氯离子侵蚀环境下PC桥梁碳化模型试验研究

发布时间：2018-05-09 03:16

本文选题：混凝土碳化 + 数值模型　；参考：《长安大学》2017年硕士论文

【摘要】：混凝土碳化带来的结构耐久性问题已经引起了广泛的关注,诸多学者从温度、湿度、水灰比、应力等多角度对混凝土碳化进行了研究,但氯离子侵蚀作为混凝土劣化的重要影响因素,对混凝土碳化的影响研究成果较少,本文以氯离子腐蚀环境为背景条件,研究氯离子侵蚀对混凝土碳化的影响,并建立了混凝土碳化数值模型。为将研究成果从材料层面过渡到工程结构层面,分析讨论应变—孔隙—碳化速率之间的关系,使模型能够适应预应力桥梁等处于应力状态的混凝土结构。分别设计、实施:(1)无应力状态的混凝土纯碳化试验(CO2);(2)无应力状态的混凝土在氯盐侵蚀下的碳化试验(Cl~-+CO_2);(3)模拟预应力桥梁应力状态的混凝土在氯盐侵蚀下的碳化试验(模拟力+Cl~-+CO_2);(4)轴压应力状态的混凝土在氯盐侵蚀下的碳化试验(轴压力+Cl~-+CO_2);(5)纯弯应力状态和氯盐侵蚀下的混凝土碳化试验(CO2+Cl-+纯弯)。对模型进行验证,证明碳化数值模型的可靠性。此外,结合碳化数值模型解分析碳化试验数据发现:在本试验条件下,相比无氯盐侵蚀的C40、C50混凝土小试块,氯盐侵蚀可降低56%~60%的混凝土碳化速率;氯盐环境下,混凝土与应力的规律关系依然存在,即混凝土处于压应力状态时,其碳化速率显著减小,当处于拉应力状态时,碳化速率明显提高;判断应用轴压混凝土的应力状态等效预应力混凝土结构的应力状态进行碳化研究是可行的,与之相类似的应用纯弯段混凝土外缘的应力状态替代混凝土的轴拉应力状态进行碳化研究也是可行的;在无氯盐侵蚀环境下,不同水灰比对混凝土碳化速率的敏感性较大,当存在氯盐侵蚀时,不同水灰比对混凝土碳化速率依然有明显影响,但其敏感性比无氯盐侵蚀时明显降低。
[Abstract]:Structural durability caused by concrete carbonization has attracted extensive attention. Many scholars have studied the carbonation of concrete from temperature, humidity, water-cement ratio, stress and so on. However, chloride ion erosion, as an important factor affecting concrete deterioration, has little effect on concrete carbonation. In this paper, the influence of chloride ion erosion on concrete carbonization is studied under the background condition of chloride ion corrosion environment. A numerical model of concrete carbonation is established. In order to transfer the research results from the material level to the engineering structure level, the relationship between strain, porosity and carbonation rate is analyzed and discussed, so that the model can adapt to the prestressed concrete structures such as prestressed bridges. Separate design, Carbonation test of concrete in stress state under chloride erosion; carbonation test of concrete under chloride salt erosion; carbonation test of concrete under chloride erosion under simulated stress state of prestressed bridge (simulated force) The carbonation test of concrete under chloride erosion (axial pressure Cl-CO2C / C) under axial compression stress state and concrete carbonization test under chloride corrosion is carried out in the case of pure bending stress state and carbonization test of concrete under chloride corrosion. The model is verified to prove the reliability of the carbonation numerical model. In addition, the carbonation test data are analyzed with the solution of carbonation numerical model. It is found that the carbonation rate of concrete can be reduced by 56% or 60% compared with the C40 C50 concrete sample without chloride erosion under the condition of chloride salt, and the carbonation rate of the concrete can be reduced by 56% under the chloride environment. The relationship between concrete and stress still exists, that is, when the concrete is in the state of compressive stress, the carbonation rate decreases significantly, and when the concrete is in the state of tensile stress, the rate of carbonation increases obviously. It is feasible to use the stress state of axially compressed concrete to study the stress state of prestressed concrete structure. Similarly, it is feasible to apply the stress state of the outer edge of pure curved section concrete to replace the axial tensile stress state of concrete for carbonization, and under the condition of no chlorine salt erosion, the different water-cement ratio is more sensitive to the carbonation rate of concrete. When chloride erosion exists, the carbonation rate of concrete is still affected by different water-cement ratio, but its sensitivity is obviously lower than that without chloride salt erosion.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U446.1

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