Thermal conductivity measurement in clay dominant consolidated material by Transient Hot-Wire method.

Abstract

The transient hot-wire (THW) technique is widely us ed for measurements of the thermal-conductivity of most fluids and some attempts have also been carried out for simultaneous measurements of the thermal-diffus ivity with the same hot wire. This technique was also tried to determine thermal prope rties of soils by the mean of probes which can be considered as wire with some assumptions. The purpose of this paper is to validate the thermal conductivity measurement by th e THW technique in geomaterials, composed of compacted sand + clay mineral that can be used for earth construction (Compacted Earth Brick). The thermal transfer behaviors are mainly governed by the texture and moisture of the geomaterials. Thus the investigations were performed (1) in media made of glass beads of different diameters in dry and saturated state in order to observe the role of grain sizes and saturation stat e on the wire temperature (Δt) measurements and (2) in the compacted clay-geomaterial at different moisture states. The Δt / ln(t) diagrams allow the calculation of two the rmal conductivities. The first one, measured in the short time acquisition (< 1s), char acterizes the microtexture of the material and its hydrated state. The second one, me asured for longer time acquisitions, characterizes the mean thermal conductivity of the material.