Role of carbide slag in the preparation of low-clinker cement: Insight into hydration kinetics and microstructure

The potential to reduce clinker content in LC3 cement to up to 50% and below is promising, thanks to the synergistic effects of its constituents. However, lower clinker content can lead to challenges such as reduced pH due to significant consumption of precipitated CH, which may compromise durability and mechanical performance. Addressing these issues, we explore the use of carbide slag as an additional source of calcium hydroxide (CH) in LC3 with a clinker factor of 50% and below 50%. In overall, the addition of carbide slag produced positive results with a significant retainment of strength similar to reference LC3-50. It was observed that part of the extra CH from carbide slag was consumed during the hydration in LC3-50. The optimized content of 8% CH in LC3- 50-8CH gained significantly higher early strength than the reference LC3-50 at early age and later age, which was attributed to improved pozzolanic reaction degree of calcined clay. Further reduction in clinker content to 40% in LC3-40 could achieve a similar strength at LC3-50 at 28 days. However, the hydration degree of C3S and C2S was reduced with the addition of CH at low clinker content below 50%.