Development of low-carbon engineered cementitious composites incorporating lithium slag: Mechanical properties, microstructure evolution, and life cycle assessment

The rapid expansion of the global lithium battery industry has led to a significant accumulation of hazardous lithium slag (LS), creating an urgent environmental challenge. This study develops a scalable cleaner production strategy by valorizing LS as a supplementary cementitious material in the fabrication of low-carbon engineered cementitious composites (ECC). The mechanical properties, microstructure evolution, and environmental-economic benefits of ECC mixtures with LS were evaluated. Experimental results indicate that the incorporation of LS significantly enhances the tensile strain of ECC, yielding a 47.57% increase in tensile strain capacity at a 20% replacement ratio. Microstructural analyses via MIP and SEM reveal that LS particles act as hydration nuclei and pore fillers, refining the pore structure (reducing harmful macropores by up to 60%) and optimizing the fiber-matrix interfacial properties. Although a trade-off in compressive strength was observed at higher replacement ratios, the flexural strength increased by 22.1% in the Li30 mixture. Furthermore, life cycle assessment (LCA) and cost-benefit analysis demonstrate that the optimized LS-ECC reduces the carbon intensity index by 8.18% and lowers material costs by 6.9% compared to conventional ECC. A final multi-objective optimization using Pareto frontier analysis identifies the optimal mix designs that balance mechanical resilience with eco-efficiency. This work provides a theoretical basis and practical guidelines for transforming hazardous lithium waste into high-performance, low-carbon construction materials, supporting circular economy goals in both the energy and construction sectors.