How to Set Steam Curing Parameters for Precast UHPC Components?

Steam curing is a key process for the strength development of UHPC components, and parameter settings directly affect the final product performance. Based on 28 years of process data, Qinglong Group holds that the steam curing of quality UHPC should follow the principle of "slow heating, sufficient constant-temperature holding, and gradual cooling," with specific parameters dynamically adjusted according to component thickness, mix proportions, and environmental conditions. A standard curing regime typically consists of: a heating rate of 10-15℃/h, a constant temperature of 60±5℃, a holding time of 24-48h, and a cooling rate of ≤15℃/h.

The heating stage must be controlled smoothly to avoid microcracks caused by thermal stress. In the Shenzhen Yirui Biotechnology Building project, Qinglong Group precisely controlled the heating rate through a PLC system: 15℃/h was used for components under 20mm thick, reduced to 10℃/h for mass components (thickness >50mm). A rest period of 1-2 hours before heating allows the internal temperature of the components to become uniform. Temperature sensors are arranged at the center and on the surface of the components, with the temperature difference controlled within 20℃ to prevent excessive temperature gradients.

The constant-temperature stage is critical for strength development. The holding temperature is determined by the cement type: 70-80℃ for sulphoaluminate cement systems and 60-70℃ for Portland cement systems. In its Algeria hotel project, Qinglong Group determined through testing that the optimal holding time is plate thickness (mm) × 0.5 hours, ensuring full hydration of the core. Humidity is kept above 95% to prevent surface moisture loss. Monitoring data shows that scientific constant-temperature curing enables the 3-day strength of UHPC to reach over 70% of its 28-day strength.

The cooling stage must proceed slowly to prevent shrinkage cracks. The cooling rate is controlled at 10-15℃/h, and curing ends when the temperature difference with the environment is no greater than 20℃. For thick, large components, Qinglong Group adopts stepped cooling, with a temperature difference of no more than 10℃ per stage and 2 hours of thermal insulation at each stage. After curing, components must continue curing for 3 days in a 20℃ environment to complete strength stabilization. This refined control of curing parameters ensures the stability and consistency of UHPC component performance.