Steam Curing Parameter Settings for Precast UHPC Components: Precise Control of Temperature, Humidity and Time

Steam curing is the key process for precast UHPC components to achieve high strength and high density, and its parameter settings (temperature, humidity, time) must be scientifically matched to material properties and component types. As a participating unit in formulating the UHPC industry standard, Qinglong has drawn on 28 years of curing experience to establish an intelligent curing system, achieving consistently improved component performance in projects such as Shanghai New World and Yangshengtang Pharmaceutical.

The core of parameter control during the heating stage is to avoid thermal stress cracking. Qinglong adopts a gradient heating strategy, controlling the initial heating rate at 5-10℃/h; when the temperature rises to 40-50℃, it is held for 2-3 hours to allow moisture inside the UHPC to distribute evenly, before heating continues to the target temperature. An excessively fast heating rate will cause the temperature difference between the interior and exterior of a component to exceed 25℃, triggering microcracks. Especially for thin-walled components (thickness ≤30mm), the heating rate must be strictly controlled within 5℃/h. In the 50mm-thick UHPC openwork panel project for the Ouargla Hotel in Algeria, Qinglong effectively eliminated the risk of cracking at the openwork areas through gradient heating, ensuring component integrity.

The parameters of the constant-temperature stage directly determine strength and density, making it the core step of curing. Qinglong sets constant-temperature parameters according to component type and thickness: for standard components (thickness 30-50mm), the constant temperature is 90-95℃ for 12-16 hours; for thick-plate components (thickness ≥60mm) or load-bearing components, the constant temperature is raised to 95-100℃ and the duration extended to 16-24 hours. Humidity during the constant-temperature stage must be maintained at ≥95% to ensure full cement hydration and prevent surface water loss and sanding. Qinglong's intelligent curing kiln monitors temperature and humidity in real time with deviations of ≤±2℃/±5%. In the Shanghai Astronomy Museum project featuring UHPC sculptures over 3 meters tall, 20 hours of constant-temperature curing delivered a 28-day compressive strength exceeding 160MPa, far surpassing design requirements.

Parameter control during the cooling stage must prevent secondary cracking. Qinglong adopts a slow cooling strategy with a cooling rate of ≤8℃/h; when the component temperature drops to 10-15℃ above ambient temperature, cooling stops and the components dissipate heat naturally to room temperature. For components with complex shapes or embedded parts, the cooling rate must be further reduced to 5℃/h to prevent interfacial cracks caused by differences in the coefficients of thermal expansion between the embedded parts and the UHPC matrix. In the shaped UHPC component project—covering U-shaped panels, inclined slabs and other special shapes—for the Yirui Biotechnology Building in Shenzhen, slow cooling allowed internal and external stresses to release evenly, with no cracking whatsoever and surface flatness deviations of ≤±1mm.

Adaptive adjustment of curing parameters is Qinglong's core technical advantage. For different cementitious material systems and fiber types, Qinglong optimizes parameters through preliminary trials. For example, for UHPC components with added steel fibers, the constant-temperature duration can be shortened by 2-3 hours; for artistic shaped components, in order to preserve surface texture, the constant temperature is appropriately lowered (85-90℃) while the duration is extended. Qinglong's curing parameter settings not only comply with the industry standard "General Technical Conditions for Non-Load-Bearing Ultra-High Performance Concrete (UHPC) Components" but are also flexibly adjusted to actual project requirements, ensuring stable performance for every batch of components. For precast UHPC component production, scientifically set steam curing parameters are the key to quality assurance. With intelligent curing equipment and extensive practical experience, Qinglong provides reliable process support for projects.