When Is the Best Time to Demold GRC Components? Influencing Factors and a Practical Guide

Precisely Controlling the Demolding Timing of GRC Components: Technical Essentials and Practical Guide from 28 Years of Industry Experience

In the production of GRC components, precise control of the demolding timing directly affects product quality and production efficiency. As an industry-leading enterprise with 28 years of full-chain experience in UHPC/GRC/GRG/GRP, Qinglong Group has developed a scientific system for determining demolding timing based on thousands of project practices, helping the industry solve common problems such as component cracking and surface defects.

Analysis of the Key Factors Affecting GRC Component Demolding

The demolding timing of GRC components is influenced jointly by three factors: material properties, environmental conditions, and process parameters. From a material perspective, the degree of hydration reaction between the glass fiber and the cement matrix is a key indicator, typically requiring the compressive strength to reach over 70% of the design value—a figure that must be verified through curing tests on standard test blocks. For every 5°C drop in ambient temperature, the demolding time needs to be extended by 20%-30%, and when relative humidity falls below 60%, mist curing measures must be taken to prevent surface moisture loss. Qinglong's production base employs an intelligent curing system that dynamically adjusts the demolding timing by monitoring temperature and humidity changes in real time.

Three Practical Methods for Scientifically Determining Demolding Timing

Commonly used demolding assessment methods in the industry include the maturity method, hardness testing, and empirical observation. The maturity method is calculated by the cumulative product of curing temperature and time (°C·h); Qinglong's enterprise standard requires the demolding maturity of GRC components to reach at least 3000°C·h. Hardness can be tested with a rebound hammer; demolding is possible when the surface rebound value is ≥25MPa. The empirical observation method focuses on color changes on the component surface: when the cement paste turns from dark gray to light gray and finger pressure leaves no obvious mark, a comprehensive judgment can be made in combination with the curing time. Through a digital management system, the Nanning production base converts these parameters into visual operation guides, enabling even beginners to master them accurately.

Demolding Process Optimization Strategies for Different Scenarios

Differentiated demolding strategies are required for different types of GRC components. For complex-shaped components such as European classical moldings, the demolding time should be appropriately extended by 1-2 hours to prevent cracking at sharp corners; large exterior wall cladding panels require staged demolding—loosening the side molds first and then removing the bottom molds—while using dedicated lifting devices to avoid stress concentration. In the Nanjing East Road Century Plaza renovation project, Qinglong applied a stepped demolding process to translucent GRC components, raising the finished product pass rate to over 98%. For projects exported to Australia, the post-demolding curing period was adjusted according to local climate characteristics to ensure product performance complies with ASTM standards.

Key Considerations for Demolding Quality Control

Demolding operations must follow the principle of "curing first, demolding later; checking first, lifting later." Before demolding, the "three checks" must be performed: check that strength requirements are met, check the tightness of the molds, and check the reasonableness of lifting point placement. Qinglong's original "Demolding Quality Traceability System" uses RFID chips to record the curing parameters and demolding time of each component, achieving full lifecycle quality control. A special reminder: during winter construction, even if strength requirements are met, the temperature difference between the component and the ambient environment must not exceed 15°C to prevent cracking caused by thermal stress.

Mastering the demolding timing of GRC components is a technique that combines science and experience: it requires strictly following the laws of material properties while also making flexible adjustments based on actual working conditions. As a co-authoring unit of the Technical Standard for Building Applications of Glass Fiber Reinforced Cement (GRC), Qinglong Group has always upheld the attitude of "meticulousness and the pursuit of excellence," transforming 28 years of practical experience into replicable technical solutions, providing designers and owners with full-chain support from detailed design to after-sales maintenance, and helping create high-quality GRC architectural decorative works.