Thermomechanical and physicochemical investigation of Raw clay bricks derived from Nomayo clay and palm shell powder lignocellulosic material

This study proposes an in-depth characterization of the physicochemical, thermal and mechanical properties of unfired clay bricks derived from Nomayos clay (Cameroon), with progressive additions of palm kernel shell powder bio-based material (0 to 60% by mass). The aim was to assess the influence of lignocellulosic palm kernel shell powder on the physical and mechanical properties of unfired clay bricks, with a view to proposing a sustainable, lightweight, low-cost construction solution. To this end, physical analysis revealed a significant reduction in density (22-35%) with increasing organic matter content, attributed to the lower density of palm kernel shells. Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) confirms a homogeneous distribution of the main elements (C, O, Mg, Fe, Si, Al, Na, K, Ti). X-ray diffraction and Fourier transform infrared spectroscopy analysis show kaolinite as the main mineral phase, with a little amount of quartz and organic functional groups in composite samples. Thermal analysis (TGA/DTA/DTG) indicates a three-stage decomposition process: moisture loss (~ 188 °C), cellulose degradation (~ 314 °C, Δm ≈ 19.17%), and kaolinite dehydroxylation (> 500 °C), with thermal stability reached above 600 °C. Mechanical tests show a progressive decrease in compressive strength from 4.64 MPa (A0%) to 0.12 MPa (A60%), inversely correlated with organic filler content. Despite the decline in mechanical performance, these bricks show potential for lightweight, ecological and low-cost construction.