What Is the Mechanism by Which Steel Corrosion Causes GRC Component Cracking? — An In-Depth Analysis of Rust Expansion Effects and Prevention Technologies

Cracking of GRC components caused by steel reinforcement corrosion is a typical durability problem, with its mechanism rooted in the internal stress generated by the volume expansion of corrosion products. Based on accelerated testing and verification in actual projects, Qinglong Group has determined that the volume of corrosion products is 2-4 times that of the original steel, and the resulting expansion stress can reach more than 30MPa—far exceeding the tensile strength of GRC (3-5MPa)—causing the protective cover to crack. Through strict anti-rust measures, this risk can be reduced to a minimum.

The corrosion process is divided into three stages: in the early stage, corrosion products fill the pores of the protective cover with no noticeable stress; in the middle stage, corrosion products accumulate and generate radial tensile stress; in the later stage, the protective cover cracks and corrosion accelerates. Tracking data from Qinglong Group's coastal projects show that corrosion begins when chloride ions penetrate to the steel surface and their concentration reaches a critical value (0.05%-0.1%). Insufficient cover thickness (＜15mm) significantly shortens the time to cracking. In Hainan's high-temperature, high-humidity environment, components with a 20mm cover have a predicted time to cracking of up to 30 years, while 15mm components may develop cracks within 15 years.

Prevention and control measures are systematic. Increasing the density of the protective cover achieves a chloride diffusion coefficient ≤2.0×10⁻¹²m²/s. Qinglong Group significantly improves impermeability by incorporating active admixtures such as silica fume. Epoxy-coated or galvanized steel reinforcement is adopted to extend the corrosion induction period. Regular inspections are carried out, and rust stains are treated promptly when found. These measures effectively safeguard the long-term safety of components.