How to Control Reinforcement Cover Thickness in GRC: Key Technologies and Quality Assurance Measures

In the field of construction engineering, the thickness of the rebar protective cover is like an "invisible shield," directly affecting the durability and safety of structures. Especially in new composite material components such as GRC (Glass Fiber Reinforced Concrete), scientifically controlling the cover thickness is both a technical challenge and a quality bottom line. As an industry leader with 28 years of deep expertise in UHPC/GRC/GRG/GRP materials, Qinglong Group will systematically explain how to control rebar cover thickness in GRC components, from material properties and process innovation to full-process quality control.

Special Requirements of GRC Material Properties on Cover Thickness

GRC components are composed of glass fiber and cement-based materials, combining the advantages of lightweight high strength and flexible shaping, and are widely used for exterior wall cladding panels and decorative lines of high-end buildings such as grand theaters and commercial complexes. Compared with traditional concrete, the thin-wall characteristic of GRC (usually only 50-80mm thick) imposes more stringent requirements on the rebar cover: too thin easily leads to rebar corrosion, while too thick may cause component cracking. In the detailed design stage, based on the project environment (e.g., coastal high-humidity areas require an additional 2-3mm of cover) and in accordance with the Technical Standard for Building Application of Glass Fiber Reinforced Cement (GRC) (JGJ/T423-2018), Qinglong Group accurately calculates rebar spacing and cover thickness parameters through BIM models.

Mold and Rebar Positioning Technology: Process Assurance with Millimeter-Level Precision

Control of cover thickness begins with mold design. Qinglong adopts high-precision steel molds and modular design, with PE plastic spacer slots preset on the inner walls of molds to ensure spacer position deviation ≤2mm. In production, the innovative "3D laser scanning + robotic arm rebar placement" technology is applied, controlling rebar cage positioning error within ±1mm through real-time coordinate calibration. For complex double-curved GRC components (such as the special-shaped ribbons in the Dongguan Women and Children's Activity Center project), Qinglong developed dedicated adjustable rebar fixing brackets, combined with an RFID chip traceability system, achieving full life-cycle records of cover thickness for each component.

Collaborative Optimization of Material Mix and Forming Process

The stability of cover thickness depends on the compatibility of materials and processes. Qinglong adjusts the fluidity of GRC slurry (flow spread controlled at 220±10mm) and fiber content (3-5% by volume) to ensure the slurry fully wraps the rebar during casting without segregation. In the spray-up forming process, the "layered spraying + vacuum degassing" technology is adopted, increasing the cover density by more than 15%. For the light-transmitting GRC components in the Century Plaza renovation project on Nanjing East Road, a composite cover system of glass fiber mesh and rebar was innovatively introduced, meeting the light transmittance requirements while controlling cover thickness deviation within ±5% of the design value.

Industry Practice of a Full-Chain Quality Control System

As a national "specialized, refined, distinctive, and innovative" enterprise, Qinglong has established "five lines of defense" from raw material inspection to finished product delivery: strict selection of low-alkali cement and alkali-resistant glass fiber at the raw material stage; sampling inspection of cover thickness every 2 hours during production (using non-destructive radar detection instruments); three-point bending tests before delivery to verify the bond strength between the cover and rebar; use of 3D positioning brackets during on-site installation; and a 5-year cover thickness tracking inspection service after project completion. This full-process control model has kept the first-pass acceptance rate of cover thickness for Qinglong's overseas projects (such as a landmark building in Malaysia) at 100%.

Control of rebar cover thickness is the core guarantee of GRC component quality, and a direct reflection of a material supplier's technical strength. Backed by 28 years of full-chain experience, Qinglong Group transforms this seemingly simple parameter into a competitive advantage for engineering quality through technological innovation and rigorous quality control. In the future, with the wide application of UHPC/GRC composite components, Qinglong will continue to drive the iterative upgrading of cover control technology, laying a solid quality foundation for the mission of "creating aesthetically beautiful buildings."