Mechanical properties of subgrade clay improved by a low carbon MgO-metakaolin binder

This research investigates the mechanical properties of subgrade clay enhanced by a low carbon cement: MgO-metakaolin binder, focusing on its efficacy in weak subgrade stabilisation under cyclic loading conditions. Soil samples were prepared and subjected to repeat load triaxial testing to evaluate their resilient modulus (Mr) and permanent deformation across various stress scenarios. Four distinct mixtures were analysed: untreated weak subgrade soil, soil with graphene, soil with MgO-metakaolin binder, and a combination of MgO-metakaolin binder and graphene. The results demonstrate that the samples with MgO-metakaolin binder achieved resilient modulus values up to 120 MPa, significantly enhancing both stiffness and deformation resistance. While the addition of graphene also improved soil performance, its effect was less pronounced compared with MgO-metakaolin binder. The combination of MgO-metakaolin binder and graphene produced promising results, indicating that graphene could provide supplementary benefits when used alongside MgO-metakaolin binder. This study highlights potential of low-carbon MgO-metakaolin binders as effective and sustainable stabilisers for weak subgrade soils. When combined with MgO-metakaolin binder, the addition of graphene could further enhance the binder by increasing thermal and electrical conductivity. These findings indicate that the proposed binder system can lead to more durable and environmentally friendly road infrastructure.