Thermal conductivity of base-course materials

Abstract

This paper presents the results of a comprehensive laboratory study on the thermal conductivity of dense and broadly graded coarse base-course materials used in pavements. Materials were selected from eight quarries along the axis of the St. Lawrence River to include a variety of samples of different geological origins. Nearly 200 tests were performed in a thermal conductivity cell using Pyrex heat flux meters to characterize the relationships between the thermal conductivity of unfrozen and frozen samples and the water–ice content. Sixteen tests were also performed on solid rock cylinders to characterize the influence of mineralogy on the thermal conductivity of solid particles from the selected quarries. The most widely used empirical prediction models for thermal conductivity of soils from the literature were found inappropriate to estimate the thermal conductivity of base-course materials. An improved model using the geometric mean method to compute the thermal conductivity for the solid particles and the saturated materials, a modified form of the geometric mean method to predict the thermal conductivity of dry materials, and empirical relationships to assess the normalized thermal conductivity of unfrozen and frozen base-course materials are presented. This new model predicted well the thermal conductivity for more than 150 unfrozen and frozen coarse sand and gravel samples from the literature. A step by step methodology is proposed to assess the thermal conductivity of base-course materials.Key words: base course, porosity, degree of saturation, mineralogy, unfrozen–frozen, thermal conductivity.

Colloquium 2016: Assessment of subsurface thermal conductivity for geothermal applications

“…for example, those used with granular construction materials (Côté and Konrad 2005;Côté et al 2013). The methods that have been used so far in the geothermal heat pump sector are described below.…”

Impact of soil compaction and wetness on thermal properties of sloping vineyard soil

“…Soil thermal properties including thermal conductivity, heat capacity and thermal diffusivity are required in numerous agricultural, meteorological and industrial applications [9,33]. They play an important role in the surface-energy partitioning and resulting temperature distribution [12,21,28] and moisture flow and consequently form the soil and near ground atmosphere microclimate for plant growth [19,27] and the grape quality (e.g.…”

Assessment of structure effects on the thermal conductivity of two-phase porous geomaterials

“…7a). The data from Côté and Konrad [36] for packs of crushed quartzite, granite and syenite saturated with air gave j 2P values of 0.075, 0.105 and 0.120, respectively (Fig. 7b).…”

“…It is, however, possible that the increase in k is caused by higher quartz content, which, in turn, lead to higher k s values in the geomaterials with larger sand particles [4,5,38,39]. The reader should, however, keep in mind that in three-phase porous geomaterials (solid-liquid-gas) the grain size distribution will influence the water distribution in pore-space according to material type giving thus different thermal bridge effect at the solid-to-solid contacts, which influence the effective thermal conductivity as observed experimentally [3,4,36] and numerically [40].…”