【摘要】：處于海洋、酸雨等環(huán)境下的混凝土結(jié)構(gòu),遭受干濕循環(huán)、硫酸鹽腐蝕等各種環(huán)境因素的侵蝕作用,混凝土的耐久性降低、服役壽命縮短。硫酸鹽侵蝕是引起混凝土耐久性退化的主要因素,而干濕循環(huán)加劇混凝土硫酸鹽腐蝕進(jìn)程,研究硫酸鹽侵蝕和干濕循環(huán)耦合作用下混凝土的耐久性問(wèn)題對(duì)開(kāi)展混凝土結(jié)構(gòu)的長(zhǎng)壽命設(shè)計(jì)、提高工程結(jié)構(gòu)的服役安全性具有重要意義。本文針對(duì)這一問(wèn)題,通過(guò)數(shù)值建模、實(shí)驗(yàn)測(cè)試,研究干濕循環(huán)條件下的水分傳輸、硫酸鹽侵蝕下的離子傳輸與溶液結(jié)晶隨侵蝕時(shí)間的變化規(guī)律。主要內(nèi)容及結(jié)論如下： (1)根據(jù)混凝土中水分傳輸機(jī)制,運(yùn)用Fick定律與Darcy定律,建立了干濕循環(huán)條件下考慮水蒸氣擴(kuò)散和液態(tài)水滲透機(jī)制的混凝土水分傳輸方程,該方程是一個(gè)非線性的偏微分方程,利用單點(diǎn)子域精細(xì)積分法獲得了該方程在一維情況下的半解析解,并應(yīng)用Matlab語(yǔ)言編制了相應(yīng)的分析程序。 (2)設(shè)計(jì)并制作了不同水灰比的水泥砂漿試件,并按水分一維傳輸情況制作了厚度不同的多組切片,以開(kāi)展水分在混凝土中的濕潤(rùn)、干燥和干濕循環(huán)等一維傳輸實(shí)驗(yàn),以驗(yàn)證所建立的水分傳輸模型的合理性。結(jié)果表明,水分傳輸模型的計(jì)算值與實(shí)驗(yàn)測(cè)試值結(jié)果較為一致,說(shuō)明本文所建立的模型可用于分析混凝土中的水分傳輸規(guī)律。 (3)建立了混凝土中水分傳輸?shù)亩S分析方程,利用單點(diǎn)子域精細(xì)積分法獲得了該方程的半解析解,分析了混凝土棱柱體在濕潤(rùn)、干燥和干濕循環(huán)等各種工況下的水分傳輸規(guī)律。結(jié)果表明,混凝土中水分傳輸速率沿試件表面向內(nèi)呈遞減關(guān)系,且在柱截面對(duì)角線上的水分傳輸率較大。 (4)根據(jù)混凝土中硫酸鹽溶液的對(duì)流傳輸過(guò)程,建立了干濕循環(huán)條件下硫酸根離子在混凝土中的傳輸模型,模擬了混凝土中水分蒸發(fā)后硫酸根離子濃度和硫酸鹽結(jié)晶量隨循環(huán)次數(shù)的變化規(guī)律。結(jié)果表明,混凝土試件表層受干濕條件影響最大,其硫酸根離子濃度隨循環(huán)次數(shù)的增加而累積；干燥與濕潤(rùn)時(shí)間對(duì)混凝土內(nèi)硫酸根離子分布的影響很大；混凝土中硫酸鹽的結(jié)晶量隨干濕循環(huán)次數(shù)的增加而逐漸增加。
[Abstract]:Under the environment of ocean and acid rain, the concrete structure is corroded by various environmental factors, such as dry and wet cycle, sulphate corrosion, etc., the durability of concrete is reduced and the service life is shortened. Sulfate erosion is the main factor that causes the degradation of concrete durability, while the drying and wet cycle exacerbates the process of sulphate corrosion of concrete. It is of great significance to study the durability of concrete under the coupling of sulfate erosion and dry-wet cycle to develop the long-life design of concrete structure and improve the service safety of engineering structure. In order to solve this problem, through numerical modeling and experimental test, the changes of water transport under dry and wet cycle, ion transport and solution crystallization under sulfate erosion with erosion time were studied. The main contents and conclusions are as follows: (1) according to the mechanism of water transport in concrete, using Fick's law and Darcy's law, the water transport equation of concrete considering the mechanism of water vapor diffusion and liquid water permeation is established under the condition of dry and wet circulation. The equation is a nonlinear partial differential equation. The semi-analytical solution of the equation in one-dimensional case is obtained by using the single-point domain precise integration method. The corresponding analysis program is compiled by using Matlab language. (2) cement mortar specimens with different water-cement ratio are designed and made, and multi-group slices with different thickness are made according to the one-dimensional water transport. In order to verify the rationality of the proposed water transport model, one-dimensional experiments such as wetting, drying and dry-wet circulation of moisture in concrete were carried out. The results show that the calculated values of water transport model are in good agreement with the experimental results. This model can be used to analyze the law of water transfer in concrete. (3) A two-dimensional analytical equation of water transport in concrete is established, and the semi-analytical solution of the equation is obtained by using the precise integration method of single point domain. The moisture transfer law of concrete prism under various conditions, such as wetting, drying and drying cycle, is analyzed. The results show that the water transfer rate in concrete is decreasing along the surface of the specimen, and the water transfer rate on the diagonal line of column section is larger. (4) according to the convection transport process of sulfate solution in concrete, The transport model of sulfate ion in concrete under dry and wet cycling conditions was established. The variation of sulfate ion concentration and sulfate crystallization with cycle times after water evaporation in concrete was simulated. The results show that the surface layer of concrete is most affected by dry and wet conditions, and the concentration of sulfate ion accumulates with the increase of cycle times, and the time of drying and wetting has a great effect on the distribution of sulfate ions in concrete. The crystallization of sulfate in concrete increases with the increase of dry and wet cycles.
【學(xué)位授予單位】：南京理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU528

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本文編號(hào)：2189028