These methods are normally based on similar assumptions—namely, in saturating a mixture with water (with or without negative pressure, that is a vacuum) and holding it there at a fixed temperature for a given time. Afterward, a strength test is conducted, most often using one of the following methods:
• Marshall stability
• Resilient modulus at different temperatures
• Indirect tensile strength
The comparison of results for specimens conditioned in water with those untreated in water determines the water resistance of an asphalt mixture.
In an extended variant, specimens saturated with water are subjected to many cycles of freezing and thawing to find the mixture’s susceptibility to water and frost. Another variant that involves freezing specimens previously saturated with an aqueous solution of NaCl (e. g., 2%) has also been used. This is a much more effective test due to the aggressive action of the aqueous solution of salt on binder adhesion to the aggregate. This kind of test is often conducted in countries with colder climates.
