Durability characteristics of certain foamed asphalt mixtures were established during this laboratory investigation. Durability was characterized by a water sensitivity test and cyclic freezing and thawing. The various foamed asphalt mixtures were evaluated for durability after the mixtures had been compacted into 10.16-cm (4.00-in.) diameter by approximately 6.35-cm (2.50-in.) high specimens, and cured.

Durability effects of different variables were determined in this laboratory study. These variables were foamed asphalt content (two levels for water sensitivity section, one level for freeze-thaw section), aggregate (three types, used in both sections), additives (three types, plus a set without additives), and additive content (two levels for each additive in the water sensitivity section, one level for each additive in the freeze-thaw section). One asphalt type, one mixing and testing temperature, one set of curing conditions, and one moisture content per aggregate were used.

Resilient modulus and modified Marshall stability tests were used to monitor durability characteristics of the mix in the water sensitivity section. Durability in the freezing and thawing section was monitored by pulse-velocity, resilient modulus, and modified Marshall stability tests. When lime was used as an additive, durability, strength, and longevity of the foamed asphalt mixtures were substantially improved. The improvement achieved with the addition of lime was such that a material generally less suitable for bituminous mix, such as outwash sand or pit-run gravel, may rival a material more suitable for bituminous pavement mix such as crushed limestone.

During this study there were similar rates of decline per freeze-thaw cycle for pulse-velocity and modified Marshall stability. Pulse-velocity, a nondestructive test, appears to be related to the destructive modified Marshall stability method. There seemed to be a good reproducibility of pulse-velocity values among similar specimens.