Control Methods for Reinforcement Cover Thickness in GRC: Standard Requirements, Process Measures and Engineering Practice

Proper control of rebar protective cover thickness in GRC is key to preventing rebar corrosion and ensuring component durability and structural safety. Different application scenarios and environments impose explicit requirements on cover thickness, which must be achieved through scientific design and precise production processes. As a leading enterprise in the GRC industry, Qinglong has established a mature cover thickness control system across hundreds of GRC projects with steel frameworks, ensuring long-term stable service of its products.

Standard requirements for rebar protective cover thickness must be determined in light of the environment and component type. According to the Technical Standard for Application of Glass Fiber Reinforced Cement (GRC) in Buildings (JGJ/T423-2018), for GRC components in indoor dry environments, the rebar protective cover thickness should be no less than 15mm; in outdoor or humid environments, it should be increased to more than 20mm; under harsh conditions such as coastal salt spray or cold freeze-thaw environments, the cover thickness should be no less than 25mm. In the GRC faux-stone component project for the Dongting Lake Museum, due to the humid environment, Qinglong set the cover thickness at 22mm, combined with anti-corrosion coatings to effectively block moisture and chloride ion attack, ensuring the rebar remains rust-free over the long term. For large load-bearing GRC components, the cover thickness must be determined through structural verification calculations to avoid stress concentration caused by insufficient thickness.

Mold design and rebar positioning are the core of cover thickness control during production. Qinglong uses 3D modeling technology for detailed mold development, setting positioning bosses or spacer block slots on the mold inner wall to ensure the distance between the rebar framework and the mold inner wall precisely matches the design thickness; when fabricating the rebar framework, dedicated plastic spacer blocks (with strength no lower than that of the GRC matrix) are used, with spacing controlled at 500-800mm and evenly distributed around the rebar framework to avoid locally insufficient cover thickness. In the GRC special-shaped double-curved panel project for Hainan Poly Peninsula No. 1, because of the complex component shapes, Qinglong simulated rebar positions using BIM technology and customized special-shaped spacer blocks, ensuring the cover thickness deviation at all parts of the double-curved components was ≤±2mm, meeting design requirements.

Construction techniques and quality inspection are key links in ensuring control effectiveness. During casting or spray-up forming, avoid direct impact on the rebar framework to prevent displacement that would cause cover thickness deviation; when using vibration and pressurization processes, control vibration intensity and duration to ensure the GRC slurry fully fills the gaps between rebar and mold while avoiding slurry segregation. Qinglong has established a strict in-process inspection regime, using ultrasonic thickness gauges to randomly sample formed components at a sampling rate of no less than 3%, and reworking components whose thickness deviation exceeds the allowable range (±3mm). In the GRC cladding panel project for Guangzhou Dongzhu Shangdu Commercial City, full-process inspection ensured a 100% pass rate for the cover thickness of all components, providing a guarantee for the project's long-term safety.

Qinglong's rebar protective cover thickness control technology has been successfully applied in numerous landmark projects such as the Shenzhen Pingshan High-tech Zone Comprehensive Service Center and the Guangxi New Media Center. For designers and owners, thicker cover is not necessarily better; the thickness must be determined comprehensively based on component shape and mechanical performance while meeting durability requirements, making it essential to choose a supplier with precise control capabilities. With 28 years of process accumulation and testing experience, Qinglong integrates cover thickness control into the entire process of design, production, and inspection, ensuring that every GRC component delivers reliable structural safety and durability.