Hydro-mechanical behaviour of alkali-activated binder treated soil

An experimental investigation on the mechanical improvement induced by alkali-activated binder based on the activation of a fluidal bed combustion fly ash on a clayey soil has been developed. The use of these binders for geotechnical applications is a promising issue in terms of sustainability since it reduces the carbon footprint and allows reusing secondary by-products such as artificial pozzolans. Treated samples were prepared by mixing soil and fly ash with water and alkaline solution and dynamically compacted. Mechanical behaviour has been investigated by means of triaxial tests performed on treated samples compacted at optimum water content. Addition of alkali activated binder increased stiffness and shear strength of treated samples, whose extent depends on binder content and curing time. Macroscopic behaviour of treated soil has been linked to the experimental evidences at microscale. Microstructural analyses highlighted a high reactivity of alkali-activated fly ashes as alumino-silicate source promoting the precipitation of new mineralogical phases with cementitious properties. Amorphous alumino-silicate gels produced from alkali-activation of fly ash bound particles aggregates leading to a decrease of cumulative pore volume and porosity of treated samples and modification of the modal pore size.