Maximising the utilisation of WGP in seawater-mixed UHPC

Using high-volume reactive binders and superplasticisers in ultra-high-performance concrete (UHPC) would be costly, resulting in poor workability and high autogenous shrinkage. Using seawater for UHPC production could magnify these issues. This study incorporated a high waste glass powder (WGP) content in seawater UHPC to reduce the reactive binder and superplasticiser dosages. Through the combined effects of seawater and WGP, a self-compacting seawater UHPC was developed with a compressive strength of 140 MPa and a reduced autogenous shrinkage of approximately one-third of the reference. The self-compactibility and reduction of the stickiness of the UHPC were achieved because of reduced plastic viscosity, which was contributed by a high zeta potential of WGP and lower yield stress due to the hydrophobic surface of WGP. In addition, the mechanical performance of the seawater UHPC incorporating high-volume WGP could be maintained at least 120 MPa because of minimising trapped air and porosity by reducing the plastic viscosity, enhancing reactivity of WGP and SF and achieving a higher polymerisation degree (PD) and longer mean chain length (MCL) of C-S-H. The reduced autogenous shrinkage was attributed to replacing binders with a higher reactivity by WGP, which resulted in fewer fine pores and reduced shrinkage in the microstructure.