Enhancement-type graphene treated cement-soil for building foundation improvement: experimental and microscopic investigations

This study investigates the mechanical performance and microstructural mechanisms of enhancement-type graphene (EtG) treated cement-soil mixtures for building foundation improvement. A series of unconfined compressive strength (UCS) tests, unconsolidated-undrained (UU) triaxial compression tests, and microstructural analyses, including scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) were conducted to evaluate the influence of EtG on strength, deformation, and microstructural changes. The optimal EtG content was determined to be 0.05 %, which increased UCS by 103.6 %, from 697 kPa (plain cement-soil) to 1052 kPa. The internal friction angle and cohesion also showed notable increases, reaching maximum values of 17.2° and 158 kPa, respectively, at the optimal EtG content. Microstructural analysis revealed that the addition of EtG enhanced the hydration reaction, promoting the formation of calcium silicate hydrate (C-S-H) and other gel products. SEM images indicated that EtG filled voids, refined pore structures, and created a denser matrix. Notably, EtG facilitated the formation of fibrous, rod-shaped, and needle-like hydrates, which improved particle bonding. EDS results confirmed the incorporation of EtG within the hydration products, with increased carbon content playing a critical role in enhancing the microstructure. XRD analysis highlighted the reduction in quartz peak intensity and the increased presence of hydrated calcium silicate gels, confirming the catalytic role of EtG in cement-soil composites. The findings demonstrate the potential of EtG as an effective nanomaterial for reinforcing cement-treated soils in building foundation applications, offering a sustainable approach to improving strength, durability, and microstructural integrity in ground improvement practices.