Studies on Origin of Chlorides of RC Structures in Cold Region and Influence of Salts on Freeze-Thaw Resistance of Concrete

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1. Actual Conditions for Application of Deicing SaltsActual conditions for application of deicing salts in the Tohoku district and Niigata prefecture were made clear, then of geographical distribution of spreading amount of deicing salts was drawn up.2. Influence of Deicing Salts(1) The relatively great amount of accumulation of chlorides was observed in concrete curbs collected from the inland of Aomori prefecture, possibly because of the penetration of deicing salts.(2) The geographical distribution and the seasonal change of the sedimented chloride amount were made clear. There existed artificially generated chlorides in some districts. The artificial chlorides was guessed mainly due to the spreading of deicing salts. Comparing the amounts of chlorides in the air monitored by deposit gauge method and gauze method regulated by JIS Z 2381, the different method gave the different amount in monitored chlorides and a little correlation between them was dound.3. Influence of Salts on the Freeze-Thaw Resistance(1) Quantitative evaluation Of surface scaling was possible by the measurement of weighl loss. The effects of chlorides such as deicing salts were serious on the scaling damage and tile degree of damages were different types of chlorides. ASTM C 672-84 method and RILEM tentative method were judged to give nearly the same estimation of the scaling resistance.(2) It was made clear that the chlorides existing in tile concrete moved and concentrated due to the freeze-thaw action.