AASHTO T 161:2021 Standard Method of Test for Resistance of Concrete to Rapid Freezing and Thawing.
1 .1. This method covers the determination of the resistance of concrete specimens to rapidly repeated cycles of freezing and thawing in the laboratory by two different procedures: Procedure A, Rapid Freezing and Thawing in Water, and Procedure B, Rapid Freezing in Air and Thawing in Water. Both procedures are intended for use in determining the effects of variations in the properties of concrete on the resistance of the concrete to the freezing and thawing cycles specified in the particular procedure. Neither procedure is intended to provide a quantitative measure of the length of service that may be expected from a specific type of concrete.
1 .2. The values stated in SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents: therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
1.3. All material in this test method not specitically designated as belonging to Procedure A or Procedure B applies to either procedure.
As noted in the scope. the two procedures described in this method are intended to determine the effects of variations in both properties and conditioning of concrete in the resistance to freezing and thawing cycles specified in the particular procedure. Specific applications include specified use in M 194M/M 194, T 157, and ranking of coarse aggregates as to their effect on concrete freeze—thaw durability, especially where soundness of the aggregate is questionable.
3.2. It is assumed that the procedures will have no significantly damaging effects on frost-resistant concrete that may be defined as (1) any concrete not critically saturated with water (that is. not sufficiently saturated to be damaged by freezing) and (2) concrete made with frost-resistant aggregates and having an adequate air-void system that has achieved appropriate maturity and thus will prevent critical saturation by water under common conditions.
3.3. If, as a result of performance tests as described in this method, concrete is found to be relatively unaffected, it can be assumed that it was either not critically saturated or was made with “sound” aggregates, a proper air-void system, and allowed to mature properly.
3.4. No relationship has been established between the resistance to cycles of freezing and thawing of specimens cut from hardened concrete and specimens prepared in the laboratory.
Note 1—There is no apparent reason to expect a difference in performance in these two procedures if the concrete properties are fundamentally the same. However, the fact that these two conditions may have been executed with different consolidation procedures or other procedures could affect the number and size of empty, and possibly water-filled voids, which could affect test resti Its.
3.5. There is no specific guidance in this standard on choosing between Procedure A and Procedure B for a given application, except when contained in another standard. Standards T 157 and M 194M/M 194 both stipulate Procedure A.
AASHTO T 161 pdf download.