Micro to nano-scale insights into a passive biomineralization pathway for developing a gate-to-gate carbon-negative bio-hybrid composite from lithium slag

Abstract

Abstract The urgent need to decarbonize concrete is hindered by the scarcity of conventional supplementary cementitious materials. Here, we report a novel, passive biomineralization pathway to transform lithium slag into a functional carbon‑negative bio‑hybrid composite for sustainable construction. Raw lithium slag was found to hold indigenous bacterial consortia, confirmed via microscopy, providing the biological premise for one‑year passive bio‑activation process under ambient environmental conditions. Native and recruited consortia colonized the slag surface, secreting organic acids that etched and dissolved aluminosilicate phases. The microbial weathering unlocked the latent pozzolanic reactivity of lithium slag through in‑situ precipitation of biogenic calcite within the weathered matrix. The resulting bioactivated lithium slag is thus a genuine bio‑hybrid composite, which sequestered approximately 13 kg of CO 2 per tonne of lithium slag, directly attributed to the biogenic calcite. At 60% cement replacement, the bioactivated lithium slag mortar achieved 93% of control’s compressive strength at 90 days, while 40% raw lithium slag achieved 89% of the control strength. Biominerlization of lithium slag enables a 20% higher cement replacement level. This work establishes a new paradigm for designing low‑carbon bio‑hybrid concrete composite by valorising an industrial waste stream through a near-zero operational energy biological process that simultaneously sequesters natural CO 2 . The integration of microbially mediated mineral synthesis within aluminosilicate matrix develops a new class of sustainable bio-composites that are both performance‑competitive and environmentally beneficial, advancing the principles of circular economy and green construction.