This report evaluates the results from corrosion investigations on twelve 50 year old bridges on the A82 trunk road between Bridge of Orchy and Invergarry in Scotland. The bridges experience a harsh environment and have been treated with de-icing salts since the mid 1960's. Superstructural elements were surveyed by a contractor for reinforcement corrosion using half-cell potential, electrical resistivity, carbonation, chloride and cover measurements. These tests were supplemented by petrographic examinations of thin sections from cores and by measurement of compressive strength, density, cement and sulphate content to assess the condition of the concrete. The investigations showed that the beams and soffits of the decks have suffered the most corrosion as a result of the synergistic action of carbonation and chlorides. Data from the top steel of the decks were more difficult to interpret. (A)

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