How to Set Steam Curing Parameters for Precast UHPC Components?

Steam curing parameters for precast UHPC components must be scientifically set across three stages—heating, constant temperature, and cooling—with core control of temperature (80-90℃), humidity (≥90%), and curing time (48-72 hours). Qinglong precisely regulates these parameters through its intelligent curing system, ensuring components reach over 80% of design strength at 7 days, with density and durability improved simultaneously, meeting the production needs of major projects such as the Yangshengtang Hangzhou Industrial Park and Shanghai New World Plaza.

1. Heating Stage: Slow Heating to Avoid Thermal Difference Cracks

The core of the heating stage is controlling the heating rate to prevent cracking caused by excessive temperature difference between the interior and exterior of components. Parameter settings: heating rate of 10-15℃/h, taking 5-8 hours to rise from room temperature to the target temperature (80-90℃); rapid heating is strictly prohibited. Temperature control: the starting temperature should not be below 15℃; if the ambient temperature is below 5℃, the curing room must be preheated to above 15℃ before components are placed inside. Humidity requirements: humidify synchronously during heating, keeping humidity at 80%-90% to avoid rapid evaporation of moisture from component surfaces. Qinglong technology: the intelligent curing room is equipped with temperature sensors (accuracy ±1℃) to monitor component interior and ambient temperatures in real time and automatically adjust the heating rate. On one project, the temperature difference during the heating stage was controlled within 10℃, with no cracks.

2. Constant Temperature Stage: Precise Temperature Control to Promote Full Hydration

The constant temperature stage is key to improving UHPC strength and density, and parameters must strictly match material characteristics. Temperature settings: 80-85℃ for standard components, and up to 85-90℃ for high-strength components (compressive strength ≥150MPa); constant temperature duration of 48-72 hours. Qinglong's standard UHPC is held at constant temperature for 48 hours, achieving a 7-day compressive strength of 140MPa. Humidity control: humidity ≥90%, preferably saturated steam curing, ensuring component surfaces remain constantly moist to promote full hydration of cementitious materials. Qinglong's curing room humidity sensors have an accuracy of ±2%, continuously maintaining a saturated humidity environment. Special requirements: for hollow and thin-walled components (thickness ≤20mm), the constant temperature is lowered by 5-10℃ and the duration extended by 12 hours to prevent surface sanding caused by high temperature. Qinglong's 20mm-thick hollow panels for the Ouargla Hotel in Algeria were held at a constant temperature of 80℃ for 60 hours.

3. Cooling Stage: Smooth Cooling to Ensure Structural Stability

The cooling stage requires controlling the cooling rate to avoid internal stress caused by thermal expansion and contraction. Parameter settings: cooling rate ≤10℃/h, taking 6-10 hours to drop from the constant temperature to room temperature; natural cooling or forced cooling is strictly prohibited. End-point control: the curing room may only be opened when the temperature has dropped to within 20℃ of the ambient temperature; if the temperature difference is too large, insulation must be maintained for a slower descent. On one Qinglong project, the door was opened when the temperature dropped to 30℃ (ambient temperature 25℃), and the components showed no shrinkage cracks. Subsequent curing: after cooling, remove the components and continue curing covered with moisture-retaining film for 3-5 days to ensure the hydration reaction continues. Qinglong components that receive 5 days of moist curing after steam curing achieve a 28-day strength 10%-15% higher than steam curing alone. System assurance: Qinglong's intelligent curing system can preset curing curves and automatically complete the entire heating, constant temperature, and cooling process, recording curing data for each batch with 100% traceability.