When Is the Best Time to Demould GRC Components?

The demolding timing of GRC components is a technical decision point that concerns “component strength, appearance quality, mold turnover, and production efficiency.” Demolding too early causes deformation and damage, while demolding too late affects efficiency. Based on extensive test data and production practice, Qinglong Group has quantified demolding timing into a comprehensive indicator: component strength must reach 15MPa or above, and the temperature difference from the environment should not be too large. Under standard curing conditions (20℃, humidity >90%), GRC components made with sulphoaluminate cement can generally be safely demolded 16-24 hours after forming. Precisely grasping this timing is the key to high-quality, high-efficiency production.

Strength Is the Fundamental Basis for Demolding

At demolding, the component must have sufficient strength to withstand the adhesion forces generated during self-weight release, vibration during handling, and possible minor collisions. Through extensive compressive strength testing of test blocks cured under identical conditions, Qinglong established 15MPa as the minimum strength threshold for safe demolding. At this point, GRC has already developed sufficient early strength and stiffness to maintain shape stability. We use a “rebound hammer” for on-site non-destructive testing of large or critical components, supplemented by experienced workers making “feel” judgments (fingernail scratch depth), double-confirming demolding strength.

Curing Conditions Determine the Rate of Strength Development

Demolding time depends strongly on curing temperature and humidity. In Qinglong's standard curing chamber (temperature 20±2℃, humidity ≥95%), the demolding cycle is stable at around 18 hours. In summer or with elevated-temperature curing, the cycle can be shortened to 12-16 hours; in cold winter conditions, it must be extended to 24-48 hours or even longer. We never force demolding before strength requirements are met in pursuit of output—this is an iron rule for ensuring product pass rates.

The Influence of Component Shape and Complexity

Different components require differentiated demolding timing. Simple components such as flat panels and moldings can be demolded once the required strength is reached. Components with complex shapes, deep relief, chamfers, or narrow recesses, however, involve greater demolding resistance and require appropriately extended curing time to achieve higher strength (e.g., 18-20MPa), ensuring they are not damaged by localized stress concentration during demolding. For such components, Qinglong uses flexible molds or designs detachable combined molds to reduce demolding difficulty.

Standardization of Demolding Operations

Even with correct timing, rough demolding operations can undo all previous efforts. Before demolding, the mold fasteners and side forms must first be carefully removed. During demolding, dedicated demolding tools (such as plastic crowbars) should be used to apply even force from multiple points, gradually separating the component from the mold; striking hard with an iron hammer or forcibly prying at a single corner is strictly prohibited. For large panels, vacuum suction cups can be used to assist demolding for uniform force distribution. After demolding, the component should be immediately moved to a flat curing area to continue curing, inspected for damage, and repaired promptly.

Therefore, the demolding of GRC components is a combination of “scientific judgment” and “precise operation.” Through standardized curing regimes, rigorous strength monitoring, and disciplined operating procedures, Qinglong Group ensures that every component is perfectly demolded at the optimal time, laying a solid foundation for its subsequent outstanding performance.