Cementless ultra-high performance concrete (UHPC) using CaO- activated GGBFS and calcium formate as an accelerator

This study proposes an innovative approach to develop cementless ultra-high performance con-crete (UHPC) by activating ground granulated blast furnace slag (GGBFS) without an alkaline-activating solution. To develop cementless UHPC, calcium oxide (CaO) (5% by weight) was used to activate GGBFS, and calcium formate (CF) was used as an accelerator at concentrations rang -ing from 0 to 6 wt%. The results showed that CF significantly improved the mechanical proper -ties until 5 wt% and all the samples, including CF, exhibited a compressive strength of over 150 MPa. Uniaxial tensile tests revealed strain-hardening behavior, similar to typical cement-based UHPC. The addition of CF led to an increase in hydration products and pore size refine-ment, resulting in improved mechanical properties. The life cycle assessment results indicated that the developed UHPC mixture had nearly 70% lower CO2 emission than cement-based UHPC. The experimental results highlight the potential of this method for sustainable UHPC develop-ment.