How to Control the Thickness of the Steel Reinforcement Cover in GRC?

The thickness of the protective cover for rebar (or embedded parts) in GRC is a lifeline for preventing corrosion and ensuring durability. It must be determined comprehensively based on “environmental class, component function, and rebar diameter,” typically 15-25mm. Based on 28 years of engineering practice, Qinglong Group has clearly specified in its “GRC Component Construction Atlas”: ≥ 15mm in dry indoor environments, ≥ 20mm in humid outdoor environments, and ≥ 25mm in coastal areas or chemical plant zones. In the Shenzhen Yirui Biotechnology Building project, we used custom high-precision plastic spacers (tolerance ±0.5mm) and rebar positioning fixtures to achieve a 100% pass rate for the 20mm cover thickness, safeguarding a 50-year service life for the components. Cover control is the detail critical to the long-term safety of GRC.

Thickness Design Must Match the Environment

According to the “Standard for Durability Design of Concrete Structures”, environmental classes range from Class I to Class V, with the cover thickness increasing accordingly. Qinglong Group uniformly adopts a 25mm cover in coastal projects (Class IV), with added rust inhibitor for dual protection.

Construction Control Is Key to Achieving the Thickness

Use dedicated spacers (strength ≥ that of the component), no fewer than 4 per square meter; re-check rebar positions with a rebar detector before pouring; stepping on rebar is strictly prohibited. We require workers to be certified for their roles, with a construction tolerance ≤ ±3mm.

Remedies and Prevention for Insufficient Thickness

When insufficient cover is found, it must be chiseled off and re-cast, or treated with a penetrating rust inhibitor. Through BIM pre-assembly, Qinglong Group identifies conflicts between rebar and embedded parts in advance, avoiding thickness loss caused by on-site adjustments.

Though small, the protective cover bears on overall safety. Qinglong Group has incorporated cover control into its work instructions and conducts third-party testing to ensure foolproof results.