Int J Thermophys (2017) 38:21 DOI 10.1007/s10765-016-2161-y Thermal Conductivity of Pyroclastic Soil (Pozzolana) from the Environs of Rome M. L. McCombie 1 · V. R. Tarnawski 1 · G. Bovesecchi 2 · P. Coppa 2 · W. H. Leong 3 Received: 19 July 2015 / Accepted: 21 November 2016 © Springer Science+Business Media New York 2016 Abstract The paper reveals the experimental procedure and thermo-physical charac- teristics 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 2.14 W·m −1 ·K −1 . A tran- sient thermal probe method was applied to measure the thermal conductivity (λ) over a full range of the degree of saturation ( S r ), 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 S r and decreasing n. At full saturation ( S r = 1), a nearly quintuple λ increase was observed with respect to full dryness ( S r = 0). In general, the measured data closely followed the natural trend of λ versus S r 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 0.007 W·m −1 ·K −1 and 0.008 W·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 (RSDM 0.95 ) of 2.21 % and 2.72 % for n of 0.50 and 0.44, respectively. B V. R. Tarnawski vlodek.tarnawski@smu.ca 1 Division of Engineering, Saint Mary’s University, Halifax, NS B3H 3C3, Canada 2 Department of Industrial Engineering, University of Rome “Tor Vergata”, via del Politecnico 1, 00133 Rome, Italy 3 Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canada 123