Laboratory test methods for determining freeze resistance of unbound materials in road pavements

Freezing and ground water in road constructions have a strong influence on the asphalt layer and unbound layer of road pavement. This is also one of the main problems that lead to many and frequent remediation works of all types of roads in Slovenia. After winters with temperatures under 0 °C, asphalt layers become full of cracks and other damages. Over the last years, remediation work with different types of retreatment is increasingly used instead of reconstructing with excavation of the entire sub-base layer and changing the material with new, freeze-resistant material. These new technologies influenced the development of a new method for determining freeze resistance of recycled material.
Remediation work on a national road in the western part of Slovenia was done with in-situ pavement retreatment, which includes mixing old unbound material with reclaimed asphalt pavement (RAP) and 3 % of cement. The testing method and requirements for freeze-resistant material are prescribed (amount of fine particles, particle size distribution, etc.) in the National technical specifications for road constructions. The prescribed method for determining freeze resistance is time consuming and takes approximately a month. Our main task was to find a method that will be as reliable as the method prescribed in the National technical specifications, but would not take more than a week. Following that goal and also finding the limited amount of allowed fine particles content for studied retreatment work, two different types of freeze tests were performed with the excavated material. The results from laboratory tests are presented as well as the method developed for determining freeze resistance of unbound in-situ retreatment material.