Public Roads: A Journal of Highway Research, Vol. 28, No. 7

Bostick, T.A.; Brokke, G.E.; Cashell, H.D.; Cope, E.M.; Critz, P.F.; Dimmick, T.B.; French, Alexander; Grieb, W.E.; Johnston, C.M.; Kinter, E.B.; Lewis, R.H.; Lynch, J.T.; Marr, R.A., Jr.; Messer, R.T.; O'Flaherty, Daniel; Olmstead, F.R.; Peck, R.A.; Potter, W.D.; Rex, H.M.; Saal, C.C.; Siess, C.P.; Steele, C.A.; Taragin, Asriel; Teske, W.E.; Timms, A.G.; Viest, I.M.; Vincent, G.S.; Welborn, J.Y.; Werner, George; Wintermyer, A.M.; Woolf, D.O. · 1955 · ROSA P / United States. Government Printing Office

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Summary

This 1955 report by the Bureau of Public Roads summarizes findings from a multi-year investigation into methods for protecting portland cement concrete pavements from scaling and disintegration caused by calcium chloride and other thawing agents. The research was motivated by the widespread use of de-icing salts, particularly in Northeastern states, which frequently resulted in severe surface deterioration of concrete highways. The study aimed to identify mix designs, admixtures, and surface treatments that could enhance concrete resistance to chloride attack. The research comprised two main components: laboratory tests involving artificial freezing and thawing cycles, and outdoor exposure tests conducted over three winters (1951–1954). The laboratory investigation examined five variables: the effect of air content exceeding the standard 6 percent limit; surface coatings of crankcase oil (undiluted and diluted with gasoline); admixtures of paraffin, asphaltic base, and used crankcase oils; the impact of varying thawing agent amounts and types (including urea and rust inhibitors); and the use of vacuum treatment during concrete placement. The outdoor tests evaluated the performance of 27 commercial air-entraining admixtures, the effect of cement alkali content, the substitution of fly ash for cement, curing methods, and vacuum treatment under real weather conditions. Key findings indicated that air content was the most critical factor in resisting scaling. Laboratory results showed that air contents exceeding 6 percent provided significantly better protection than increasing cement content, with 13 percent air content offering substantial resistance after 60 cycles. Surface treatments proved effective only when applied to cured concrete; mineral oil coatings delayed scaling, with multiple coats offering slight benefits over single coats. However, applying oil to plastic (fresh) concrete was detrimental, accelerating scaling. Regarding admixtures, paraffin and asphaltic base oils were ineffective, while used crankcase oil helped retard scaling by entraining air. Replacing cement with fly ash was found to be detrimental to chloride resistance. Additionally, concrete made with low-alkali cement (Brand B) performed better than high-alkali cement (Brand A). Vacuum treatment improved resistance only when concrete was cast on sand bases, not metal bases. Urea caused less rapid scaling than calcium chloride but still resulted in deterioration. The study concludes that maximizing entrained air within specification limits is the most effective strategy for preventing scaling. Protective oil coatings are viable if applied to cured surfaces but are vulnerable to mechanical damage like tire chains. The findings underscore the importance of mix design and curing practices in mitigating the damaging effects of de-icing chemicals on highway infrastructure.

Key finding

Air content exceeding 6 percent was more effective than increasing cement content in resisting scaling, and mineral oil surface treatments applied after curing improved resistance while application to plastic concrete decreased it.

Methodology

mixed_methods

Provenance

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• road surface friction