Multi-criteria Optimization of Sustainable High-strength LC3 Concrete Using an Integrated BWM-Taguchi Framework

The high carbon footprint associated with Ordinary Portland Cement (OPC) production necessitates the development of sustainable binder systems for structural concrete. Limestone calcined clay cement (LC3) offers a low-clinker alternative; however, achieving high-strength LC3 concrete remains challenging due to complex interactions among binder constituents, supplementary cementitious materials, and chemical admixtures. This study proposes an integrated multi-criteria optimization framework combining the Best–Worst Method (BWM) with the Taguchi experimental design to develop high-strength LC3 concrete while simultaneously satisfying strength and workability requirements. Three key mix-design parameters-binder proportion (OPC: LC2), ground granulated blast furnace slag (GGBS) content, and superplasticizer dosage were investigated using a Taguchi L9 orthogonal array, while BWM was employed to assign relative importance to selected performance criteria. The optimal mix (A 3 B 2 C 1 ), corresponding to an OPC: LC2 ratio of 70:30, 20% GGBS content (added as an additional supplementary binder component), and a superplasticizer dosage of 0.35%, achieved a 28-day compressive strength of 72.17 MPa, meeting the requirements for M60-grade concrete at a low water-to-binder ratio of 0.30 with adequate workability. Analysis of variance identified that binder proportion was the dominant factor governing overall performance. Microstructural investigations using SEM, EDS, XRD, and TGA indicated the development of a dense, hydrated matrix associated with clinker hydration, pozzolanic interaction, carbonate stabilization, and the progressive pozzolanic consumption of portlandite in the optimized LC3 concrete. The proposed BWM–Taguchi framework provides a systematic and robust approach for designing high-strength, comparatively low-clinker LC3 concrete with balanced multi-performance characteristics.