What Is the Mechanism by Which Steel Corrosion Causes GRC Component Cracking? Qinglong GRC Rust Expansion Cracking Mechanism and Prevention Techniques

Cracking of GRC components caused by steel reinforcement corrosion is a complex electrochemical process. Its essence is that the volume expansion of rust generates tensile stress on the surrounding matrix, and when the stress exceeds the tensile strength of the matrix, cracking occurs. Through microstructural testing and long-term observation, Qinglong GRC has systematically revealed the full-process mechanism of corrosion-induced expansion cracking.

In the failure analysis of a coastal project, core drilling and electron microscopy scanning of cracked components revealed: the volume of corrosion products (Fe(OH)₃, Fe₃O₄) is 2-6 times that of the original steel, generating expansion pressure as high as 30-50MPa, far exceeding the tensile strength of GRC (3-5MPa). Energy spectrum analysis showed that chloride content had accumulated to 0.8% on the steel surface, which is the main cause of pitting corrosion. By establishing a prediction model for corrosion-induced expansion cracking, the full process from the onset of corrosion to the appearance of surface cracks was accurately back-calculated to have taken 28 months.

Analysis of the Electrochemical Corrosion Mechanism

Chloride ions destroy the passive film and form corrosion cells; carbonation by carbon dioxide reduces alkalinity (pH dropping below 9); oxygen and moisture constitute the necessary conditions for corrosion. This electrochemical process causes the corrosion rate to grow exponentially.

Development Patterns of Corrosion Expansion Stress

Initial stress appears when the corrosion rate reaches 0.5%; microcracks emerge at 1%; when it exceeds 2%, cracks propagate through. Expansion stress has a quadratic relationship with corrosion depth, and crack width is proportional to the amount of corrosion.

Identification of Crack Morphological Characteristics

Longitudinal cracks along the reinforcement are a typical feature, with widths of 0.1-0.3mm; in severe cases, mesh-like cracks appear with spacings of 50-100mm; when the cover layer spalls, crack widths can exceed 1mm. These features help assess the degree of corrosion.

Sensitivity Analysis of Influencing Factors

Cover thickness has the greatest influence: an increase of 10mm in thickness delays the onset of corrosion by 5 years; reducing the water-cement ratio by 0.05 lowers the chloride diffusion coefficient by 50%. These parameters are key to anti-corrosion design.

Corrosion-induced expansion cracking requires systematic prevention and control. The anti-corrosion technology system of Qinglong GRC extends the service life of components to more than 50 years in harsh environments.