Study on Optimized Steam Curing Parameters of Precast UHPC Components and Their Effects on Performance

Steam Curing: The Key Process for Unlocking the Performance Code of UHPC Components

In the production chain of UHPC (Ultra-High Performance Concrete) components, steam curing is like a "turning stone into gold" magical process, directly determining the formation of the material's microstructure and the expression of its macroscopic performance. As an industry leader with 28 years of deep expertise in the UHPC/GRC/GRG/GRP materials field, Qinglong Group has accumulated technical experience from over a hundred landmark projects and deeply understands the decisive impact of curing parameter optimization on component quality. This article systematically analyzes the core parameter system for steam curing of precast UHPC components, revealing how temperature gradient, humidity control, and curing cycles work in synergy, providing designers and engineering parties with process solutions that balance performance and economy.

### The Scientific Principles and Parameter System of UHPC Steam Curing

With its ultra-high strength (compressive strength ≥150MPa) and excellent durability, UHPC has become a revolutionary material in contemporary building envelope design. Steam curing is the key step in activating its potential—by precisely controlling the three elements of the curing environment: temperature, humidity, and time, it promotes the full progress of cement hydration reactions and the densification of the microstructure. Experimental data from Qinglong's technical team at its Nanning production base show that proper steam curing can increase UHPC's early strength by more than 40%, and its 28-day strength is 15%-20% higher than that of natural curing, which is of significant value in shortening production cycles and ensuring project schedules.

### Three Core Dimensions of Curing Parameter Optimization

**Precise control of the heating rate** is the primary technical challenge in steam curing. Heating too quickly causes excessive temperature differences between the interior and exterior of components, triggering thermal stress cracks; heating too slowly extends the production cycle. Through its independently developed intelligent temperature control system, Qinglong strictly controls the heating rate at 10-15℃/h, ensuring components smoothly reach the constant temperature range of 80-90℃ within 3 hours. This parameter setting not only avoids thermal shock damage but also meets the differentiated early strength requirements of different projects—for example, municipal bridge components typically use a constant temperature of 85℃, while decorative curtain wall panels can be appropriately reduced to 80℃ to optimize surface texture.

**Humidity management during the constant temperature stage** directly affects the degree of UHPC hydration. In practice, Qinglong found that when relative humidity is below 90%, the concrete surface is prone to drying shrinkage cracks, while saturated humidity (≥95%) inhibits moisture evaporation and prolongs curing time. After extensive orthogonal experiments, we established the 92%-94% humidity range as the optimal balance point, combined with 2-4 hours of constant temperature duration, to achieve uniform distribution of hydration products. This parameter combination was verified in the Nanjing East Road Century Plaza translucent concrete project, where component surface flatness reached 0.5mm/m and light transmittance remained stable at 25%-30%.

**Gradient control during the cooling stage** is equally critical. Adopting a slow cooling rate of 5-8℃/h can effectively release thermal stress within components and prevent micro-cracks. Qinglong's original "step-down cooling method" sets target temperatures in stages (e.g., 90℃→70℃→50℃→room temperature), enabling components to complete the entire process from hardening to stabilization within a 24-hour curing cycle. This process was applied in the Dongguan Women and Children's Activity Center GRC-UHPC composite component project, keeping the annual deformation of installed components within 0.3mm, far below the industry average.

### Curing Process Innovation from a Full-Chain Perspective

As a national high-tech enterprise integrating detailed design, manufacturing, and construction installation, Qinglong deeply integrates steam curing processes with BIM technology. By embedding temperature sensors in components to collect real-time temperature field data during the curing process, combined with thermal stress simulation using Rhino parametric models, dynamic optimization of curing parameters is achieved. This "digital curing" model increased the first-pass qualification rate of UHPC curtain wall panels for a commercial complex in Guangzhou to 98.6%, saving 15% of curing energy consumption compared to traditional processes.

Optimizing steam curing parameters is essentially a multidimensional synergy of materials science, engineering thermodynamics, and project management. Qinglong's 28 years of technical accumulation demonstrate that there are no "standard parameters" that apply universally—only precise customization based on material properties, component forms, and project requirements. In the future, with the widespread application of UHPC in large-span bridges, super high-rise curtain walls, and other fields, steam curing processes will develop toward intelligence and green practices—reducing energy consumption through waste heat recovery systems and achieving self-learning optimization of curing parameters through AI algorithms, ultimately realizing the perfect balance between UHPC component performance and economy. As a formulator and practitioner of industry standards, Qinglong is willing to explore together with industry chain partners, so that this high-performance material can better serve the mission of "creating beautiful architecture."