Valorization of palm kernel shell waste in fired clay bricks: Multi-scale characterization and sustainable applications

This study investigates the effects of palm kernel shell powder as a bio-additive in clay bricks fired at 900°C a firing temperature representative of industrial practice in Central and West Africa and specifically recommended for Cameroonian clays. Bricks incorporating varying PKS dosages (0-60%) were analyzed for their physicochemical and thermomechanical properties. Results show that PKS addition reduces density but increases loss on ignition, water absorption, and linear shrinkage. Mechanical strength decreases significantly with higher PKS content, limiting structural applications to ≤25% PKS, while higher contents (>35%) show potential for thermal insulation due to enhanced porosity. Regarding the bricks' chemical properties, scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) mapping identified the various atoms present in each sample (C, O, Mg, Fe, Si, Al, Na, K, and Ti). Furthermore, FTIR (Fourier transform infrared spectroscopy) and XRD (X-ray diffraction) confirmed the crystalline nature of kaolinite and revealed the amorphous structure of the shell powder in the material after heating it to 900°C. These findings were corroborated by TGA, DTA, and DTG analyses. Regarding mechanical properties, the compressive and flexural strengths of bricks fired at 900°C and containing the bio-additive decreased significantly with increasing palm kernel shell powder content in the composite. An optimal compromise was identified at 25 wt% PKS, yielding a lightweight brick (970.90 kg/m 3 ) with a compressive strength of 5.8 MPa, suitable for non-loadbearing applications while reducing raw clay consumption by one quarter.