Mechanochemical pre-treatment of recycled concrete fines for enhanced carbon capture and performance in FLG-integrated LC3 blends

Scaling up waste concrete recycling offers a viable pathway to decarbonisation of the cement industry. Recycled concrete fines (RCF), a significant component of recycled concrete, show favourable carbonation reactivity due to the presence of cement hydrates. However, their increased porosity and microcracks along with reduced cementing efficiency, limits their effective cement replacement level and practical performance. This study uses mechanochemical pre-conditioning to enhance the carbonation capacity and reactivity of RCF as a limestone and pozzolan source for limestone calcined clay cement (LC 3 ). The impact of few-layer graphene (FLG), produced through liquid phase exfoliation, on improving the LC 3 systems’ properties to compensate for the strength loss due to the RCF addition is also examined. The results show that mechanochemical activation is an efficient technology for significantly enhancing RCF's performance and particularly improving its carbon capture capacity by approximately 50% with NaOH assistance. New supplementary cementitious materials (SCMs) can be developed with an optimum pozzolan to limestone ratio of 2 from sustainable sources for LC 3 cement. This study explores the integration of mechanochemically activated RCF with FLG in an LC 3 system, demonstrating a promising 10% increase in compressive strength and highlighting the potential of this approach for enhancing the performance of recycled materials in low-carbon cement systems. • ⁠NaOH-assisted MCA increased CO₂ uptake by ∼50% via mechano-chemical effects. • Few-layer graphene delivered 45% higher early and 10% overall strength. • Single recycled stream enabled LC 3 at optimal 1:2 limestone–pozzolan ratio. • MCA caused RCF to act as dual-source limestone–pozzolan in LC 3 , boosting CO₂ uptake.