How to Prevent Cracking of GRC Components During Setting? An In-Depth Analysis of Qinglong's GRC Anti-Cracking Technology System

The cracking of GRC components during the setting and hardening stage is a core challenge affecting their durability and safety. Through 28 years of technical accumulation, Qinglong GRC has developed a full-process anti-cracking technology system based on material modification, with process control as the key and curing regimes as the safeguard.

In a double-curved roof project for a cultural center in Wuhan, to meet the crack-prevention requirements of large-span thin-walled components (15mm thickness), Qinglong's technical team adopted triple anti-cracking technology: at the material level, polypropylene fiber (0.9kg/m³) and expansive agent (6%) were added; in the process, layered spraying was adopted with single-layer thickness controlled at ≤8mm; during the curing stage, an automatic mist-spraying system kept the component surface humidity continuously ≥95%. None of the 3,200㎡ curved roof panels installed in the project showed any structural cracks.

Material System Anti-Cracking Technology

Sulphoaluminate cement is used to reduce chemical shrinkage; well-graded microsilica (5%-8%) is added to optimize the pore structure; polypropylene fiber (0.6-1.0kg/m³) is incorporated to enhance early tensile strength. Through material modification, early tensile strength is increased by 40% and the shrinkage rate is reduced by 35%.

Mix Proportion Optimization Design

The water-cement ratio is strictly controlled within 0.32-0.35; the sand-binder ratio is optimized to 1:1.2-1.5; shrinkage-reducing admixture (1.5-2%) is added to effectively suppress plastic shrinkage. Tests show that the 24-hour drying shrinkage value of the optimized mix proportion is ≤0.15%.

Precision Control of the Production Process

Vacuum dewatering is used to reduce the moisture content below 18%; spraying thickness is controlled in stages, with each single layer ≤10mm; the curing kiln adopts gradient heating (≤15℃/h). Through process optimization, thermal stress is reduced by 50%.

Scientifically Formulated Curing Regime

A three-stage regime of "curing in mold + moisture-retention curing + drying curing" has been established: 24 hours of curing in the mold with humidity ≥95%; 7 days of mist-spraying curing with the water loss rate controlled at ≤0.2kg/m²·h; 21 days of natural drying curing. Temperature fluctuation throughout the whole process is controlled within ±3℃.

Crack control is a systematic project. Qinglong GRC's anti-cracking system has been successfully applied to multiple large-scale projects, with the cracking complaint rate reduced to below 0.3%.