Thermal Conductivity of Pyroclastic Soil (Pozzolana) from the Environs of Rome

The paper reveals the experimental procedure and thermo-physical characteristics of a coarse pyroclastic soil (Pozzolana), from the neighborhoods of Rome, Italy. The tested samples are comprised of 70.7% sand, 25.9% silt, and 3.4% clay. Their mineral composition contained 38% pyroxene, 33% analcime, 20% leucite, 6% illite/muscovite, 3% magnetite, and no quartz content was noted. The effective thermal conductivity of minerals was assessed to be about 2.14W·m−1·K−1. A transient thermal probe method was applied to measure the thermal conductivity (λ) over a full range of the degree of saturation (Sr), at two porosities (n) of 0.44 and 0.50, and at room temperature of about 25 ◦C. The λ data obtained were consistent between tests and showed an increasing trend with increasing Sr and decreasing n. At full saturation (Sr = 1), a nearly quintuple λ increase was observed with respect to full dryness (Sr = 0). In general, the measured data closely followed the natural trend of λ versus Sr exhibited by published data at room temperature for other unsaturated soils and sands. The measured λ data had an average root-mean-squared error (RMSE) of 0.007W·m−1·K−1 and 0.008W·m−1·K−1 for n of 0.50 and 0.44, respectively, as well as an average relative standard deviation of the mean at the 95%confidence level (RSDM0.95) of 2.21% and 2.72 % for n of 0.50 and 0.44, respectively. B V. R. Tarnawski vlodek.tarnawski@