What Are the Material Mix Characteristics of Lightweight GRC Shapes? Lightweight High Strength and Qinglong Group's Mix Proportion Optimization Technology

The core of the material mix design for lightweight GRC modeling lies in achieving a balance of "high strength, light weight, good toughness, and durability," with the key technical path being the synergy of four elements: "low water-binder ratio, optimized aggregates, high-efficiency fibers, and reactive mineral admixtures." The mix proportion developed by Qinglong Group specifically for lightweight components controls the water-binder ratio at 0.32-0.36 by incorporating ultra-light aggregates (such as glazed hollow beads), a large proportion of mineral admixtures (fly ash + silica fume ≥40%), and high-range water reducers, reducing the dry density to 1.6-1.8 g/cm³ (15-20% lighter than standard GRC) while maintaining flexural strength above 12-15MPa. In the large openwork suspended ceiling project of the Shenzhen Yirui Biotechnology Building, this lightweight formula kept the weight of components with individual areas of up to 8㎡ within 120kg, successfully achieving the artistic effect of large spans and high openwork, while improving installation efficiency by 40%. Lightweighting is an important development direction for GRC technology.

Low Water-Binder Ratio and High-Range Water Reducers Are the Cornerstone of Strength

Lowering the water-binder ratio is key to improving strength and reducing porosity. However, a low water-binder ratio results in poor workability, so high-range polycarboxylate water reducers (water reduction rate ≥30%) must be relied upon to ensure the fluidity and sprayability of the mix. In our mix proportions, the water-binder ratio is typically controlled at around 0.33, and the water reducer brings the flow spread to 600-700mm, meeting the requirements of spray forming.

Lightweight Aggregates and Gradation Optimization Are Key to Achieving Light Weight

Partially replacing traditional quartz sand with lightweight aggregates is the most direct and effective method of weight reduction. We use closed-cell glazed hollow beads or expanded ceramsite with a bulk density ≤800kg/m³, whose particle sizes form a continuous gradation with quartz sand, ensuring that weight is reduced without compromising the density and strength of the system. The dosage of lightweight aggregates needs to be optimized through testing, typically 20-40% of the total aggregate.

Fiber Selection and Distribution Ensure Toughness

Lightweight GRC places higher demands on toughness. We use alkali-resistant glass fibers (ZrO₂ content ≥16%), 12-20mm in length, at a volume dosage of 2.5-3.5%. Through the robotic spraying process, the fibers are ensured to be uniformly distributed in three-dimensional random orientations within the matrix, forming an efficient spatial network that inhibits crack propagation, exhibiting excellent pseudo-ductility even under thin-wall conditions.

Reactive Mineral Admixtures Enhance Durability and Workability

High volumes of fly ash and silica fume (totaling ≥40%) not only replace part of the cement to reduce costs; their micro-filling effect and pozzolanic activity significantly optimize the pore structure, improving impermeability and corrosion resistance. At the same time, the admixtures improve the cohesion and water retention of the mix and reduce bleeding, which benefits fiber dispersion and surface quality.

Designing lightweight GRC mix proportions is a complex optimization process. Through extensive orthogonal tests and microscopic testing, the Qinglong Group laboratory customizes optimal material solutions for customers' various application scenarios, helping buildings develop toward lighter, stronger, and more beautiful forms.