Exploring the potential of biochar additives to improve the mechanical and thermal properties of hempcrete

Abstract

The construction industry, which accounts for nearly 40% of worldwide energy use, is under growing pressure to implement sustainable practices. Traditional insulating materials like rock wool and polystyrene contribute significantly to carbon emissions due to their high embodied energy, highlighting the need for environmentally friendly alternatives. As sustainability becomes a global priority, many countries are implementing policies aimed at reducing carbon dioxide emissions. In developed countries, a significant portion of energy is consumed for heating and cooling, making building energy efficiency and HVAC system optimization critical. The use of materials that passively regulate room temperature and humidity offers an effective means of reducing energy use. (Konsinski et al., 2022). Hempcrete, a biocomposite made from hemp shives, water, and lime, offers a promising sustainable alternative, providing effective thermal and acoustic insulation as well as fire resistance. However, its mechanical strength is typically insufficient for large-scale construction, limiting its application to non-load-bearing structures due to its high-water absorption (Maris Sinka et al., 2015). This research investigates the potential of improving the mechanical and thermal properties of hempcrete while reducing its water absorption by incorporating untreated and chemically treated hemp shives with biochar at 1% and 2% volume ratios, combined with natural hydraulic lime. This study aims to explore the effectiveness of incorporating biochar as an additive in hemplime composites. Biochar particles are expected to reduce overall water absorption by forming a barrier between fibers and water molucules, while maintaining the material’s thermal insulation properties. The research includes thermal conductivity tests to evaluate insulation performance, mechanical tests (compression and flexural) to assess strength, and water absorption tests. Results demonstrated that the chemical modification of hemp shives along with the inclusion of biochar significantly improved the material’s thermal conductivity, achieving values between 0.0272 W/mK to 0.0549 W/mK, and reduced water absorption by 0.68 % to 9.31%. These findings suggest that biochar-enhanced hempcrete could surpass traditional commercial materials in both sustainability and performance.