Steady-state thermal measurement of moist granular earthen materials

A technique based on the heat flow meter method is proposed for measuring the thermal conductivity of moist earthen and granular loose-fill materials. Although transient methods have become popular, this steady-state approach offers an uncertainty that can be reliably estimated and a test method that is widely accepted for building certification purposes. Variations to the standard method are proposed, including the use of a rigid holding frame with stiff base and silicone sponge buffer sheets, in conjunction with difference measurement to factor out the contributions from base, buffers and contact resistance. Using this approach, results are presented for green-roof substrates based on scoria, terracotta and furnace-ash at different moisture contents. Thermal conductivity ranged from 0.13 to 0.80W/mK and fitted well to linear regression plots against moisture content. Further comparative measurements of a single specimen showed that direct measurement was less consistent than difference measurement and thus indicated that thermal resistance was higher by 0.023m(2)K/W, attributable to the presence of contact resistance.