Freeze-thaw attack damage

The duration and quality of cure of the fresh mix determine the hydration progress and the volume of hydration products, which may eventually fill up the capillary pores and reduce their permeability. For reduced w c and prolonged cure the pore size distribution diagrams are shifted towards smaller sizes, with decreasing total volume. The saturation of capillary pores plays an important role in the composite durability if the material is exposed to freeze-thaw cycles. Damage is more probable when the critical value of the saturation is attained and the increasing volume of ice cannot be accommodated without additional stresses. The hardened paste density is also important to ensure resistance against all other external attacks. 

A preliminary assessment of the condition of the structure is required. Techniques described in Chapter 16 may be used to diagnose the causes of deterioration and the extent of damage. Degradation processes that may indirectly contribute to corrosion of the reinforcement (freeze-thaw, sulfate attack, etc.) should also be considered. Distinction should be made between different parts of the structure where ... 

Corrosion is not the only deterioration mechanism in reinforced concrete. Alkali-silica reactivity (ASR), sulphate attack, thurmasite attack, delayed ettringite formation, freeze thaw, thermal movement, settlement and other movement can all lead to concrete damage and their assessment must be included in the surveys. 

Petrographic examination. Petrographic examination is a microscopic analysis of concrete, performed on core samples removed from the structure. Further details may be foimd in the ASTM C856 standard. It yields information such as the depth of carbonation, density of the cement paste, air content, freeze-thaw damage, and direct attack of the concrete. 

Besides corrosion-induced rebar damage, there are three other commonly cited forms of concrete degradation, namely, alkali-aggregate reaction, freeze-thaw damage, and sulfate attack. 

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