Potential of carbonated industrial by-products in the synthesis of green construction materials

Abstract

Carbonated steel slags have been proposed as a potential precursor in alkali-activated materials, due to their ability to both utilize industrial by-products and store CO2. However, the influence of carbonation on the reactivity and performance of steel slags in alkali-activated systems remains largely unexplored. This thesis investigates the use of carbonated Petrit T (CPT), a by-product from sponge iron production, as a co-binder in alkali-activated materials. Blast furnace slag was used as the primary binder, and was replaced with different mass ratios of CPT. The resulting materials were evaluated with respect to reaction kinetics, phase formation, porosity, microstructure and mechanical performance. The materials were evaluated in terms of setting time, heat evolution during reaction, phase development, molecular structure, surface area, microstructure, elemental composition and compressive strength. The results showed that CPT influenced the reaction behavior of the systems. Low CPT content accelerated the initial setting behavior, while higher replacement levels delayed later reaction stages and reduced mechanical performance. TGA and FTIR analyses confirmed the formation of C–A–S–H gel phases in all alkali-activated samples. They also showed that the carbonate related phases were present after alkali activation and increased with increasing CPT content. BET analysis showed that pore volume and specific surface area increased with increasing CPT content, indicating the formation of a more porous microstructure. SEM/EDS observations revealed the presence of unreacted BFS and CPT particles, suggesting limited participation in gel formation. Overall, the results indicate that carbonated steel slags can be incorporated into AAMs and contribute to CO2 storage through mineral carbonation. However, at the investigated replacement levels, CPT behaved more as an inert filler and negatively impacted the mechanical performance of the materials.