32年海工混凝土桩中水溶性氯离子浓度分布

C. Lim, K. Ong, K. H. Law, P. Paramasivam
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引用次数: 1

摘要

由普通硅酸盐水泥制成的混凝土的碱性为作为钢筋的钢筋提供了天然的防腐保护。根据Cl/OH比的不同,少量氯离子的存在往往会破坏钢筋的这种钝化性,即使pH值大大高于11.5。本文利用菲克第二扩散定律,对从新加坡港口码头提取的6个32年历史的海洋桩的大气、潮汐和淹没区获得的水溶性氯化物浓度剖面进行了数值预测。将钢筋水平的水溶性氯浓度与钢筋质量损失进行了比较。采用钻孔和吸力法在抽取桩的整个长度上间隔约1m的位置取样混凝土。结果表明,计算结果与在新加坡条件下得到的水溶性氯离子浓度的实际值吻合较好。所计算的扩散参数均在所用混凝土等级30mpa立方强度的预期范围内。发现钢筋腐蚀的地点与显示水溶性氯化物存在的地点相对应,其浓度低至混凝土质量的0.025%,主要发生在大气区。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Concentration Profile of Water-Soluble Chloride in 32 Year-Old Marine Concrete Piles
The alkaline nature of concrete made from normal portland cements provides a natural protection against corrosion of steel bars embedded as reinforcement. Presence of chloride in small quantities, depending on the Cl/OH ratio tends to destroy this passivity of steel reinforcement even at a pH considerably above 11.5. The present paper compares numerical predictions, using Fick's second law of diffusion, against concentration profile of water-soluble chloride obtained from the atmospheric, tidal and submerged zones of six 32 year-old marine piles extracted from a wharf in the Port of Singapore. Concentrations of water-soluble chloride at the level of steel reinforcement were compared with the loss in mass of the reinforcing bars. The concrete was sampled using the drill and suction method at locations spaced approximately 1m along the entire length of the extracted piles. The results show that the numerical estimates were in good agreement with the actual values of water-soluble chloride concentrations obtained under Singapore conditions. Diffusion parameters calculated were within the expected range for the grade of concrete used, 30 MPa cube strength. Locations where reinforcement corrosion were found corresponded to those that showed presence of water-soluble chloride in concentrations as low as 0.025% by mass of concrete occurring mainly in the atmospheric zone.
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