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

In the entire production process of GRC components, precise control of the demolding timing is like a conductor's baton in a symphony—too early can easily cause structural damage, while too late may lead to mold adhesion and surface quality defects. As an industry player with 28 years of deep expertise in UHPC/GRC/GRG/GRP materials, Qinglong Group has drawn on practical experience from thousands of projects to develop a scientific system for determining demolding timing, helping industry practitioners avoid more than 90% of early-stage quality risks.

I. The Golden Time Window for GRC Component Demolding: Dynamic Balance from Material Properties to Environmental Variables

The demolding timing of GRC components is not a simple matter of time, but the result of the combined effect of material strength development and process conditions. Laboratory data shows that under standard conditions with a curing temperature of 20±2℃ and relative humidity ≥90%, ordinary GRC components typically reach the demolding strength threshold (≥7MPa) 12-24 hours after casting, but this benchmark must be dynamically adjusted according to three core factors. Qinglong's production base uses an intelligent curing system to monitor real-time changes in the internal temperature field of components, combined with the Maturity Method to accurately calculate strength development curves, ensuring that the demolding timing matches the actual strength of the components.

II. Analysis of Key Influencing Factors: Four Dimensions Determine Demolding Success

1. Material Ratio and Fiber Characteristics: The glass fiber content (usually 4-5% by volume) and length (generally 6-12mm) directly affect early strength development. In Qinglong's crack-resistant formula, the addition of nano-scale silica fume and ultra-fine mineral powder increases the early strength of GRC components by 30% under the same curing conditions, effectively shortening the demolding cycle.

2. Curing Environment Parameters: For every 5℃ decrease in temperature, the demolding time needs to be extended by 20-30%; when humidity falls below 80%, surface moisture evaporates too quickly, easily producing shrinkage cracks. In the Harbin Ice and Snow World project, Qinglong adopted steam curing combined with electric heat tracing technology, compressing the winter demolding time from the conventional 72 hours to 36 hours, while ensuring a surface flatness error of ≤2mm.

3. Component Geometric Features: Irregular components (such as double-curved curtain wall panels) and thin-walled components (thickness <10mm) require the “segmented demolding method”. Taking the hollow carved GRC components of a cultural center in Guangzhou as an example, Qinglong's technical team used finite element simulation to identify stress concentration areas and implemented a step-by-step demolding plan—side molds first, then the bottom mold—successfully avoiding the deformation problems caused by traditional one-time demolding.

4. Mold Type and Surface Treatment: Steel mold surfaces need to be coated with a special release agent (silicone-based or wax-based), while wooden molds require sealing treatment. Qinglong's self-developed water-based release agent achieved 50 consecutive demoldings without residue in the Shenzhen International Convention and Exhibition Center project, reducing process costs by 15% compared with traditional oil-based release agents.

III. Practical Operation Guide: A Standardized Process from Testing to Execution

1. Strength Testing Methods: Use dual verification with a rebound tester and compressive testing of specimen cubes; the on-site rebound value must be ≥25MPa (equivalent to 7MPa compressive strength), while also reserving same-condition cured specimens for failure load testing. Qinglong's Nanning production base is equipped with fully automatic compression testing machines to ensure that strength verification is completed before demolding each batch of components.

2. Demolding Operation Essentials: Follow the principles of “loosen first, then release” and “symmetrical loading”. Large components (weighing >500kg) require vacuum suction cups to assist lifting, with lifting angle deviation controlled within ±3°. In a super high-rise project in Shanghai, Qinglong used BIM technology to simulate the demolding path, controlling the hoisting precision of 3.8m×1.2m GRC exterior wall panels within 5mm.

3. Handling Abnormal Situations: When mold adhesion occurs, forcefully striking the mold is strictly prohibited; instead, use a high-pressure water gun (pressure ≤0.3MPa) together with a plastic scraper for separation. For existing micro-cracks, Qinglong's original “micro-crack repair process” can complete repairs within 2 hours without affecting subsequent coating results.

As an enterprise that participated in drafting the Technical Standard for Building Application of Glass Fibre Reinforced Cement (GRC) (JGJ/T423-2018), Qinglong has always believed that the demolding process is the critical chokepoint of GRC component quality control. By deeply integrating materials science, structural mechanics, and intelligent monitoring technology, we have achieved an industry leap from “experience-based judgment” to “data-driven” decisions. For construction projects pursuing ultimate quality, choosing a GRC manufacturer with full-chain technical capabilities is the key to ensuring that every component is perfectly presented from production to installation.