Performance of nano-modified soil–brick–cement: a machine learning and experimental study

Overburnt brick aggregate (OBBA) has lower strength and durability relative to natural stone aggregate (NSA). This study evaluates the impact of nano-chemicals on the characteristics of cement-stabilised OBBA base course layers. Mixtures SACN.25, SACN.5, SACN.75 and SACN1 containing 0.25 to 1 kg/m³ of nanocompounds, respectively, were used for surface treatment. Based on California bearing ratio and unconfined compressive strength testing results, SACN1 was ascertained as the optimal mixture. The X-ray diffraction analysis indicates that calcium-silicate-hydrate and kaolinite minerals enhance the strength and cohesiveness of the SACN1 mixture, respectively. Scanning electron microscopy analysis confirms that organosilane creates water-resistant alkyl siloxane layers, enhancing the durability of road surfaces. Flexural and durability testing confirm that SACN1 provides sufficient strength and resilience against environmental variations. Moreover, the SACN1 mixture complies with the standard values prescribed by India’s Ministry of Rural Development and the Indian Roads Congress requirements. Consequently, OBBA can serve as a substitute stone aggregate in road building when modified with nanochemicals. A Random Forest-based machine learning (ML) framework was employed to model the non-linear relationship between mix constituents and performance parameters and to perform multi-objective optimisation. The ML results successfully identified the optimal nano-modified mix that maximised strength and stiffness while minimising permeability, showing strong agreement with experimental observations.