Improvement of Malagasy Traditional Earth Bricks by Using a Derivative of CNSL as a Binding Agent

Traditional bricks are still the most widely used building material in Madagascar. Bricks are made from clay that is fired for weeks in open-air kilns (600–750 °C) by using rice husks, peat, charcoal, coal, and wood as fuels. This process contributes significantly to environmental pollution by emitting CO2 and particles. In addition, the intensive use of wood and charcoal is partly responsible for the deforestation that still taking place on the “Red Island”. The development of sustainable building materials is therefore of global interest. This research provided a solution by implementing the oxyacetic acid derivative of cashew nut shell liquid (CNSL) as a binder to reduce energy consumption in the preparation of earthen materials. This product was obtained from cashew nut waste and was used in a proportion of 5 to 15% with the red soil of Madagascar. The materials were formulated at a much lower temperature (60 °C) compared to the traditional process for 24 to 48 hours in a custom-designed mold. The material with 10% oxyacetic binder from CNSL was a compact, hard solid with higher mechanical properties, including a twice higher compressive strength (5.6 MPa compared to 2.2 MPa) and a higher tensile strength (2.2 MPa compared to 1.6 MPa). This material also had better water resistance after 2 months of immersion; traditional clay bricks absorbed 36.65% of the water, and the material with binder only absorbed 12.62%. This research demonstrates that the utilization of local agricultural waste as a binder is a viable strategy for reducing the carbon footprint of traditional building materials while significantly improving their physico-mechanical properties.