Geotechnical characteristics of clayey soil stabilized with fly ash and marble dust

This study investigates the separate and combined impacts of Class-F fly ash (FA) and marble dust (MD) on the geotechnical properties and resilient modulus $\left(M_R\right)$ of clayey soil. An intensive series of laboratory tests, including plasticity, swelling-shrinkage, compaction, unconfined compressive strength ($\mathrm{UCS}$), shear strength, California Bearing Ratio ($\mathrm{CBR}$), cyclic triaxial, and microstructural analyses, were conducted on soil specimens containing FA and MD at different percentages varying from 0 % to 12 %. The results showed that FA and MD additions significantly reduced the plasticity, free swell, and linear shrinkage potential of the soil, whilst $\mathrm{UCS}$ and $\mathrm{CBR}$ values increased up to a threshold value of 6 % to 9 % and then declined. The incorporation of FA, MD, and their combination (FA + MD) enhanced the soil’s $\mathrm{CBR}$ by approximately 45.1 %, 55.9 %, and 85.1 %, respectively. Similarly, the $\mathrm{UCS}$ of the soil cured for 7 days improved by 14.1 %, 44.0 %, and 72.5 %, respectively. The cyclic triaxial tests yielded the highest $M_R$ values with FA alone, leading to a 51.1 % increase. When FA and MD were used together, $M_R$ values increased by 31.6 %, which was relatively higher than the 28.1 % increase observed with the use of MD alone. Furthermore, statistical modeling to predict the $M_R$ values was proposed, evaluated comparatively with already available applications, and hereby confirmed its superiority over traditional models to save time for future researchers.