The use of natural fibers to enhance the thermal properties of earth bricks has become increasingly popular. This study investigates the thermal performance of termite mold soil (TMS) reinforced with two types of fibers: coconut fibers (CF) and empty fruit bunch spikelet fibers (EFBSF). Various fiber compositions (0%, 0.5%, 1%, 1.5%, 2%, and 2.5%) were combined with sodium hydroxide (NaOH) treatments at concentrations of 1%, 2%, 3%, and 4%. Laboratory results reveal that TMS exhibits promising physical properties, including a moisture content of 23.64%, a maximum dry density of 1.63 g/cm³, and a plasticity index of 20%, indicating its structural stability and suitability for earth block production. The study also analyzes the chemical properties of EFBSF and CF fibers, noting that CF has a higher holocellulose content (88.0%) compared to EFBSF (33.5%), which impacts moisture retention and structural integrity. Thermal analysis demonstrates that incorporating these natural fibers significantly enhances the thermal performance of TMS. With a 2.5% fiber content, CF reduces thermal effusivity from 1771.43 J/m²Ks^1/2 to 1079.39 J/m²Ks^1/2 and thermal conductivity from 0.86 W/mK to 0.38 W/mK, making it particularly effective in improving insulation in hot conditions. EFBSF also lowers thermal effusivity and conductivity, but to a lesser extent than CF. Additionally, the presence of these fibers reduces volumetric calorific capacity, with CF showing a more pronounced effect. Overall, TMS reinforced with coconut fibers, especially at 1% NaOH and 2.5% fiber content, offers the best thermal performance, suggesting its potential for sustainable construction. This research promotes the use of locally sourced, natural fibers in earth block manufacturing, contributing to the development of more energy-efficient and environmentally friendly building materials.
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