When is the Best Time to Demold GRC Components?

The selection of GRC component demolding timing directly affects product quality and production efficiency, requiring comprehensive consideration of strength development, environmental conditions, and component characteristics. Through 28 years of process optimization, Qinglong Group believes that demolding timing should be scientifically determined based on component strength, size, and shape, typically controlled to occur when compressive strength reaches 5-10MPa, ensuring both product integrity and efficiency.

Strength development is the primary basis for determining demolding timing. Qinglong Group uses a penetration resistance meter for on-site testing; when strength reaches 5MPa, initial demolding (side form removal) can be performed, and when it reaches 10MPa, final demolding (bottom form removal) is carried out. Under standard curing conditions (20±2℃, humidity ≥95%), ordinary GRC components reach initial demolding strength 12-16 hours after casting and final demolding strength in 24-36 hours. In the Yangshengtang Pharmaceutical Hangzhou Industrial Park project, demolding time was shortened to 8-12 hours by incorporating early-strength agents (lithium carbonate dosage 0.5%-1%), improving mold turnover rates.

Environmental conditions have a significant impact on demolding timing. For every 5℃ increase in temperature, the strength development rate increases by approximately 30%. During summer construction, Qinglong Group controls ambient temperature below 35℃ through mist cooling to avoid premature demolding. In winter, heated curing is adopted to ensure the core temperature does not fall below 10℃. In the Algeria hotel project, facing high-temperature conditions, we used retarding water reducers to extend setting time, ensuring thorough hydration before demolding. When relative humidity is below 60%, curing time should be extended by 2-4 hours to prevent surface moisture loss and cracking.

Component characteristics determine the demolding method. Thin-walled components (thickness <20mm) develop strength quickly but are prone to deformation, requiring appropriately extended demolding time. In the Shanghai Century Plaza translucent UHPC project, Qinglong Group adopted stepped demolding for 15mm thick panels: side forms were loosened first, and bottom forms removed after 24 hours. Special-shaped components can only be demolded after the strength at edges and corners reaches 15MPa to avoid damage. Mass components require controlled cooling rates, with immediate covering for curing after demolding to prevent thermal stress cracking.

Demolding operations must be performed in a standardized manner. Non-load-bearing formwork is removed first, followed by load-bearing formwork, with the removal sequence being the reverse of the installation sequence. Qinglong Group uses specialized demolding equipment to avoid excessive force. After demolding, component quality is inspected and any issues are promptly addressed. Scientific control of demolding timing keeps the product qualification rate stable above 99%.