本文選題：鋼筋混凝土 + 點(diǎn)蝕　； 參考：《華中科技大學(xué)》2014年博士論文

【摘要】：鋼筋混凝土結(jié)構(gòu)受氯鹽、CO2、SO42-、氧含量、溫濕度、混凝土微觀結(jié)構(gòu)和施工缺陷等多方面影響,導(dǎo)致混凝土綜合性能劣化,進(jìn)而造成鋼筋表面發(fā)生局部或者全面腐蝕。而銹蝕層的發(fā)展又會(huì)引起混凝土層脹裂,導(dǎo)致結(jié)構(gòu)的強(qiáng)度受損,使服役壽命降低。 由于混凝土為高堿性環(huán)境,鋼筋表面往往優(yōu)先發(fā)生以點(diǎn)蝕為代表的局部腐蝕。盡管工程上為延緩鋼筋銹蝕時(shí)間,常在新拌混凝土內(nèi)加入鋼筋阻銹劑,但阻銹劑對(duì)混凝土下鋼筋點(diǎn)蝕的抑制機(jī)理目前尚無定論。特別是采用常規(guī)電化學(xué)方法難以獲取混凝土覆蓋層下鋼筋局部腐蝕的萌發(fā)、生長(zhǎng)或阻銹劑修復(fù)等細(xì)節(jié)。本文以阻銹劑在混凝土中的擴(kuò)散以及對(duì)鋼筋點(diǎn)蝕的抑制機(jī)理為研究重點(diǎn),取得了如下認(rèn)識(shí)： 1)以絲束電極(WBE)技術(shù)研究了混凝土下鋼筋穩(wěn)態(tài)及亞穩(wěn)態(tài)點(diǎn)蝕的演變過程,模擬了侵蝕性粒子與阻銹劑在鋼筋/混凝土界面層內(nèi)的遷移、競(jìng)爭(zhēng)吸附行為。研究了烯胺類,醇胺類與無機(jī)型亞硝基阻銹劑在模擬孔隙液內(nèi)和混凝土內(nèi)對(duì)碳鋼點(diǎn)蝕的抑制機(jī)理,發(fā)現(xiàn)二甲基乙醇胺(DMEA)在混凝土中的遷移效率高于三乙烯四胺(TETA),但對(duì)鋼筋點(diǎn)蝕的抑制作用不及TETA顯著。此外,有機(jī)型阻銹劑對(duì)銹層覆蓋下的點(diǎn)蝕修復(fù)存在明顯滯后,反而會(huì)在一定時(shí)間內(nèi)加劇腐蝕的不均勻性。通過WBE表面陽(yáng)極電流的統(tǒng)計(jì)分析,建立了局部腐蝕因子(LF),實(shí)現(xiàn)了腐蝕不均勻程度以及阻銹劑對(duì)局部腐蝕修復(fù)能力的定量表征。 2)干濕循環(huán)加速實(shí)驗(yàn)表明：在干周期內(nèi),氧在混凝土微孔內(nèi)擴(kuò)散迅速,并將先期形成的腐蝕產(chǎn)物如FeO和Fe304氧化為FeOOH,而在濕周期,陽(yáng)極釋放的電子將其再還原為Fe(Ⅱ),即銹蝕產(chǎn)物在缺氧條件下代替O2參與了腐蝕的陰極去極化過程,使腐蝕過程得以延續(xù)。 3)借助3D顯微鏡、電化學(xué)噪聲(ECN)、電化學(xué)阻抗和激光拉曼等方法,研究了模擬孔隙液中鋼筋表面亞穩(wěn)態(tài)蝕點(diǎn)誘發(fā)、生長(zhǎng)或死亡的動(dòng)態(tài)過程,探討了腐蝕產(chǎn)物對(duì)亞穩(wěn)態(tài)向穩(wěn)態(tài)蝕點(diǎn)轉(zhuǎn)變的催化機(jī)理,原位監(jiān)測(cè)了阻銹劑分子對(duì)亞穩(wěn)態(tài)蝕點(diǎn)的阻滯過程,發(fā)現(xiàn)亞穩(wěn)態(tài)蝕點(diǎn)產(chǎn)生的電流峰幅值及壽命可反映鈍化膜的破裂與修復(fù)難易程度,基于噪聲峰數(shù)值模擬,用鈍化膜電容充放電模型解釋了亞穩(wěn)態(tài)點(diǎn)蝕電流與電位峰快速上升／緩慢衰減的成因,發(fā)展了鋼筋銹蝕產(chǎn)物對(duì)蝕點(diǎn)生長(zhǎng)的促進(jìn)模型。 4)通過SEM. XPS、AFM、ECN和Mott-Schottky圖,研究了阻銹劑分子在裸鋼和銹蝕產(chǎn)物表面的吸附行為差異。發(fā)現(xiàn)N02-與TEPA均能降低碳鋼鈍化膜中的載流子濃度,提高鈍化膜的抗C1-侵蝕能力。TEPA傾向以鈍化膜中氧空位為吸附中心,預(yù)膜條件下可增強(qiáng)鋼筋的抗點(diǎn)蝕能力,但難以抑制銹層覆蓋下的點(diǎn)蝕發(fā)展。NO2-離子在混凝土中擴(kuò)散速率低于有機(jī)胺,但它能更快突破腐蝕產(chǎn)物,相比有機(jī)胺,表現(xiàn)出對(duì)穩(wěn)態(tài)點(diǎn)蝕的快速抑制能力。XPS表明：TETA在金屬基體表面存在鍵合作用,Nls峰顯示出明顯的化學(xué)位移,因而表現(xiàn)出較好的阻銹作用；但在銹蝕層表面,N難以與Fe3+形成有效鍵合,因而難以抑制銹蝕層下的蝕點(diǎn)發(fā)展。
[Abstract]:Reinforced concrete structures are affected by chloride, CO2, SO42-, oxygen content, temperature and humidity, concrete microstructure and construction defects, which lead to the deterioration of the comprehensive performance of concrete, which will cause local or comprehensive corrosion on the surface of the steel bar, and the development of the corrosion layer will cause the swelling of the concrete layer, which leads to the damage of the structure strength and the service life. Life is reduced.
Because the concrete is high alkaline environment, the surface of steel bar often takes precedence of local corrosion represented by pitting corrosion. Although the steel corrosion inhibitor is often added to the fresh concrete in order to postpone the corrosion time of the reinforced bar, the inhibition mechanism of corrosion inhibitor on the pitting corrosion of the reinforced concrete under concrete is not yet conclusive. In order to obtain the details of local corrosion of steel bar under concrete covering layer, growth or rust inhibitor repair, this paper focuses on the diffusion of rust inhibitor in concrete and the inhibition mechanism of pitting corrosion of steel bar.
1) the evolution process of steady and metastable pitting of steel bar under concrete was studied by WBE technique. The migration of corrosive particles and rust inhibitor in the interface layer of reinforced concrete was simulated, and the behavior of competitive adsorption was simulated. The carbon steel points in the simulated pore fluid and in the concrete were studied in the simulated pore fluid and the concrete. The inhibition mechanism of corrosion was found that the transfer efficiency of two methyl ethanolamine (DMEA) in concrete was higher than that of three ethylene four amine (TETA), but the inhibition effect on pitting corrosion was not as significant as that of TETA. In addition, there was a significant lag in the repair of pitting corrosion under the rust layer covering the rust layer, and it would increase the inhomogeneity of corrosion in a certain time. Through WBE The local corrosion factor (LF) was established by the statistical analysis of the surface anode current. The uneven corrosion degree and the quantitative characterization of the corrosion resistance of the corrosion inhibitor to the local corrosion repair were realized.
2) the dry and wet cycle accelerated experiments showed that in the dry cycle, oxygen diffused rapidly in the concrete micropores and oxidized the corrosion products such as FeO and Fe304 to FeOOH, while in the wet cycle, the electrons released by the anode reduced them to Fe (II), that is, the corrosion products took part in the corrosion cathodic depolarization process instead of O2 under the condition of hypoxia. The corrosion process continues.
3) by means of 3D microscope, electrochemical noise (ECN), electrochemical impedance and laser Raman, the dynamic process of metastable corrosion point induced, growth or death in the simulated pore fluid is studied. The catalytic mechanism of the metastable corrosion point transition of the corrosion product to metastable steady corrosion point is discussed, and the resistance of the inhibitor to metastable corrosion point is monitored in situ. It is found that the amplitude and life of the current peak produced by the metastable corrosion point can reflect the failure and repair of the passivation film. Based on the numerical simulation of the noise peak, the cause of the rapid rise / slow decay of the metastable pitting current and the potential peak is explained by the passive film capacitance charge discharge model, and the corrosion products of the steel bar are developed to the corrosion point. Promote the model.
4) through the SEM. XPS, AFM, ECN and Mott-Schottky diagrams, the difference of adsorption behavior between the rust inhibitor on the surface of bare steel and corrosion product was studied. It was found that both N02- and TEPA could reduce the carrier concentration in the passivation film of carbon steel and improve the anti C1- erosion ability of the passivation film with the oxygen vacancy in the passivation film as the adsorption center and the pre film conditions could be enhanced. The anti pitting ability of the steel bar is difficult to suppress the pitting corrosion under the rust layer. The diffusion rate of.NO2- ions in the concrete is lower than that of the organic amine, but it can break through the corrosion products faster. Compared with the organic amine, the rapid inhibition ability of the stable pitting.XPS shows that there is a bonding effect of TETA on the surface of the metal matrix, and the Nls peak shows obvious. The chemical displacement shows good corrosion resistance, but on the surface of the corrosion layer, N is difficult to form an effective bond with Fe3+, so it is difficult to inhibit the development of corrosion point under the rust layer.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU375

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本文編號(hào)：2008181