How to Prevent Cracking of GRC Components During Setting?

To prevent cracking of GRC components during setting, efforts must begin from four dimensions: material optimization, production processes, curing control, and installation design, with the core focus on controlling shrinkage stress and thermal stress. Through refined whole-process management, Qinglong has reduced the component setting-cracking rate to below 0.3%; projects such as Panzhihua in Sichuan and Fengjingwan in Nanning have had no setting-cracking issues.

1. Material Optimization: Enhancing Basic Crack-Resistance Performance

The material mix is the core guarantee against cracking. Fiber optimization: alkali-resistant glass fibers (length 12-15mm) are selected with a dosage controlled at 2.2-2.5% to form a three-dimensional reinforcement network; Qinglong fibers use an end-hooked type, improving bond strength with the matrix by 20% and crack-resistance strength by 30%. Admixture addition: a polycarboxylate high-range water reducer (dosage 0.8-1.2%) is added to lower the water-cement ratio to 0.38-0.42 and reduce drying-shrinkage cracking, and an expansion agent (dosage 3-5%) is added to compensate for shrinkage stress; all Qinglong admixtures pass compatibility tests with no adverse reactions. Aggregate optimization: low-water-absorption aggregates (mud content ≤0.3%) are selected to avoid drying shrinkage after the aggregates absorb water; Qinglong aggregates are washed and oven-dried, with water absorption ≤1%.

2. Production Process Control: Reducing Stress Generation

The production process controls stress concentration. Mold design: components with complex shapes use segmented molds with reserved shrinkage joints to avoid stress concentration during integral forming; the molds for Qinglong's double-curved components for the Guangxi New Media Center are segmentally designed, releasing 50% of shrinkage stress. Vibration control: high-frequency vibration (≥2500 times/min) ensures compactness (≥2.2g/cm³), while avoiding over-vibration that causes aggregate segregation; Qinglong controls vibration time at 30-60 seconds per layer. Pouring sequence: following the principle of "bottom-to-top, symmetrical pouring" to avoid shear stress caused by uneven slurry flow; Qinglong uses robotic pouring for large components, with a uniform and controllable pouring speed.

3. Curing and Installation Design: Releasing Residual Stress

Later stages resolve potential cracking risks. Gradient curing: after demolding, components first undergo 3 days of high-temperature, high-humidity curing (temperature 20-25°C, humidity ≥95%), followed by 4 days of natural curing to slowly release thermal stress; Qinglong curing rooms maintain temperature and humidity precision of ±1°C, reducing cracking risk by 60%. Avoiding early loading: during the setting period (within 7 days), moving, stacking, or applying external force is prohibited; Qinglong components may only be transferred after 7 days of curing, when strength reaches 70% of the design value. Flexible installation design: installation joints use elastic gaskets with 5-8mm expansion joints reserved to absorb shrinkage deformation; the installation joints in Qinglong's Shenzhen Pingshan High-tech Zone project received flexible treatment, with no installation-induced setting cracking.