Investigation of crushed rock material used in the frost protection layer

Norwegian road construction practice has changed significantly during the last 40 years due to the replacement of gravel by crushed rock materials in the granular layers of the pavements. Knowledge of thermal conductivity of all granular layers is required in order to calculate of frost penetration depth. This paper presents the results of field and laboratory investigations of crushed rock materials used in the frost protection layer. Field observations did not show direct connection of frost heave of the surface with the amount of fines content in the granular layers. Laboratory experiments on thermal conductivity revealed that increasing the water content from 0 to 7% increases thermal conductivity of granular materials from 1.5-2 to 4-7.5 W/mK in frozen and up to 3-6.2 W/mK in unfrozen states.