Recycled lithium slag powder for foam concrete: A durability assessment

The rapid growth of the lithium battery industry generates vast quantities of lithium slag, posing significant environmental and disposal challenges. This study explored the use of recycled lithium slag powder (RLSP) to partially replace Portland cement in foamed concrete, providing research support for the resource utilization pathways of lithium slag as an auxiliary cementitious material. Six types of lithium slag powder foamed concrete (LSFC) were prepared with RLSP dosages ranging from 0 % to 50 % by cement mass. The mechanical properties and durability of LSFC were evaluated through compressive strength at 7 and 28 days, as well as mass loss rate and strength damage after dry-wet and freeze-thaw cycles. Advanced analytical methods namely X-ray computed tomography (X-CT), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to investigate pore architecture, microstructural features, and hydration processes. Experimental results showed an almost linear decrease in compressive strength with increasing RLSP content; the 28-day strength failed to meet standard requirements when RLSP exceeded 40 %. X-CT analysis revealed that RLSP incorporation led to pore structure degradation, with worsening pore size distribution, sphericity, and fractal dimension, all directly correlated with reduced performance. This degradation is attributed to the insufficient cementitious activity of RLSP and the adverse effects of excessive gypsum and inert particles on bubble stability, resulting in increased porosity and the formation of larger, more complex pores.Although RLSP reduces durability, when the dosage does not exceed 20 %, the durability performance of the specimen still meets relevant standards and satisfies actual engineering needs. X-CT characterization further confirmed that pore structure degradation was the primary cause of performance decline under durability cycles. This study provides essential experimental support for using RLSP as an auxiliary cementitious material to partially replace cement in foamed concrete. The durability research offers technical reference for broader engineering applications of LSFC, such as in roadbed with high durability requirements.