干濕循環(huán)作用下混凝土中氯離子傳輸性能及臨界濃度研究
發(fā)布時間：2018-09-11 16:51
【摘要】：海洋環(huán)境中浪濺區(qū)與潮汐區(qū)是鋼筋混凝土結(jié)構(gòu)耐久性破壞最為嚴(yán)重的兩個區(qū)域，由此導(dǎo)致的鋼筋混凝土結(jié)構(gòu)耐久性失效問題給整個社會帶來諸多安全隱患和巨額經(jīng)濟損失。因此，正確認(rèn)識其腐蝕行為成為耐久性研究的重要課題之一。 本文根據(jù)浪濺區(qū)與潮汐區(qū)鋼筋混凝土結(jié)構(gòu)的腐蝕機理，，研究了干濕循環(huán)作用下混凝土中氯離子的傳輸規(guī)律，探討了混凝土中鋼筋腐蝕臨界點的監(jiān)測與判斷方法，分析了混凝土中鋼筋腐蝕的臨界氯離子濃度，最后對鋼筋混凝土結(jié)構(gòu)耐久性壽命進行預(yù)測分析。研究成果將為海洋腐蝕環(huán)境中鋼筋混凝土結(jié)構(gòu)的鋼筋銹蝕診斷及耐久性壽命預(yù)測提供理論依據(jù)。具體內(nèi)容如下： 論文采用化學(xué)滴定法和氯離子選擇電極法對標(biāo)準(zhǔn)濃度NaCl溶液進行對比測試試驗，結(jié)果表明了氯離子選擇電極法比化學(xué)滴定法的測試精度高；綜合利用交流阻抗譜法、線性極化法和Tafel極化法對混凝土中鋼筋開始腐蝕臨界點進行了監(jiān)測試驗，測試結(jié)果及擬合分析表明此方法可以對混凝土中鋼筋腐蝕的臨界時間點進行有效監(jiān)測。 開展了不同干濕循環(huán)時間比例對混凝土中氯離子傳輸性能影響的試驗研究，結(jié)果表明：不同干濕循環(huán)時間比例作用下對流區(qū)深度均在2mm左右；對流區(qū)深度Δx處的氯離子濃度值Cs,Δx與干燥時間存在線性關(guān)系，隨干燥時間的增加而降低，但降低幅度較小；氯離子擴散系數(shù)與干濕時間比值之間存在明顯線性相關(guān)性，隨干濕時間比值的增加而增大。 通過交流阻抗譜法等鋼筋銹蝕檢測技術(shù)研究了鋼筋腐蝕的臨界氯離子濃度，分析了干濕循環(huán)時間比例、循環(huán)周期、粉煤灰摻量對臨界氯離子濃度的影響。試驗結(jié)果表明：臨界氯離子濃度與試件干燥過程結(jié)束時飽和度之間有明顯的線性相關(guān)性，隨著試件干燥過程結(jié)束時飽和度的增大而減少；臨界氯離子濃度值隨著干濕循環(huán)周期的增大，基本呈增大趨勢；臨界氯離子濃度隨粉煤灰摻量的增加先增大后減少，說明粉煤灰雖然可以增加混凝土的密實性，但也降低混凝土孔溶液的pH值，因此其抗氯離子侵蝕能力隨著粉煤灰摻量的增加先增強后下降。 在上述研究基礎(chǔ)上，對干濕循環(huán)作用混凝土結(jié)構(gòu)的耐久性壽命進行了預(yù)測，結(jié)果表明此區(qū)域混凝土結(jié)構(gòu)的使用年限一般為10~20年，遠達不到設(shè)計要求，因此應(yīng)采取必要的耐久性設(shè)計及防護措施。
[Abstract]:In the marine environment, the wave splash area and the tidal zone are the two regions where the durability of reinforced concrete structures is most seriously damaged. The durability failure of reinforced concrete structures has brought a lot of safety risks and huge economic losses to the whole society. Therefore, the correct understanding of its corrosion behavior has become an important subject of durability research. According to the corrosion mechanism of reinforced concrete structures in the splash zone and tidal zone, this paper studies the law of chloride transfer in concrete under the action of dry-wet cycle, and discusses the monitoring and judging method of the critical point of reinforcement corrosion in concrete. The critical chloride concentration of reinforced concrete corrosion is analyzed. Finally, the durability life of reinforced concrete structure is predicted and analyzed. The research results will provide theoretical basis for corrosion diagnosis and durability life prediction of reinforced concrete structures in marine corrosion environment. The main contents are as follows: chemical titration method and chloride ion selective electrode method are used to test the standard concentration of NaCl solution. The results show that the chloride ion selective electrode method is more accurate than the chemical titration method. Based on AC impedance spectrum method, linear polarization method and Tafel polarization method, the critical corrosion point of steel bars in concrete is monitored and tested. The test results and fitting analysis show that this method can effectively monitor the critical time point of steel bar corrosion in concrete. The effect of different dry and wet cycle time ratio on chloride transport performance in concrete was studied. The results showed that the depth of convective zone was about 2mm under different dry and wet cycle time ratio. The chloride concentration value Cs, 螖 x at the depth of convection zone 螖 x has a linear relationship with the drying time and decreases with the increase of drying time, but the decrease is small, and there is a significant linear correlation between the chloride diffusion coefficient and the ratio of dry and wet time. With the increase of the ratio of dry and wet time, it increases. The critical chloride ion concentration of steel bar corrosion was studied by means of AC impedance spectroscopy and other techniques. The effects of dry and wet cycle time ratio cycle period and fly ash content on critical chlorine ion concentration were analyzed. The experimental results show that there is a significant linear correlation between the critical chlorine concentration and the saturation at the end of the drying process, which decreases with the increase of the saturation at the end of the drying process. With the increase of dry and wet cycle, the critical chlorine ion concentration increases first and then decreases with the increase of fly ash content, which indicates that fly ash can increase the compactness of concrete. However, the pH value of concrete pore solution is also reduced, so its resistance to chloride ion corrosion increases first and then decreases with the increase of fly ash content. On the basis of the above research, the durability life of concrete structures subjected to dry-wet cycling is predicted. The results show that the service life of concrete structures in this area is generally 10 ~ 20 years, which is far from the design requirements. Therefore, the necessary durability design and protective measures should be taken.
【學(xué)位授予單位】：西安建筑科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU528
[Abstract]:In the marine environment, the wave splash area and the tidal zone are the two regions where the durability of reinforced concrete structures is most seriously damaged. The durability failure of reinforced concrete structures has brought a lot of safety risks and huge economic losses to the whole society. Therefore, the correct understanding of its corrosion behavior has become an important subject of durability research. According to the corrosion mechanism of reinforced concrete structures in the splash zone and tidal zone, this paper studies the law of chloride transfer in concrete under the action of dry-wet cycle, and discusses the monitoring and judging method of the critical point of reinforcement corrosion in concrete. The critical chloride concentration of reinforced concrete corrosion is analyzed. Finally, the durability life of reinforced concrete structure is predicted and analyzed. The research results will provide theoretical basis for corrosion diagnosis and durability life prediction of reinforced concrete structures in marine corrosion environment. The main contents are as follows: chemical titration method and chloride ion selective electrode method are used to test the standard concentration of NaCl solution. The results show that the chloride ion selective electrode method is more accurate than the chemical titration method. Based on AC impedance spectrum method, linear polarization method and Tafel polarization method, the critical corrosion point of steel bars in concrete is monitored and tested. The test results and fitting analysis show that this method can effectively monitor the critical time point of steel bar corrosion in concrete. The effect of different dry and wet cycle time ratio on chloride transport performance in concrete was studied. The results showed that the depth of convective zone was about 2mm under different dry and wet cycle time ratio. The chloride concentration value Cs, 螖 x at the depth of convection zone 螖 x has a linear relationship with the drying time and decreases with the increase of drying time, but the decrease is small, and there is a significant linear correlation between the chloride diffusion coefficient and the ratio of dry and wet time. With the increase of the ratio of dry and wet time, it increases. The critical chloride ion concentration of steel bar corrosion was studied by means of AC impedance spectroscopy and other techniques. The effects of dry and wet cycle time ratio cycle period and fly ash content on critical chlorine ion concentration were analyzed. The experimental results show that there is a significant linear correlation between the critical chlorine concentration and the saturation at the end of the drying process, which decreases with the increase of the saturation at the end of the drying process. With the increase of dry and wet cycle, the critical chlorine ion concentration increases first and then decreases with the increase of fly ash content, which indicates that fly ash can increase the compactness of concrete. However, the pH value of concrete pore solution is also reduced, so its resistance to chloride ion corrosion increases first and then decreases with the increase of fly ash content. On the basis of the above research, the durability life of concrete structures subjected to dry-wet cycling is predicted. The results show that the service life of concrete structures in this area is generally 10 ~ 20 years, which is far from the design requirements. Therefore, the necessary durability design and protective measures should be taken.
【學(xué)位授予單位】：西安建筑科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU528
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