發(fā)布時(shí)間：2018-03-17 20:27

  本文選題：氯離子侵蝕　切入點(diǎn)：碳化氯鹽耦合　出處：《南京工業(yè)大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：鋼筋混凝土是地鐵工程主要的結(jié)構(gòu)材料,鋼筋銹蝕是導(dǎo)致結(jié)構(gòu)過早破壞、結(jié)構(gòu)失效的最主要因素。為了更好地吻合地鐵工程實(shí)際服役條件,非常有必要開展碳化-氯鹽雙重因素同步耦合研究,從而建立更加準(zhǔn)確的地鐵隧道混凝土服役性能演化的分析理論框架,為地鐵結(jié)構(gòu)服役性能評估和修復(fù)提供基礎(chǔ)理論。本文總結(jié)分析國內(nèi)外混凝土氯離子傳輸?shù)睦碚撃Ｐ?采用菲克第二定律作為描述氯離子數(shù)值模型的控制方程。并通過對混凝土碳化反應(yīng)機(jī)理的分析,得出碳化反應(yīng)對氯離子侵蝕過程的主要影響。主要研究內(nèi)容如下：(1)通過對氯離子傳輸機(jī)理的研究,梳理了經(jīng)典傳輸模型及其缺陷。同時(shí),分析已有氯離子侵蝕模型的建立過程,提出了考慮氯離子結(jié)合能力、時(shí)間依賴性、濕度及溫度等多種影響因素耦合作用下的氯離子傳輸理論模型,列出了不同影響因素對氯離子擴(kuò)散系數(shù)的影響,并給出了表達(dá)式及建議取值,并考慮工程實(shí)際修正了相關(guān)參數(shù)。通過試驗(yàn)數(shù)據(jù)驗(yàn)證了模型的可靠性。(2)開展了碳化鹽霧耦合試驗(yàn)。主要測試各侵蝕齡期混凝土中自由氯離子和總氯離子濃度分布規(guī)律,分析氯離子結(jié)合率的變化規(guī)律,試驗(yàn)結(jié)果表明,自由氯離子和總氯離子含量均隨著侵蝕齡期的增加而增多,但是結(jié)合氯離子的比例發(fā)生明顯變化。并測出了混凝土內(nèi)液相pH值變化趨勢,對耦合效應(yīng)的機(jī)理進(jìn)行了分析。(3)通過對碳化機(jī)理的研究,建立CO2時(shí)空分布模型,得出在標(biāo)準(zhǔn)碳化條件下的C02時(shí)空分布規(guī)律。通過碳化反應(yīng)過程的分析,確定碳化過程對氯離子的兩大作用：化學(xué)作用和物理作用。碳化反應(yīng)使混凝土的pH值降低,而使化學(xué)結(jié)合生成Friedel鹽的結(jié)合氯離子得到釋放。因此,碳化反應(yīng)提高了自由氯離子的含量。碳化反應(yīng)過程中CO2會(huì)和C-S-H凝膠以及Ca(OH)2反應(yīng)生成CaCO3,這會(huì)導(dǎo)致混凝土中孔隙率的降低,從而在物理的角度上阻礙了氯離子向混凝土內(nèi)部的擴(kuò)散。(4)采用有限差分法求解本文提出的擴(kuò)散-反應(yīng)方程,并利用matlab編寫相關(guān)程序。對提出的碳化氯鹽耦合模型進(jìn)行算例分析,研究隨著碳化反應(yīng)進(jìn)行,混凝土中氯離子濃度隨時(shí)間和深度的變化規(guī)律。
[Abstract]:Reinforced concrete is the main structural material in subway engineering, and the corrosion of steel bar is the main factor leading to premature destruction and structural failure. It is very necessary to carry out the research of carbonation and chloride double factor synchronous coupling so as to establish a more accurate theoretical framework for the analysis of the evolution of concrete service performance in subway tunnels. This paper summarizes and analyzes the theoretical models of chloride ion transport in concrete at home and abroad. The second law of Fick is used as the governing equation to describe the numerical model of chloride ion, and the mechanism of carbonation reaction of concrete is analyzed. The main research contents are as follows: (1) through the study of the mechanism of chloride ion transport, the classical transport model and its defects are sorted out. At the same time, the establishment process of the existing chloride ion erosion model is analyzed. A theoretical model of chloride ion transport considering the coupling of chloride binding capacity, time dependence, humidity and temperature is put forward, and the influence of different factors on chloride diffusion coefficient is listed. The expressions and suggested values are given. The reliability of the model is verified by the experimental data. The carbonized salt spray coupling test is carried out. The distribution of free chloride ion and total chloride ion in concrete of different erosion ages is mainly tested. The change of chloride binding rate was analyzed. The results showed that both free chloride ion and total chlorine ion content increased with the increase of erosion age. But the ratio of chloride ion changed obviously, and the change trend of pH value in liquid phase of concrete was measured, and the mechanism of coupling effect was analyzed. Through the study of carbonation mechanism, the spatio-temporal distribution model of CO2 was established. Through the analysis of carbonation reaction process, two major effects of carbonation process on chloride ion are determined: chemical action and physical action. Carbonation reaction reduces the pH value of concrete. Therefore, the carbonation reaction increases the content of free chloride ions. During the carbonation reaction, CO2 reacts with C-S-H gel and Ca(OH)2 to form CaCO3, which leads to the decrease of porosity in concrete. Therefore, the diffusion of chloride ions into concrete is prevented from the physical point of view. The finite difference method is used to solve the diffusion-reaction equation proposed in this paper, and the relevant program is compiled by matlab. The variation of chloride ion concentration with time and depth in concrete was studied with carbonation reaction.
【學(xué)位授予單位】：南京工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU528

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