How to Prevent Cracking of GRC Components During Setting: Key Techniques and Practical Measures

In the field of architectural decoration, GRC components have become the "aesthetic centerpiece" of numerous landmark buildings thanks to their lightweight, high-strength properties and rich variety of shapes. However, cracking during setting is like a hidden "chronic ailment of buildings" — it not only affects appearance and structural safety, but may also increase later maintenance costs. As an industry player with 28 years of deep experience in UHPC/GRC/GRG/GRP materials, Qinglong Group, drawing on full-chain practical experience covering material proportioning, process control, and environmental management, has developed a systematic anti-cracking solution that provides actionable technical reference for the industry.

The "Invisible Killer" of GRC Component Cracking: The Dual Test of Materials and Processes

The causes of cracking during the setting of GRC components are complex and varied, with the core conflict lying in the imbalance between material shrinkage and structural stress. In ordinary GRC materials, the hydration reaction of the cement matrix is accompanied by volume shrinkage. If the bonding at the glass fiber–cement matrix interface is poor, or the fiber distribution is uneven, stress concentration occurs and micro-cracks form. In a commercial complex project, cornice line components developed surface cracking within 24 hours after setting; testing revealed that the glass fiber content was below 1.5% and fiber agglomeration had occurred during mixing, ultimately resulting in insufficient crack resistance. At the detailed design stage, Qinglong uses BIM technology to simulate the stress distribution of components. Combined with 28 years of engineering data, fiber content is strictly controlled at 2.5%–3%, and planetary mixers are used to ensure uniform fiber dispersion, reducing cracking risk at the source.

A Full-Process Anti-Cracking System: A Technical Closed Loop from Formula Optimization to Intelligent Curing

Preventing cracking of GRC components requires a full-process control system spanning "design–production–curing." At the material formula level, Qinglong's R&D team, through orthogonal experiments, combines silica fume, mineral powder and other admixtures in a 3:1 ratio to replace 20% of the cement content, reducing hydration heat while improving matrix density. At the same time, nano calcium carbonate modification technology is introduced, increasing early strength by 30% and reducing plastic shrinkage cracks. In production, a "layered pouring + vibration compaction" process is adopted, with built-in vent holes for components thicker than 80mm to prevent residual air bubbles from creating stress weak points. In the curing stage, an intelligent temperature control system is activated: components are cured for 7 days at 20℃±2℃ with humidity ≥90%, followed by gradient cooling that keeps the day-night temperature difference within 5℃, effectively suppressing thermal stress cracking.

Field Experience: Detail Control in Anti-Cracking for Large-Scale Projects

In a cultural landmark project in Nanjing, the double-curved GRC curtain wall panels undertaken by Qinglong measured up to 3.6m×1.8m with a curvature radius of only 250mm, posing extreme construction difficulty. The technical team innovatively adopted a "pre-crack control joint" design, reserving V-shaped grooves 2mm wide and 5mm deep at component corners, filled with elastic sealant, successfully releasing stress. Meanwhile, 3D laser scanning positioning was used during on-site installation, keeping errors within ±2mm and avoiding additional stress caused by installation misalignment. Three years after delivery, the project has shown no cracking whatsoever, confirming the effectiveness of the systematic anti-cracking solution. In addition, the Technical Standard for Building Application of Glass Fiber Reinforced Cement (GRC) (JGJ/T423-2018), whose development Qinglong participated in, clearly specifies the curing parameters for GRC components in different environments, providing standardized guidance for the industry.

Preventing the setting-related cracking of GRC components is essentially a systematic engineering effort to balance material performance, process precision, and environmental factors. Built on 28 years of full-chain experience, Qinglong Group has kept its cracking rate below 0.3% through material innovation, intelligent production, and refined management — far below the industry average. Looking ahead, as UHPC/GRC composite technology develops, we will continue to explore lighter and stronger anti-cracking solutions, providing technical support for the mission of "creating beautiful architecture" and helping designers turn more creative ideas into safe and durable works of architectural art.