Indicator-based sustainability assessment of poultry litter ash (PLA) as a supplementary cementitious material using an AHP-TOPSIS-RSM framework.

The decarbonization of cementitious materials requires valorizing locally available waste streams while maintaining balanced mechanical, environmental and economic performance. Poultry litter ash (PLA), a biomass-derived residue, has shown potential as a supplementary cementitious material; nonetheless, its integrated sustainability performance remains insufficiently explored. This study evaluated binary PLA-cement mortars through a combined experimental and multi-criteria decision framework. PLA calcined at 600-800 °C was incorporated at 10-20 wt% cement replacement, and compressive strength (3-90 days), cradle-to-gate CO2-emissions, and production costs were assessed per functional unit of 1 m3 mortar. AHP-TOPSIS was used to rank blends, and CCD-RSM was applied for optimization and validation. Results indicate that 10 wt% PLA calcined ay 600 °C increased 28-days compressive strength by up to 26.7% while reducing CO2-emissions by 4-9% and costs by 6-13% relative to the reference mortar. Higher replacement ratios caused dilution effects and weaker interfacial transition zones, limiting long-term performance. Multi-criteria ranking consistently identified the 10 wt% threshold as optimal. The integrated TOPSIS-RSM framework provides a transferable methodology for balancing mechanical enhancement with moderate environmental and economic advantages, aiding decision-support tools for sustainable mortar design, directly contributing to SDGs 9, 11, 12, and 13.