Ecotoxicological assessment of cement leachates from low-carbon cements in marine conditions

Developing low-carbon cementitious materials is essential for reducing greenhouse gas emissions in the construction sector, particularly for marine infrastructure dedicated to renewable marine energies. However, their potential ecotoxicological effects remain poorly documented. This study evaluated the chemical and biological effects of leachates from three cement types (CEM I, CEM III, and CEM V) under controlled saline conditions simulating seawater exposure. Leachates were chemically characterized using inductively coupled plasma optical emission spectrometry (ICP-OES), and their ecotoxicity was assessed using a multi-species approach that included sea urchin fertilization (Paracentrotus lividus), microalgal growth (Phaeodactylum tricornutum), bacterial bioluminescence (Aliivibrio fischeri), and microbial functional responses (growth, biofilm formation, and quorum sensing). A Toxicological Priority Index-based approach was used to integrate toxicity across biological endpoints. Targeted trace elements were not quantified under the analytical conditions used, whereas concentrations of major elements, including Ca, Al, Si, and K, varied with binder composition. However, the sensitivity of ICP-OES in the saline matrix did not allow the presence of trace elements at lower concentrations to be excluded. Despite these relatively moderate dissolved concentrations, all leachates induced measurable biological effects. CEM I exhibited the highest overall toxicity, strongly inhibiting sea urchin fertilization, microalgal growth, and bacterial activity. In contrast, CEM III and CEM V showed lower overall toxicity but more pronounced effects on specific microbial functions. These results indicate that toxicity cannot be directly inferred from trace-element concentrations and likely reflects a combination of physicochemical changes associated with cement dissolution, including pH, alkalinity, ionic composition, and potentially other dissolved constituents. Therefore, although low-carbon cements reduce CO₂ emissions, their distinct compositions can alter ecotoxicological profiles and, consequently, biological responses in marine environments. These findings highlight the importance of integrating ecotoxicological criteria into the evaluation of cementitious materials to support the development of more sustainable marine infrastructure.