Evaluation of Several Types of Curing and Protective Materials for Concrete: Part IV: Final Report on Performance

About the report:

Various curing and/or protective coatings were evaluated under three conditions: (1) accelerated laboratory freezing and thawing of specimens in 2 percent sodium chloride solution, (2) exposure in an outdoor area of slabs subjected to controlled application of deicers, and (3) exposure of some of the materials on three bridges. The performance of the outdoor slabs and bridge decks has been observed over the interim since the last report (Newlon 1973). Based upon observations after exposure of the outdoor slabs and the field test sections for five winters, the conclusions from the three previous parts of this report were confirmed. The following conclusions and recommendations are presented. (1) Properly entrained air is overwhelmingly the most effective defense against scaling caused by deicing chemicals. The fact is evident from the excellent performance of the outdoor exposure slabs after intensive deicing for five years and the absence of scaling on the bridge decks, which also were built with concrete that was uniformly and adequately air entrained. (2) When insufficient entrained air is obtained, linseed oil treatments delay the onset of scaling but do not prevent it. (3) Materials of the type studied that are designed to cure and protect concrete in a single application are not effective since the two functions are mutually exclusive (one requires the retention of water while the other requires keeping it out) and they should be thought of as two separate operations. Some of the materials may meet the requirements and be useful for either or both functions, but not simultaneously. (4) Linseed oil treatments applied after curing with a white pigmented, resin based compound of the type specified by the Virginia Department of Highways & Transportation are effective without prior removal of the curing compound. (5) Under intensive and controlled applications of deicing salts, chloride contents at depths 2" (50 mm) below the surface approached the threshold level (about 0.05 percent by weight) for steel corrosion after five years in properly air entrained concrete. In the non-air entrained concrete, the chloride content at the same depth was about double that value. The chloride content was not influenced by curing or protective treatments.

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