ABSTRACT
Transportation infrastructures built in cold regions with underlaying frost susceptible subgrade soils may require a frost protection layer. The national guidelines for road construction in Norway provide three distinct design concepts for frost protection layers. The layer can consist of granular stone material (natural or crushed rock), lightweight aggregates (foam glass or expanded clay) or extruded polystyrene (XPS). To better investigate the performance of different frost protection materials, Norwegian Public Roads Administration constructed a series of test sections within a newly reconstructed highway. The test site is located outside Trondheim and is a part of the national level road E6. The test site consists of seven test sections, each 50 m long. All sections have the same thickness of asphalt layers, base layer, and subbase layers. The variation of the test section is within different materials used for frost protection. One section included XPS, two sections were built with lightweight aggregate materials and four sections were built with granular stone material with different gradations. The test site was constructed during the fall of 2018. The winter of 2020/2021 had a freezing index of 9938°C·hours. The results show that sections constructed with lightweight aggregates and XPS provides very similar effect and are overall most efficient to limit the frost penetration. All granular stone materials, except 22/180 mm crushed rock provides moderate frost protection. Crushed rock with 22/180 mm is the least effective and in this section the frost front reached the subsoil. Measured values of frost depth in sections with granular materials agrees well with predicted values from N200 handbook. Values of frost depth from sections with lightweight aggregates and XPS are difficult to compare to the predicted values. However, these sections are substantially overdesigned based on the current guidelines and could be constructed using less material for frost protection layer.
