When Is the Best Time to Demold GRC Components? Key Influencing Factors and Practical Judgment Methods Explained

In the entire production process of GRC components, precise control of the demolding timing is like a conductor's baton in a symphony, directly determining the product's structural strength, surface texture, and production efficiency. As an industry participant with 28 years of deep expertise in UHPC/GRC/GRG/GRP materials, Qinglong Group will systematically analyze the scientific principles and practical implementation methods of GRC component demolding from three dimensions—material properties, process parameters, and hands-on experience—to provide replicable technical standards for the industry.

Core Criteria for Determining GRC Component Demolding Timing: The Dynamic Balance Between Strength and Form Stability

Demolding of GRC material (glass fiber reinforced concrete) is not simply a matter of time; it is a comprehensive reflection of the material's hydration reaction progress and structural load-bearing capacity. The industry typically uses compressive strength reaching 70% of the design value as the basic threshold. However, in Qinglong Group's production practice, we place greater emphasis on the “dual-indicator judgment method”—requiring both compressive strength ≥15MPa and surface hardness of at least Mohs hardness level 3. This standard prevents component deformation caused by premature demolding while also avoiding extended production cycles due to over-curing. In a cultural center project in Guangdong, this method raised the pass rate of GRC curtain wall components to 99.2%.

Five Key Influencing Factors: Full-Chain Control from Formulation to Environment

1. The Innate Determining Role of Material Formulation: Cement grade and glass fiber content directly affect the rate of strength development. Qinglong's self-developed C80-grade GRC formulation, incorporating 12% alkali-resistant glass fiber and composite mineral admixtures, increases early strength by 30% and shortens demolding time by 4 hours compared with traditional formulations.
2. Precise Regulation of the Curing Environment: In the constant-temperature, constant-humidity curing workshop at our Guangxi production base, we control the temperature at 20±2°C and humidity at ≥90%, combined with a gradient heating curve for steam curing (25°C→60°C→25°C) to ensure the hydration reaction proceeds uniformly.
3. Differentiated Treatment Based on Component Geometry: Flat-panel components with wall thickness ≤50mm can adopt an early demolding process, whereas double-curved irregular GRC components (maximum curvature radius 350mm), such as those in a Nanjing project, require curing extended to 72 hours, with embedded strain gauges monitoring internal stress changes.
4. Appropriate Selection of Mold Type: Steel molds have high thermal conductivity, which accelerates strength development and shortens demolding time by 20% compared with wooden molds. For GRG (glass fiber reinforced gypsum) components, due to the crystallization characteristics of gypsum, demolding can be carried out earlier—at a compressive strength of just 5MPa.
5. Dynamic Adjustment for Seasonal Climate: During winter construction, Qinglong employs an electric heat-tracing curing system, keeping the demolding cycle for northern projects stable within 48 hours—one day shorter than the industry average.

Three-Step Practical Judgment Method: Implementation Techniques from Laboratory to Production Line

1. Initial Judgment Stage: Combined Tactile and Visual Inspection
Press the component surface lightly with a finger—there should be no obvious indentation and the rebound should be quick; observe that the surface shows no water bleeding or dusting, with clear edges and corners. This stage can preliminarily rule out 30% of unqualified demolding timings.

2. Precise Judgment Stage: Tool-Assisted Quantitative Testing
Use a rebound hammer to check surface hardness (rebound value ≥35), combined with compressive strength tests on specimens cured under identical conditions. On Qinglong's digital production lines, specimen data is transmitted in real time through an IoT system, making demolding decisions scientific.

3. Final Judgment Stage: Experience Verification and Risk Pre-Control
For large GRC components (such as exterior wall cladding panels exceeding 10m²), a simulated load-bearing test at the lifting points is required to check for any microcracks. Over 28 years, Qinglong has built a database accumulated from 1,000+ projects and established demolding parameter models for different component types, keeping the first-time demolding pass rate stable above 98%.

Demolding is a critical node in GRC production, and its technical level directly reflects a company's process capabilities. Backed by the technical support of its national-level R&D center, Qinglong Group deeply integrates materials science with engineering practice. It has not only formulated the corporate standard “GRC Component Demolding Process Specification” but also participated in drafting the “Technical Standard for Building Application of Glass Fiber Reinforced Cement (GRC)” (JGJ/T423-2018). Looking ahead, with the wider adoption of UHPC/GRC composite components, we will continue to optimize demolding technology, providing more efficient and reliable solutions for the architectural decoration industry and fulfilling our corporate mission of “Creating Beautiful Architecture.”