Utilization of eggshell food waste to mitigate geotechnical vulnerabilities of fat clay: a micro–macro-investigation

This study explores the potential of using eggshell food waste by valorizing it through calcination in the form of eggshell powder (ESP) to mitigate the geotechnical vulnerabilities of the fat clay. The physical, mechanical, volumetric change and micro-stabilization responses of treated soil samples were examined considering varying ESP content and curing periods (kc). The present study observed a 62% and 17% decrease in the plasticity index (PI) and liquid limit (LL) of the fat clay with 10% ESP content, respectively. Meanwhile, a significant increase was noted in unconfined compressive strength (qu), elastic modulus (E50), and California bearing ratio (CBR) with the augmentation of ESP in the fat clay. Furthermore, the increase in strength parameters became much more prominent when samples were subjected to prolonged kc. In addition, the ESP-treated fat clay conspicuously demonstrated a reduced deformation, swelling potential and compressibility due to the formation of a hardened soil skeleton. Moreover, the optimal dosage of ESP for the selected soil was established to be 10% as it was observed that the strength and compressibility responses improved significantly up to this ESP concentration in soil, while beyond this threshold, any further improvement in these properties almost ceased. Furthermore, the mineralogical and microstructural analyses revealed the formation of cementitious content in fat clay, namely the hydrates of calcium silicate (CSH) and calcium aluminate (CAH), resulting from a pozzolanic reaction between the silica and calcium oxide present in the fat clay and the calcined ESP, respectively.