以貯鹽試驗探討鋼筋混凝土之臨界氯離子濃度

Using Salt Ponding Test to Evaluate the Chloride Threshold Level in Reinforced Concrete

何季軒(Jih-Shiuan Ho)

指導教授 ： 詹穎雯

國立臺灣大學/工學院/土木工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01611

摘要

鋼筋混凝土建材現今已非常普及，但混凝土內之鋼筋若腐蝕容易造成結構物局部強度損失及安全疑慮。台灣地區四面環海，氣候特性屬高溫潮濕，沿海地區之鋼筋混凝土結構物易受海風中氯離子侵入。若氯離子侵入量超過臨界值，即會造成鋼筋表層鈍化膜破壞使鋼筋開始腐蝕。因此了解鋼筋混凝土材料抵抗氯離子入侵的能力是一項重要的課題。
本研究中的試體將分為水膠比0.45、0.55及0.65三種系列及五種卜作嵐材料取代量，以貯鹽試驗使氯離子侵入鋼筋混凝土。在貯鹽試驗進行過程中以美國James儀器公司製作的 Gecor 8 腐蝕電流儀進行腐蝕電流密度量測。並在貯鹽試驗結束後以酸溶性氯離子含量檢測技術測得混凝土內氯離子分佈，再以菲克定律計算出不同配比的擴散係數，以作為混凝土對鋼筋保護程度之參考。
實驗結果顯示擴散係數會隨著混凝土緻密性提升而降低，臨界氯離子濃度則是在水膠比較高的配比有較大的值。而鋼筋表面腐蝕情形也指出在相同的腐蝕表面積下較高的水膠比會對應較大的總氯離子濃度。

關鍵字

臨界氯離子濃度 ； 擴散係數 ； 腐蝕電流密度 ； 貯鹽試驗

並列摘要

Reinforced concrete material has been generally used in our daily construction, but corrosion of the steel rebars may decrease the strength and increase the risk of collapse. Taiwan is surrounded by the ocean, the chloride ion would invade reinforced concrete structures by the sea wind. The steel rebar will depassivate and start to corrode when the accumulation of the chloride ion exceeds a critical value. Therefore, understanding the resistance of reinforced concrete from chloride ion intrusion is an important issue.
In this study, the specimens are divided into three groups by different water-cement ratio ( 0.45,0.55 and 0.65 ). There are five substitution ratio of pozzolanic material for cement in each group. Salt ponding test is used to prompt the chlorine ion to invade reinforced concrete specimens. Corrosion current density measured by Gecor 8 corrosion current instrument is taken to be the norm of corrosion. The chloride ion content is gauged by acid-soluble method after the end of salt ponding test. The distribution of chloride ion in concrete is simulated by Fick's Law.
Experimental results show that the diffusion coefficient will decrease with the increasing of concrete density. The chloride threshold value increase with the increasing of water-cement ratio. The observation of the surface of steel rebars also points out the specimens with higher water-cement ratio are provided with higher chlorine ion concentration under the same corrosion area.

並列關鍵字

chloride threshold level ； diffusion coefficient ； corrosion current density ； salt ponding test.

參考文獻

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