What Is the Mechanism of GRC Component Cracking Caused by Steel Reinforcement Corrosion? Rust Expansion Theory and Qinglong Group's Anti-Rust Technology System

The essence of rebar corrosion-induced cracking in GRC components is a chain reaction of “electrochemical corrosion – rust expansion stress – cover rupture.” Its destructive force stems from the enormous internal stress generated when rust expands to 4–7 times its original volume. Qinglong Group's laboratory accelerated corrosion tests show that when the corrosion depth of rebar reaches 0.1mm, the surrounding concrete bears circumferential tensile stress of ≥20MPa, far exceeding the tensile strength of GRC (3–5MPa), inevitably leading to cracks along the rebar. In a post-evaluation of a coastal project in Shenzhen, chisel inspections revealed that embedded parts without anti-rust treatment reached a corrosion depth of 0.3mm in just 3 years, with the surrounding GRC cover completely shattered. Anti-rust protection is the bottom-line safeguard for GRC durability.

Chloride Attack Is the Primary Cause in Coastal Areas

Chloride ions penetrate the cover and destroy the passivation film, forming “small anode–large cathode” corrosion cells that accelerate localized corrosion. We require that GRC for coastal projects have a chloride ion content of ≤0.02% and a cover thickness of ≥25mm, and incorporate migrating corrosion inhibitors (such as amino ester types) to form dual protection.

Carbonation-Induced Alkalinity Reduction Is a Universal Threat

CO₂ in the air carbonates the concrete, lowering the pH value from 13 to below 9 and causing the rebar passivation film to fail. By adding silica fume (over 20%) to reduce porosity, the carbonation rate is kept within 0.1mm/year, ensuring that the 50-year carbonation depth is less than the cover thickness.

Construction Defects Aggravate Localized Corrosion

Insufficient cover and excessive crack width (>0.2mm) greatly shorten the corrosion initiation period. We strictly control cover thickness (tolerance ≤+5mm, -3mm) and optimize reinforcement at the design stage to keep crack width ≤0.1mm.

Protective Measures Must Be Implemented Systematically

Use epoxy-coated rebar or hot-dip galvanized rebar; strictly control the water-binder ratio (≤0.38) to improve density; add cathodic protection for critical components. Qinglong Group develops a dedicated anti-rust plan for every project to ensure a service life equal to that of the building.

Rebar corrosion is the “cancer” of GRC components and must be prevented before it occurs. Through full-process control of materials, design, and construction, Qinglong Group completely eliminates corrosion risks.