**4. Factors that affected the freeze/thaw resistance**

Susceptibility to freeze/thaw damage is affected by the concrete's composition, permeability, porosity, type, moisture content, age, air-entraining admixtures, workability, exposure environment, and aggregate type. Where it observed that the key factors relevant to freeze/thaw durability are the air void characteristics especially in the case of using admixtures, they should compatible, in concrete and high quality of aggregate. As well as mix design limitations according to BS EN 206:2013 + A1:2016 [17] are to be considered necessary [18].

Yet not sufficient conditions for achieving high frost resistance of concrete, especially when exposed to severe frost, wet conditions, and high levels of de-icing agents. Thus, following the principles transpiring from the literature's observations during the design of freeze/thaw resistance concrete can be highly beneficial. Some of these observations have been concluded as [11]:

• High-quality aggregate should be used featuring appropriate frost resistance tested in NaCl solution and water, high resistance to fragmentation, continuous grading, and minimal water requirement.

*Concrete Performance in Cold Regions: Understanding Concrete's Resistance… DOI: http://dx.doi.org/10.5772/intechopen.99968*

• When specifying admixtures like Supplementary cementing materials, to concrete it is necessary to check their compatibility by valuating the air void characteristics in hardened concrete, and this concerns in particular airentraining and water-reducing admixtures.

The severity of freezing (minimum temperature); rate of fall of air temperature (rate of freezing); change of air temperature during periods of freezing; the number of freeze/thaw cycles and the presence of de-icing salts is the major environmental aspects and critical factors that are participated in the developing of freeze/thaw damage.
