Accelerating the strength development of castables at 10 °C via introducing prehydrated CAC

The strength development of CAC-bonded castables at low ambient temperatures is of low speed, leading to extended curing time and reduced production efficiency for the castable factories at the winter time. Traditional accelerating agents primarily work by enhancing cement dissolution to speed up hydration. Recent studies suggest that certain nanoparticles can also facilitate hydration by accelerating the nucleation and growth of hydration products. This study proposes to prepare nanoscale hydration products by prehydration of CAC suspension at 10 °C, which is then added to CAC-bonded castables acting as nucleation seeds to accelerate the hydration of CAC, thereby speeding up the development of mechanical properties of castables. The results show that nanoscale hydrates CAH 10 and AH 3 form on the surface of prehydrated CAC particles in the suspensions. The suspension prehydrated for 4 h most significantly enhances the early strength of castables, as the quantity and size of the hydrates reach an optimal state. Additionally, the incorporation of prehydrated CAC suspensions has a slight negative impact on the mechanical properties after heat treatment at 800 °C and 1100 °C, but has little effect on the mechanical properties of castables after calcination at 1450 °C. This method could effectively improve the production efficiency of castables without using special agents with the added benefit of increased resource utilization rate.