Frost resistant concrete

Abstract

There are two basic frost durability problems: internal cracking due to freezing and thawing cycles, and surface scaling, generally due to freezing in the presence of deicer salts. Although there are still parts of the problem which are not perfectly well understood and warrant further investigation, particularly with respect to the differences between laboratory tests and field exposure, the way to make concrete resistant to freezing and thawing cycles is very well known. It is simply to ensure that the hardened concrete has an adequate system of entrained air voids. Field experience as well as laboratory data has shown very conclusively that internal cracking due to frost in properly air-entrained concretes is almost non-existent. Scaling due to freezing in the presence of deicer salts is a much more complex problem than internal cracking for many reasons, but probably mainly because it is related to the microstructure of the very surface layer or ‘skin’ of concrete. Properly air-entrained and properly cured well-designed Portland cement field concretes are generally quite resistant to deicer salt scaling, but scaling still sometimes occurs unexpectedly after only a few years. Research in this area is therefore required. The ability of the commonly used deicer salt scaling tests to predict the performance of concrete under normal field exposure conditions must also be particularly investigated. In addition, research is needed to better understand the process of the formation of large air voids in air-entrained concrete, since the dosage of air-entraining admixtures is based on the total volume of air in the mixture and small dosages that yield an adequate air volume often do not yield an adequate air void spacing factor (and thus adequate frost protection).