Carbonated calcium silicates as pozzolanic supplementary cementitious materials

• Published in: Construction & building materials 2024-09, Vol.443, p.137764, Article 137764
• Main Authors: Cisiński, Michał, Biava, Giada, Winnefeld, Frank, Sadowski, Łukasz, Ben Haha, Mohsen, Zajac, Maciej
• Format: Article
• Language: English
• Subjects: Alumina silica gel; Compressive strength; Enforced Carbonation; Pozzolanic reaction
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2024.137764

This study examined the carbonation mechanisms and products of various precursors, including hydrated cement pastes and calcium silicate clinkers. Regardless of the materials investigated, all exhibited rapid carbonation reactions and achieved high degrees of carbonation. Calcium carbonate and siliceous gel were consistently formed as carbonation products. The starting materials significantly influenced the characteristics of the siliceous gel. Carbonated concrete pastes displayed a higher presence of alumina in the gel, resulting in greater surface area and nano-porosity compared to gels formed from calcium silicate clinkers. The pozzolanic reaction products also differed depending on the precursor, with carbonated concrete pastes forming C-S-H and AFm phases, while carbonated calcium silicate clinkers produced only C-S-H phase. Such variations impacted the evolution of mechanical performance in composite cements. Notably, carbonated composite cements containing recycled concrete pastes exhibited higher early compressive strength compared to carbonated calcium silicate clinkers. However, the final compressive strength is similar. •All samples showed rapid carbonation, forming calcium carbonate and siliceous gel.•Silica gel in carbonated pastes contain alumina and silica while the one in calcium silicate only silica.•Alumina silica gel from carbonated pastes had high surface area and nano-porosity.•Carbonated pastes and calcium silicates produce different products of pozzolanic reaction.•Carbonated pastes exhibit higher early compressive strength, but later strength is similar.