Development of multi-criteria optimisation framework for blended concrete systems: experimental study and global sensitivity analysis

Global warming and climate change have increased the demand for low carbon dioxide construction materials, as cement production accounts for nearly 8% of global carbon dioxide emissions. Supplementary cementitious materials (SCMs) provide a sustainable solution by reducing cement consumption and enhancing concrete durability. However, ultrafine SCMs such as silica fume (SF) can adversely affect workability and increase shrinkage, which are often overlooked in conventional mix design approaches focused primarily on strength and durability. A multi-criteria optimisation (MCO) framework for blended concrete that simultaneously considers fresh, mechanical, durability and shrinkage properties is proposed. Experimental investigations were conducted on concrete mixtures made with 20% fly ash (FA) and varying SF contents. The results showed that increasing the SF content enhanced strength and durability-related properties but reduced workability and increased shrinkage. Among the investigated mixtures, the concrete containing 20% FA and 10% SF exhibited the most balanced overall performance. To assess the robustness of the MCO framework, global sensitivity analysis was performed considering uncertainties in material properties and mixture proportions; the binder composition was identified as the dominant parameter influencing performance variability. The proposed MCO framework provides a robust and transferable decision making tool for designing balanced and sustainable SCM-based concrete mixtures.