LAUSR

Abstract The study reported in this paper was undertaken to investigate the feasibility of lightweight construction materials, based on vegetable fibres. This innovative material consisted of mixture of natural clay (60%) and natural sand (40%) reinforced with different levels of fibers extracted from Jancus acutus “Smar”. The fibers were used as partial replacement of sand in mixture by volume at: 0% (Control Specimen), 5%, 10%, and 20%. The objective of this work is to evaluate the physico-mechanical properties, through the examination of materials lightning, mechanical strengths (compressive and flexural). Due to the high hygroscopic nature of the vegetable fibers, the thermal conductivity of the composite materials was measured at both wet and dry state at different volumes of Juncus fibers replacement. Test-results have shown that the addition of 20% fibers decreased the composite bulk density from 1900 kg/m3 to 1100 kg/m3, which results in a high reduction of mechanical performances in terms of compressive and flexural strengths. The experimental investigation of thermal behaviour of this composite has shown that the increase of fibers volume leads to a significant decrease in thermal conductivity. For a composite containing 20% of fibers replacement, the dry thermal conductivity decreased from 0.902 W/m.K for control specimen (without fibers) to a value of 0.327 W/m.K. However, at wet state, the corresponding thermal conductivity decreased from 1.543 W/m.K to 0.361 W/m.K. Despite the decrease in mechanical strengths, the resulting composite can thus be considered as a promising candidate for use in thermal insulation material, because a conductivity of 0.350 W/m.K is generally considered as the worst acceptable value for insulating building material.