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標題: | 考量影響腐蝕電流密度之因素建立長期腐蝕預測模型 Long-Term Corrosion Prediction Model Considering the Factors Influencing Corrosion Current Density |
作者: | Meng-Lin Wu 巫孟霖 |
指導教授: | 廖文正(Wen-Cheng Liao) |
關鍵字: | 腐蝕,氯離子,腐蝕電流密度,法拉第定律,鋼筋重量減少率,重量損失試驗,腐蝕預測模型, Corrosion,Chloride ion,Corrosion current density,Faraday’s Law,Weight loss raios of steel rebars,Weight loss test,Corrosion prediction model, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 現行RC耐震評估規範未針對沿海地區受飛來鹽侵害之結構物老劣化現象進行力學性能之折減,考量其折減所須重要參數為鋼筋有效斷面積折減量,故根據電化學理論可藉由現地量測當下鋼筋腐蝕電流密度值推估其重量減少率,但因無法推估量測當下以前長期腐蝕電流密度之發展,且其中存在諸多問題如電化學理論於RC中之適用性及尚未確認量測儀器、鋼筋號數、腐蝕型態等複雜因子對於腐蝕電流密度之影響,導致對於老劣化RC結構物力學折減之過程受阻。 本研究透過研究群中之裸鋼筋加速腐蝕實驗及混凝土中添加氯鹽加速劣化實驗之後續實驗,來解決目前腐蝕電流密度之相關問題。兩項實驗均在特定齡期取出鋼筋後,以重量損失試驗迴歸分析得各鋼筋合理之真實腐蝕電流密度值為基準,來建立本研究之目標結構物位址之長期腐蝕電流密度預測模型。其中第二項實驗為藉由實驗配置之2種水灰比及4種氯鹽添加量之真實腐蝕電流密度值,在考量量測儀器、鋼筋號數等對於腐蝕電流密度之影響後建立初步預測模型;而第一項實驗則主要考量不同防鏽塗裝、量測儀器、鋼筋號數及腐蝕型態等因子影響下,對於腐蝕電流密度的影響得到修正係數,再進一步對初步預測模型進行修正。 由修正結果顯示,在防鏽塗裝之選擇上應選用紅丹漆,在#3鋼筋中之腐蝕抑制效率約為95%,在#7鋼筋中之腐蝕抑制效率約為75%;在相同腐蝕條件下,鋼筋號數不影響真實腐蝕電流密度值,但會影響真實之重量減少率;在相同腐蝕條件下,量測範圍內之腐蝕區域大小不影響腐蝕區域內鋼筋之真實腐蝕電流密度值;對於腐蝕嚴重之鋼筋建議使用GalvaPulse預測真實腐蝕電流密度,恰開始腐蝕之鋼筋則建議採用GalvaPulse及Gecor 8之腐蝕電流密度平均值預測真實腐蝕電流密度。當長期腐蝕電流密度預測模型建置完成後,即可不經現地量測即預測特定結構齡期下之腐蝕電流密度並推算其重量減少率,再導入耐震模型評估結構體老劣化後之耐震餘裕度及改善措施。 由於在設計實驗時不考慮混凝土表面表面披覆材之保護性,故預測模型建置完成後,可得大部分計算得之重量減少率於齡期60年時超出力學折減模型之適用範圍,故若需將該結果應用於一般RC建物,未來須以位址鄰近目標結構物之結構老劣化為示範例,考量披覆材對預測模型之影響進行修正,以推廣長期腐蝕電流密度預測模型之適用範圍,乃至於將此應用於一般老劣化建物之耐震評估中。 Structures on the coastline aging and deterioration influenced by chlorine salts have not been considered into mechanical property reductions of reinforced concrete seismic evaluation code. Considering the important parameters of mechanical property reductions are steel rebars’ cross-sectional area, weight loss ratio could be estimated by corrosion current densities measured in the field according to electrochemical theory; however, the long-term development of corrosion current density before measuring can not be estimated, as well as some problems including the feasibility of electrochemical theory applied to RC structures, and the complex factors such as measuring instruments, sizes of rebars and corrosion types influencing corrosion current density still exists, therefore the process of mechanical property reductions in deteriorated RC structures was impeded. The research resolved current problems relevant to corrosion current densities through the accelerated corrosion test for bare steel rebars and the accelerated corrosion test by adding NaCl into concrete specimens from our research group. These two experiments took out steel rebars on specific concrete ages, and regarded the real corrosion current density analyzed by regression results of weight loss test as benchmark in order to establish long–term corrosion current density prediction model for the target structure. From the experimental datas of the accelerated corrosion test by adding NaCl into concrete specimens, preliminary prediction model was established considering how measuring instruments and sizes of rebars incfluenced on corrosion current density with the real corrosion current density under two different water-cement ratios and four different amounts of chloride ion added into fresh concrete. Furthermore, from the experimental datas of the accelerated corrosion test for bare steel rebars, Coefficients of correction to corrosion current density was obtained mainly considering how inhibitors, measuring instruments, sizes of rebars and corrosion types incfluenced on corrosion current density, and then preliminary prediction model was modified by these coefficients of correction. The correction results demonstrated that red lacquers was the best inhibitors to prevent rebars from corrosion, and the corrosion inhibition efficiency of D10 and D22 were 95% and 75% respectively; under the identical corrosion conditions, sizes of rebars had no influence on real corrosion current density, but influenced on real weight loss ratios; under the identical corrosion conditions, corrosion surface area on the measured region had no effect on the real corrosion current density and weight loss ratios; the research suggested that using GalvaPulse to predict corrosion current density of strictly corroded rebars was feasible, but picking the average measured values of GalvaPulse and Gecor8 to predict corrosion current densitie of initially corroded rebars was reasonable. After the long-term corrosion current density prediction model was accomplished, the corrosion current densities at the specific structure ages were able to be predicted and correspond weight loss ratios were calculated. Consequently, these weight loss ratios were imported into RC seismic model to evaluate residual seismic capacity and formulate improvements after structure ageing and deterioration happened. Owing to protections of covering materials on the surfaces of concrete were not considered when experiments were designed, most of weight loss ratios calculated were beyond the available range of the mechanical reduction model at the age of 60 years after the prediction model had been finished. Therefore, deteriorated structures besides the target structures will be regarded as examples to modify the real corrosion current density considering how covering material influenced on the prediction model if the results were applied to ordinary structures. Finally, the applicable range of long-term corrosion current density prediction model will be promoted, as well as be applied to seismic evaluation of ordinary deteriorated structures. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/49043 |
DOI: | 10.6342/NTU202003173 |
全文授權: | 有償授權 |
顯示於系所單位: | 土木工程學系 |
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