Action of Frost on Concrete

Damage of concrete in aggressive media is accelerated by ice formation. There are several factors affecting the destraction of concrete as a result of capillary water freezing. Water does not freeze in the gel pores, because they are too small for stable ice nuclei formation. The monomolecular layer of adsorbed water, bound with the surface forces, does not freeze too. The temperature of water freezing in capillaries varies with capillary diameter, it is assumed as equal of about -15 °C. The permeability of concrete is an important factor, because water is penetrating into it as a result of capillary action. The process occurs significantly more rapidly when concrete is under the unilateral hydrostatic water pressure. 

In Fig. 6.75 the relative rate of hydration is shown in respect to the rate of hydration at temperature of 20 °C. According to the authors [278] this curve showing the hydration rate can be described with Arrhenius equation. However, it seems that too high simplifications were assumed. However, the experimentally derived relation, in which the heat of hydration will be used, is well adjusted to this curve. 

In the case of hardened concrete the saturation with water is a very important as a factor of frost resistance. Some authors propose the following relation for the degree of critical water saturation of concrete  

This question is discussed in details in a book by M Pigeon and R. Pleau, Durability of Concrete in Cold Climates , Taylor Francis, London and New York 1995. 

Fagerlund [322] presented a method for determination of the critical degree of saturation (S ) based on modulus of elasticity measurement after six freezing and thawing cycles (Fig. 6.76a). 

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