硫酸盐侵蚀混凝土耐久性评估方法研究

发布时间：2018-05-17 08:28

本文选题：混凝土 + 硫酸盐侵蚀　；参考：《山东科技大学》2017年硕士论文

【摘要】：混凝土耐久性研究中硫酸盐侵蚀是一个主要问题,混凝土受硫酸盐侵蚀破坏因素复杂、危害性大,是环境侵蚀中最为严重的一种。当混凝土处于溶有硫酸盐的土壤和地下水中时,硫酸根离子通过扩散作用进入混凝土内部与水泥水化产物发生反应,对混凝土产生膨胀破坏作用,最终导致混凝土结构的性能退化。而位于水位变动区、浪溅区以及潮汐区等部位的混凝土结构遭受干湿循环与硫酸盐的共同作用,混凝土劣化更加严重。因此对于混凝土硫酸盐侵蚀研究应从干湿循环和长期浸泡两方面开展。本论文属于交通运输部建设科技项目《在役混凝土梁桥可靠性检测评估技术体系与装备研发》(2013 318 223 040)中关于“在役混凝土梁桥基于可靠性理论的构件层次耐久性评估方法”的子课题,根据项目专题要求,主要进行了以下工作:(1)通过试验研究了硫酸钠溶液浓度和水灰比对混凝土在硫酸盐干湿循环作用下抗压强度、表面硬度值、质量和动弹性模量等指标变化规律的影响。研究表明随着Na2S04侵蚀溶液浓度的增加,混凝土的各项指标衰减速率越大;随着混凝土水灰比的增大可以延缓混凝土损伤的出现,但最终水灰比大的混凝土受硫酸盐侵蚀破坏程度更大。对比各项指标发现里氏硬度值变化规律比较稳定,可以用来判断混凝土受硫酸盐侵蚀损伤程度。(2)通过对不同硫酸盐浓度干湿循环侵蚀下混凝土试件强度和硬度值的测量分析,建立混凝土里氏硬度表征强度的关系,从而提出基于硬度比对法的硫酸盐侵蚀混凝土耐久性评估方法。该评估方法属于无损检测方法,对现场混凝土结构受硫酸盐侵蚀的检测和耐久性评估具有指导性意义。(3)通过采用硫酸钠溶液长期浸泡的试验方法研究不同水灰比混凝土内硫酸根含量随侵蚀龄期的变化规律。试验结果表明混凝土内硫酸根离子含量随着侵蚀龄期的增加而增大,随着混凝土测试深度的增加而下降,随着混凝土水灰比的减小而降低,表明水灰比低的混凝土抗硫酸盐长期浸泡侵蚀能力更好。(4)通过理论分析混凝土硫酸盐侵蚀反应产物对混凝土造成损伤的过程,提出混凝土受硫酸盐侵蚀开裂临界浓度的定义,给出了硫酸盐侵蚀临界浓度的计算过程。根据硫酸盐侵蚀临界浓度理论计算结果,设计混凝土内掺硫酸钠试验研究混凝土的开裂临界浓度,根据不同掺量硫酸钠混凝土的动弹性模量和抗压强度两项指标的变化规律推断混凝土开裂临界浓度。结果表明试验推测的混凝土受硫酸盐侵蚀的临界开裂浓度与理论分析的临界浓度较为吻合,说明理论分析的正确性,也可以说明内掺硫酸钠的试验方法具有一定的可行性。
[Abstract]:Sulfate erosion is a major problem in the study of concrete durability. It is one of the most serious environmental erosion due to its complex damage factors and great harmfulness. When the concrete is in the soil and groundwater dissolved with sulphate, the sulfate ion enters the concrete through the diffusion action and reacts with the hydration product of the cement, which results in the expansion and destruction of the concrete. Finally, the performance of concrete structure is degraded. However, concrete structures located in the water level changing region, the splash area and the tidal zone are subjected to the combined action of wet and dry circulation and sulfate, so the deterioration of concrete is more serious. Therefore, the study on sulfate erosion of concrete should be carried out from two aspects: wet and dry cycle and long-term soaking. This paper belongs to the Ministry of Communications and Transport construction science and technology project "in service concrete beam bridge reliability testing and evaluation technology system and equipment research and development" in 2013 318,223,040 about "in-service concrete beam bridge based on reliability theory component level durability" Subtopics of the Evaluation method, According to the specific requirements of the project, the following work was mainly carried out: 1) the compressive strength and surface hardness of concrete under the action of sulphate dry and wet cycle were studied by experiments on the concentration of sodium sulfate solution and the ratio of water to cement. The influence of mass and dynamic elastic modulus. The results show that with the increase of the concentration of Na2S04 solution, the attenuation rate of each index of concrete increases, and with the increase of water-cement ratio of concrete, the occurrence of concrete damage can be delayed. But in the end, the concrete with high water cement ratio is more damaged by sulfate erosion. Comparing various indexes, it is found that the law of variation of Richter hardness value is relatively stable, which can be used to judge the damage degree of concrete subjected to sulfate erosion. The strength and hardness of concrete specimens under different sulphate concentrations under dry-wet cyclic erosion are measured and analyzed. The relationship between the hardness of concrete and the strength of concrete is established, and a method for evaluating the durability of sulphate corroded concrete based on hardness comparison method is proposed. The evaluation method belongs to the nondestructive testing method, It is of guiding significance to detect and evaluate the durability of concrete structures subjected to sulfate erosion in the field. (3) by using the method of soaking in sodium sulfate solution for a long time, the variation of sulfate content in concrete with different water / cement ratio with erosion age is studied. The results show that the content of sulfate ion in concrete increases with the increase of erosion age, decreases with the increase of testing depth, and decreases with the decrease of water-cement ratio of concrete. It shows that the concrete with low water-cement ratio has better long-term corrosion resistance to sulfate. (4) through the theoretical analysis of the damage process caused by the sulfate corrosion reaction products of concrete, the definition of critical concentration of concrete cracking by sulfate erosion is put forward. The calculation process of the critical concentration of sulfate erosion is given. According to the theoretical calculation results of sulfate erosion critical concentration, the cracking critical concentration of concrete was studied by experiments with sodium sulfate in concrete. According to the dynamic modulus of elasticity and compressive strength of concrete with different content of sodium sulfate, the crack critical concentration of concrete is deduced. The results show that the critical cracking concentration of the concrete subjected to sulfate erosion is in good agreement with the critical concentration of theoretical analysis, which indicates the correctness of the theoretical analysis and the feasibility of the test method with sodium sulfate in it.
【学位授予单位】：山东科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U444

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