How to Control the Thickness of the Steel Reinforcement Protective Layer in GRC? Anti-Corrosion Design and Structural Optimization Solutions by Qinglong Group

Controlling the thickness of the rebar protective layer in GRC is a key structural measure for preventing corrosion-induced expansion and ensuring structural durability. Based on long-term engineering experience and research into corrosion mechanisms, Qinglong Group specifies that the minimum protective layer thickness shall be no less than 15mm, and should be increased to 20mm in humid, coastal, or de-icing salt environments. This thickness must balance protective effect against component cross-sectional dimensions; our calculations show that increasing the protective layer from 15mm to 20mm can extend the time for carbonation to reach the rebar surface from 30 years to over 50 years. Precision control requirements are strict, with allowable deviations of +3mm and -0mm; on site, rebar positioning clamps are used to ensure accurate placement.

The design of protective layer thickness must comprehensively consider environmental aggressiveness, component service life, and rebar diameter. In coastal projects such as the Hainan International Convention and Exhibition Center, Qinglong Group applies a 20mm protective layer to all load-bearing rebars and adds an epoxy resin coating to stirrups. We use finite element simulation of chloride ion diffusion paths to optimize the matching relationship between protective layer thickness and concrete density, avoiding unnecessary cross-section enlargement while ensuring adequate protection.

Construction control is key to achieving the required thickness. Qinglong Group uses customized high-strength plastic spacers with a compressive strength of ≥50MPa, arranged at no fewer than 4 per square meter. In spray application, we first cover the rebar with 5mm of fiber-free mortar before spraying the GRC mix, preventing fibers from directly contacting the rebar and forming corrosion channels. We require supervisors to conduct a full inspection of protective layer thickness, verified with a rebar scanner, and the pass rate must reach 100%.

Special areas require special treatment. At vulnerable locations such as edges and openings, we add stainless steel anti-crack mesh and increase the protective layer to 25mm. Qinglong Group recommends clearly specifying the testing methods and acceptance criteria for protective layer thickness in acceptance contracts—this is the foundation for ensuring the long-term safety of GRC components.