Thermal Diffusivity of Peat-Sand Mixtures with Different Peat and Sand Contents

Abstract

Abstract: The thermal diffusivity of sieved quarry sand with a predominance of a fraction of 0.05–0.25 mm, lowland packed peat, and their mixtures was studied. The sand was mixed with the peat in various proportions; the peat content in mixtures ranged from 1 to 80% by dry weight. Metal cylinders of 10 cm in height and 3.8 cm in diameter were filled with sand, peat, and peat-sand mixtures. Thermal diffusivity was measured in laboratory by the unsteady-state method with a working temperature range of 20–26°C. The heating rate of the packed samples was measured after the samples were placed in a liquid-bath thermostat with a constant water temperature. For each sample, a series of measurements was carried out with a step-by-step change in the water content from the maximum one after capillary saturation of the sample to the minimum one corresponding to the air-dry state. The thermal diffusivity vs. water content dependence was almost linear for peat; for sand, it was a curve with a maximum. The lowest thermal diffusivity value was obtained for peat and mixtures with low sand contents; the highest one, for pure sand. Within the studied range of water contents, the thermal diffusivity of different samples changed by a factor of 1.3–2.8. The nonlinear character of the thermal diffusivity vs. peat content dependence was revealed. Small additions of peat to sand resulted in a noticeable decrease in the thermal diffusivity of the mixture; small additions of sand to peat had practically no effect on thermal diffusivity. The thermal diffusivity of the studied substrates increased with increasing bulk density and sand content of the sample and decreased with increasing organic matter content.