新拌及硬固混凝土水溶性氯離子含量檢測之研究

本研究設計0.06、0.121、0.272、0.483 kg/m3等四種不同氯離子含量之新拌和不同齡期硬固混凝土試體，依據CNS 13465之硝酸銀滴定法、電子式氯離子量測法及CNS 14703之微電位計滴定法，分別量測其氯離子含量，比較三法之準確性，其中水溶液之氯離子含量之檢測亦比較之。試驗結果顯示，量測氯離子水溶液準確性最佳為硝酸銀滴定法，平均誤差百分比為4.77%。量測新拌混凝土氯離子含量乃依據CNS 13465中之前處理步驟，結果以電子式氯離子量測法為最佳，硝酸銀滴定法次之，平均誤差百分各為29.7%、39.2%，恰為規範所提示之方法。量測硬固混凝土氯離子含量乃依據CNS 14703中之前處理步驟，結果以硝酸銀滴定法為最佳，平均誤差百分比為8.6%，與規範所提之微電位計滴定法不同，但氯離子含量大於0.4 kg/m3時，不論誤差值或誤差百分比皆顯示微電位計滴定法為最佳。另外，硬固混凝土中氯離子含量可能隨養護水流失，其隨著養護時間增長而遞減。

關鍵字

氯離子含量；新拌混凝土；硬固混凝土；硝酸銀滴定法；微電位計滴定法

並列摘要

The study designed several fresh concrete specimens and harden concrete specimens of different ages, which including four different chloride ion contents of 0.06, 0.121, 0.272, and 0.483 kg/m3. According to the silver nitrate titration method and the electronic instrument method of CNS 13465 as well as the potentiometer titration method of CNS 14703, the chloride ion contents of specimens were measured by each method to compare the accuracy of these three methods. The chloride ion contents of water solution measured by these three methods were also compared. The test results show that, the silver nitrate titration method has the best accuracy in measuring chloride ion content of water solution. The average error percentage is 4.77%. The pre-process steps for the chloride ion content measurement of fresh concrete is that in CNS 13465. As a result, the measurement by the electronic measurement method is the best. The silver nitrate titration method is the second best. The average error percentages are 29.7% and 39.2% respectively. The result is accordance with that in CNS 13465. The pre-process steps for the chloride ion content measurement of harden concrete is that in CNS 14703. The measurement by the silver nitrate titration method is the best. The average error percentage is 8.6%. The result is not accordance with that in CNS 13465, where the potentiometer titration method is described. However, when the chloride ion content is larger than 0.4 kg/m3, the measurement by the potentiometer titration method is the best either compared by error value or by error percentage. In addition, the chloride ion content in hard concrete may flow away with curing water since it decreases with curing time.