期浸泡试验,从微观、介观、宏观三个层面研究硝酸侵蚀喷射混凝土性能劣化规律及机理。采用X射线衍射法、扫描电镜法对不同侵蚀时间、不同p H值下喷射混凝土矿物成分、微观形貌进行了分析,从微观角度解释了硝酸侵蚀过程,揭示了硝酸对喷射混凝土的侵蚀机理和微观结构变化规律。试验测试了侵蚀后喷射混凝土孔溶液碱度和硝酸根质量百分数,分析了浸泡时间和p H值对喷射混凝土碱度和硝酸根质量百分数的影响,得出了侵蚀后喷射混凝土碱度变化规律和硝酸根迁移机理。研究了浸泡时间、浸泡溶液p H值、钢纤维掺量对喷射混凝土质量损失率、抗压强度、劈裂抗拉强度、损伤层厚度、相对动弹性模量的影响规律,建立了混凝土相对动弹性模量与抗压强度、劈裂抗拉强度、损伤层厚度的计算模型。引入钢纤维影响系数,研究了钢纤维喷射混凝土抗压强度、劈裂抗拉强度、损伤层厚度经时变化过程及规律。通过分析硝酸侵蚀后同配合比普通混凝土和喷射混凝土试件基本性能变化规律,研究了两者在硝酸侵蚀过程中破坏机理的差异性及其对耐久性能的影响。
[Abstract]:The emission of automobile exhaust is increasing day by day, the nitrogen oxide in the tail gas is oxidized to nitric acid. It affects the durability of tunnel lining concrete structure, especially shotcrete monolayer permanent lining structure. The effect of nitrogen oxides in tail gas on durability of shotcrete was studied in this paper. In this paper, the long-term immersion test of nitric acid solution for shotcrete is carried out, and the deterioration law and mechanism of nitric acid erosive shotcrete are studied from three aspects: microscopic, mesoscopic and macroscopic. The mineral composition and morphology of shotcrete at different erosion times and pH values were analyzed by means of X-ray diffraction and scanning electron microscopy, and the process of nitric acid erosion was explained from the microscopic point of view. The erosion mechanism and microstructure of shotcrete caused by nitric acid are revealed. The alkalinity and nitrate mass percentage of shotcrete pore solution after erosion were tested, and the effects of soaking time and pH value on basicity and nitrate mass percentage of shotcrete were analyzed. The alkalinity of shotcrete after erosion and the mechanism of nitrate migration are obtained. The effects of immersion time, pH value of soaking solution and steel fiber content on mass loss rate, compressive strength, splitting tensile strength, thickness of damage layer and relative dynamic elastic modulus of shotcrete were studied. The calculation models of relative dynamic modulus of elasticity, compressive strength, splitting tensile strength and thickness of damage layer of concrete are established. The influence coefficient of steel fiber is introduced to study the changing process and law of compressive strength, splitting tensile strength and thickness of damage layer of steel fiber sprayed concrete. Based on the analysis of the basic properties of concrete and shotcrete specimens after nitric acid erosion, the difference of failure mechanism between them and their effects on durability were studied.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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