Evaluation of Jordanian Basalt as a Thermal Insulation Material

Abstract

Finding a thermal insulation material that is naturally available, cheap, and effective for minimising energy losses is a challenge for geotechnical engineers in Jordan. Previous research suggests the use of mineral wool, polyurethane, or air layers as an insulation material but so far, the basalt has not been used as an insulation material in Jordan. The objective of this study was to measure and compare the thermal conductivity (K), bulk density (ρ B ), porosity (ɛ) and chemical composition of the basalt from Hashemiah area and Hulial mountain in Jordan in order to evaluate the rock as a thermal insulation material. A total of fourteen samples, seven for each zone, were evaluated. The thermal conductivity was measured using transient plane source technique (TPS) at ambient temperature. Porosity and density were measured by the standards of the American Society of Testing Materials (ASTM). The chemical composition of the samples was analysed by X-Ray diffraction to include the effect of aluminium oxide on thermal conductivity analysis. Experimental values covered the range of ɛ between 0.008-8.7%; ρ B between 2.54-2.93 g/cm 3 and K between 1.62-2.98 W/mK. The experimental K values were compared with allometric fit and theoretical prediction models. In general, thermal conductivity tends to decrease with porosity in basalt samples. This study found increasing conductivity values with ɛ when ferromagnesian-aluminium oxide concentration reached levels above 38% and porosity less than 4% indicating that high percentages of these oxides decrease the insulating effect of the air in the empty spaces of the basalt at reduced porosity levels. Low values of conductivity and percentage of ferromagnesianaluminium oxides characterise the Jordanian basalt in the Hashemiah area and makes it better for insulation than the Hulial mountain basalt. The experimental values presented in this work are important for predicting the optimum insulation thickness and predicting energy losses in construction buildings where basaltic rocks are used.