Valorization of Fired Clay Bricks Debris (grog) Using Egg Shell and Coconut Shell in the Synthesis of an Ecological Compressed Earth Blocks: Microstructure and Engineering Properties

Abstract

The aim of this work is to valorize fired clay brick debris (grog, CH) by using egg and coconut shells in the production of eco-friendly compressed earth bricks for sustainable building materials. Samples were cured at ambient temperature (23 ± 3 °C) and prepared by varying different percentages of calcined eggshell (CO) and coconut shell (CN) at 13%, 26%, and 40%, respectively. Additionally, another mix design incorporated both calcined eggshell and coconut shell together into the grog powder. Comprehensive physico-mechanical properties such as water absorption (WA), bulk density (BD), apparent porosity (AP), moisture content (MC), compressive strength (σ), and elastic modulus (EM) were evaluated. Chemical composition, X-ray diffraction (XRD) analysis, Fourier-transform infrared spectroscopy (FTIR), Energy Dispersive X-ray (EDX) analysis, and Scanning Electron Microscopy (SEM) were also performed. Results show an increase in compressive strength with increasing percentages of calcined eggshell: for 87CH-13CO, 74CH-26CO, and 60CH-40CO, compressive strengths were 1.38, 2.70, and 3.88 MPa, respectively. For 87CH-13CN, 74CH-26CN, and 60CH-40CN, coconut shell addition similarly showed an increase in compressive strength. Bulk density decreased with increasing percentages of calcined eggshell and coconut shell as the percentage of grog decreased. Linear correlation equations between mechanical properties and mix proportions were determined. SEM micrographs revealed a dense microstructure with some agglomerations. These results indicate an improvement in engineering properties due to the addition of eggshell waste, making these enhanced properties suitable for sustainable eco-friendly building materials.