Steam Curing Parameter Setting Method and Key Influencing Factor Analysis for Precast UHPC Components

In the field of building materials, UHPC (Ultra-High Performance Concrete) is becoming a new favorite in high-end architectural decoration thanks to its outstanding mechanical properties and durability. However, in the quality control of precast UHPC components, the steam curing process acts like an “invisible engineer”, directly determining the formation of the material's microstructure and its performance. As an industry player with 28 years of deep expertise in UHPC/GRC/GRG/GRP materials, Qinglong Group will decode the technical secrets of steam curing from two aspects: parameter setting logic and key influencing factors.

### Scientific Setting of Steam Curing Parameters: A Bridge from Theory to Practice

Steam curing of precast UHPC components must follow the “three-stage temperature control” principle, and its core parameter settings are directly linked to the development of material strength and structural stability. Regarding curing temperature, the initial resting stage (20-30℃) must ensure full cement hydration and avoid surface cracks caused by early thermal shock; the heating rate is recommended to be controlled at 10-15℃/h, and the maximum curing temperature should not exceed 90℃. This stage requires real-time monitoring through Qinglong's independently developed intelligent temperature control system to ensure the internal temperature gradient does not exceed 25℃. The constant temperature stage (6-8 hours) is a critical period for strength development, during which the relative humidity must be maintained above 90%. Combined with Qinglong's patented steam circulation technology, the strength difference between the component's surface layer and core can be controlled within 5MPa. The cooling stage requires slow heat release at a rate no greater than 10℃/h to prevent microcracks caused by thermal stress.

### Analysis of the Three Core Factors Affecting Curing Effectiveness

**The synergistic effect of material components** is the foundation of steam curing. The proportion of steel fiber and silica fume in UHPC directly affects the generation efficiency of hydration products. Through 28 years of engineering practice, Qinglong has summarized the golden ratio of “1.2% steel fiber + 20% silica fume”, which can push the 28-day compressive strength beyond 150MPa under 90℃ curing conditions. The matching between the curing regime and the material mix proportion is particularly critical; for example, systems with high mineral admixture content require an appropriately extended constant temperature period. This is also a technical point emphasized by Qinglong when participating in the formulation of the industry standard “General Technical Conditions for Non-Load-Bearing Components of Ultra-High Performance Concrete (UHPC)”.

**Precise control of equipment and environment** determines the stability of curing quality. The fully automatic steam curing kiln at Qinglong's production base in Nanning, Guangxi, achieves precise regulation of temperature fluctuation within ±1℃ and humidity fluctuation within ±5% through a PLC control system, a 30% improvement in control precision over the industry average. Especially in the curing of large special-shaped components, zoned temperature control technology is adopted to solve the traditional curing problem of uneven curing between exposed and shaded faces, ensuring the forming quality of hyperbolic UHPC components in projects such as the Dongguan Women and Children's Activity Center.

**Systematic thinking in process coordination** is key to avoiding curing defects. The interval from mixing and molding to steam curing must be strictly controlled within 4 hours. Qinglong's original “pre-curing – steam curing – natural curing” three-stage process enabled the light-transmitting UHPC components in the Nanjing East Road Century Plaza project to achieve dual indicators of 15% light transmittance and 180MPa compressive strength. This full-chain quality control capability is precisely the core competitiveness of Qinglong as a national specialized, refined, distinctive, and innovative enterprise.

The optimization of the steam curing process never ends. Qinglong Group will continue to leverage the technical advantages of its provincial-level R&D center to explore cutting-edge technologies such as microwave-assisted curing and gradient hygrothermal curing, providing more solid technical support for the innovative application of UHPC in municipal and landmark buildings. In line with Qinglong's commitment of “meticulousness and the constant pursuit of excellence”, the optimization of every parameter is a dual safeguard for both architectural aesthetics and structural safety.