ABSTRACT
During the last decades in Norway, natural (fluvial, glaciofluvial) gravel resources have been substituted with crushed rock material for road and railway construction. However, the thermal properties of these materials in some cases are significantly different compared to natural materials. Therefore, evaluation of thermal conductivity of these diverse crushed rock materials is important.
For engineering purposes, empirical models are widely used to assess the thermal conductivity. Most of the currently developed models are based on soil properties. However, it is observed that thermal conductivity of crushed aggregates can vary significantly due to their particles shape and size, porosity, mineralogy, quartz content and density. Therefore, the use of these models might lead to false results.
In a frost design method, the required parameters of crushed rock aggregates are thermal conductivity, density and water content. The heat transfer during the freezing of natural soils is assumed proportional to thermal conductivity of the material. In the current calculations used by Norwegian Public Road Administration, thermal conductivity of granular layers is considered mostly being below 2 W/mK based on the water content. However, it has been shown that the thermal conductivity of crushed rock materials can vary from 1 to 4 W/mK depending on other material properties in addition towater content.
The main objectives of our investigations are: i) to measure thermal conductivity of crushed aggregates and assess the effect of various mineralogies ii) to use the obtained data to validate an existing empirical model.
