Valorization of waste concrete powder (WCP) through silica fume incorporation to enhance the reactivity and hydration characteristics

The aim of this study is to utilize the bulk proportion of waste concrete powder (WCP) as cementitious material in the fabrication of binder, and to investigate the impact of silica fume on the reactivity and hydration characteristics of thermomechanical activated WCP. A 29 Silicon Nuclear Magnetic Resonance (NMR) analysis confirmed the presence of reactive silica in the activated WCP. Various blends were prepared with a 50%-80% substitution of type CEM I 52.5 N cement. The combination of activated WCP and silica fume improved the reactivity of the binder blend and achieved a compressive strength comparable to cement. Mineralogical analysis revealed the development of secondary C-S-H gels in mixtures containing silica fumes and activated WCP, which is the result of a secondary hydration reaction between portlandite and reactive silica. The use of life cycle analysis software for the replacement of 60 wt % of cement with activated WCP was found to reduce carbon dioxide emissions by 80.42% due to the use of less cement, an environmentally friendly WCP activation process, even when considering the addition of 10% silica fume. This innovative approach not only enhances WCP reactivity and mechanical strength but also significantly contributes to the reduction of carbon emissions. By elucidating the formation mechanisms and environmental benefits, this study paves the way for a more ecoconscious and efficient construction methodology, promoting the vision of a greener future.