Tailored copper-based ionic liquids as multifunctional admixtures for cementitious materials

Microbial colonization accelerates the degradation of cementitious infrastructure, while many antimicrobial additives suffer from aggregation, leaching, or performance trade-offs, creating demand for multifunctional, low-dosage admixtures. This study presents the design, synthesis, and pioneering application of novel chlorocuprate ionic liquids ([bmim]Cl–CuCl₂ ILs) as functional and sustainable admixtures for cementitious materials. By systematically varying the CuCl₂ molar fraction (χ_CuCl2 = 0.15–0.33), we tailored the physicochemical properties of these ILs and incorporated them into CEM I and CEM II systems at different dosages ranging from 0.125 to 0.50 wt%. The admixtures accelerated hydration and enabled substantial setting-time reduction in CEM II, where the initial/final setting times decreased from 208/261 min to 102/180 min at 0.50 wt% and χ_CuCl2 = 0.33. At an optimized intermediate dosage (0.25 wt%), mechanical performance was maintained or improved; for CEM I, compressive strength reached 59.5 MPa and flexural strength 9.9 MPa at 28 days (χ_CuCl2 = 0.25). The ILs exhibited intrinsic antimicrobial activity with MIC (microbiologically induced corrosion) values in the range 31.25–500 mg/L, with the best performance against P. aeruginosa (MIC = 31.25 mg/L for χ_CuCl2 = 0.25). Importantly, antimicrobial functionality was retained in the cement matrix: for CEM I composites, microbial purity improved markedly (OD₆₀₀ reduced from 0.133 to 0.001–0.004, with bacterial counts below detection for most formulations). This study pioneers the use of a novel class of metal-coordinated ILs in cement science, offering a functional and eco-friendly solution that supports the advancement of sustainable construction practices.