LOW CO₂ FOOTPRINT AND HIGH CIRCULAR CEMENTITIOUS BINDERS FOR BUILDING REHABILITATION BASED ON MINERALIZED RCF AND LF STEEL SLAGS UNDER SYNERGISTIC APPROACH

The carbon dioxide (CO₂) footprint reduction in conventional Portland cement production constitutes a huge challenge due to the limited availability of low carbon footprint and economic Supplementary Cementitious Materials (SCM) supplies to be employed in clinker substitution. This challenge increases when developing specific binders with a low carbon footprint for greener building rehabilitation due to the unique properties that these binders must meet, such as durability, compatibility, application flexibility and ease of use. A Carbon Capture and Utilization (CCU) approach based on mineralization by accelerated carbonation was applied to reduce sectorial carbon footprint and promote new circular building materials. In this work, a CO₂ sequestration was performed on different conditions to concrete fines (RCF) and ladle furnace (LF) steel slags wastes. The amount of CO₂ captured was calculated and the mineralogical transformation deeply studied and monitored by spectral tools (DRX, Raman, and Hyperspectral image HSI analysis), for process optimization. The effect of mineralization on new binders was assessed through the reactivity and accelerated pozzolanicity analysis. The obtained materials were synergistically employed as SCMin novel cementitious binders for building rehabilitation. As a result, relevant CO₂ capture (between50 and 117g eq. CO₂/kg by RCF and LF respectively) and lower clinker (K) content (<30%) by replacement yielded high circular low carbon footprint binders. The synergistically use of the obtained mineralized waste streams as SCM on new binders’ dosages, led to increase in pozzolanic phases generation. Carbonated RCF and LF wastes used as SCM in binders induced mechanical performance gains (achieving an increase in accelerated pozzolanic activity of 150%.) and lower environmental footprint (-27% CO₂, -270kg/t of binder) than a commercial binder.This research was funded by i) IHOBE, the public environmental management company of theBasque Government (Spain), Heidelberg Materials, and VOLBAS under NEUCLICEM project; ii)the Spanish Ministry of Science and Innovation (MICINN), the Spanish National Research Agency(AEI) and the European Regional Development Fund (ERDF), ref: PID2021-122390OB-C21(CIDECAR); and iii) the Basque Government [IT1619-22 SAREN research group].