Quick freezing of a fragment of rock which is fully saturated with water is, perhaps, the most rigorous of all tests for soundness, durability, or resistance to weathering. So-called soundness or quality tests employed currently, or heretofore, for evaluating concrete aggregates are usually less rigorous inasmuch as the state of saturation at the outset of freezing is not at a critical level. Hence, the number of freeze-thaw cycles endured by a rock specimen undergoing freezing and thawing in the presence of available water may merely reflect the duration of the exposure before the rock becomes vulnerable to damage -- i.e., time required for critical saturation. Damage arises wholly from the combined effects of the volume dilation accompanying the freezing of absorbed water, the dilation pressure induced, and the inherent restraining strength of the aggregate particle. Thus, the severest freezing condition, to which rock or concrete may be exposed, occurs after long periods of sustained wetting -- when the degree of saturation is the highest.

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Report Number

No. 211

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