What Are the Characteristics of the Material Mix Ratio for Lightweight GRC Molding?

Lightweight GRC shapes aim to minimize the self-weight of components while ensuring the necessary mechanical performance. The core of its material mix design lies in "optimizing the aggregate system, improving fiber efficiency, and introducing micro-porous structures," thereby achieving a unity of high strength and light weight. To meet the needs of projects with large panel sizes, high openwork ratios, or strict weight restrictions, Qinglong Group has developed a variety of dedicated lightweight GRC mix designs, with a density controllable within 1.6–1.8 g/cm³, over 20% lighter than standard GRC (approximately 2.0–2.1 g/cm³), while its mechanical performance still meets application requirements.

The key technical route to achieving lightweighting is to replace part or all of ordinary sand with lightweight aggregates. Commonly used lightweight aggregates include expanded shale, expanded ceramsite, cenospheres, and closed-cell glass microspheres. These aggregates are filled with micro-pores internally and have very low inherent density. Through extensive testing, Qinglong selected high-quality closed-cell glass microspheres or modified expanded ceramsite with high strength and low water absorption as the main lightweight aggregates. Their particle sizes have been optimized through grading, forming a dense particle packing system with cementitious materials such as cement and silica fume, ensuring the strength of the matrix while reducing weight.

Effective fiber distribution is the key to ensuring toughness. The matrix strength of lightweight GRC is usually lower than that of standard GRC, so the reinforcing and toughening effect of glass fiber is even more important. It is essential to ensure that fibers are uniformly dispersed during mixing and to avoid clumping. Qinglong adopts a process of dry mixing first followed by wet mixing with batch feeding, and uses high-efficiency polycarboxylate superplasticizers to improve slurry workability, so that fibers are fully coated by the cement slurry and form a three-dimensional, randomly oriented reinforcement network, thereby giving the material excellent crack resistance and toughness.

Introducing controllable micro air bubbles can also reduce density to a certain extent. By adding a small amount of air-entraining agent, a large number of uniform, closed tiny bubbles are introduced into the slurry. However, these bubbles reduce strength, so the dosage must be strictly controlled to find the optimal balance between density and strength. Qinglong's lightweight GRC mix designs have undergone rigorous mechanical performance and durability testing, ensuring that while reducing self-weight, they still possess good impact resistance, freeze-thaw resistance, and impermeability, providing a material foundation for architects to achieve lighter and more dynamic architectural forms.