Multi objective optimization of novel ultra-green high performance LC3 concrete incorporating geopolymer cold-bonded lightweight artificial aggregates using central composite design based response surface methodology

The cement industry contributes approximately 8 % of global CO₂ emissions with escalating environmental pressures demanding urgent innovation toward carbon-neutral construction materials. While limestone calcined clay cement (LC3) technology and geopolymer cold-bonded lightweight aggregates have individually demonstrated significant potential for sustainable construction applications, no systematic investigation has explored their synergistic integration to harness combined environmental and performance benefits. This study developed and optimized LC3 concrete incorporating developed geopolymer cold-bonded lightweight aggregates (GCLA) through comprehensive two-phase multi-objective optimization employing Central Composite Design-based Response Surface Methodology. In Phase I, optimization of GCLA achieved exceptional 0.847 composite desirability with 40.2 MPa bulk crushing strength representing significant improvement over conventional aggregates while maintaining density < 1200 kg/m³ and superior 2.3 % water absorption. In Phase II, LC3-GCLA concrete optimization yielded remarkable 0.923 composite desirability through optimal 58.4 % GCLA replacement and 11.2 % recycled cement content, achieving 71.2 MPa compressive strength with 22 % density reduction. Response surface models demonstrated superior predictive capability with R² values 0.953–0.977 and validation errors < 5 %. Life Cycle Assessment quantified exceptional environmental performance with 57 % global warming potential reduction (165 vs 385 kg CO₂-eq/m³). This study establishes the first systematic framework for LC3-GCLA integration, demonstrating that novel design of sustainable concrete technology can simultaneously achieve high-performance structural requirements while significantly reducing environmental impact through innovative waste valorization and multi-objective optimization methodologies.