Surface Strain Evolution and Cracking Behavior of Concrete Under Non-Uniform Corrosion-Induced Expansion Monitored by...

Area of Science:

• Civil and Structural Engineering
• Materials Science
• Corrosion Engineering

Background:

• Steel corrosion-induced cover cracking is a major threat to reinforced concrete durability in marine environments.
• Non-uniform rust expansion stresses necessitate high-resolution monitoring for crack initiation and propagation.
• Existing monitoring techniques lack the continuous, in situ resolution required for these complex processes.

Purpose of the Study:

• To investigate the effectiveness of distributed optical fibers for in situ monitoring of concrete surface strain.
• To systematically analyze the influence of specimen length, biochar content, cover thickness, and rebar diameter on corrosion-induced cracking.
• To provide a quantitative basis for durability assessment and continuous monitoring of reinforced concrete structures in marine environments.

Main Methods:

• Distributed optical fibers utilizing Rayleigh backscattering were embedded to monitor surface strain in concrete specimens.
• In situ monitoring was conducted to capture strain evolution under simulated marine environmental conditions.
• Systematic variation of specimen length, biochar content (0.5%), cover thickness (25-40 mm), and rebar diameter (12-20 mm) was employed.

Main Results:

• Surface strain evolution exhibited a two-stage pattern: slow growth (pore filling, stress accumulation) followed by rapid rise (crack propagation).
• Increased specimen length amplified strain non-uniformity; 0.5% biochar reduced average strain by 17% and delayed cracking; increased cover thickness (to 40 mm) reduced strain by 39% and delayed cracking significantly.
• Reduced rebar diameter decreased peak strain; macro-cell effects driven by chloride gradients were key to crack initiation locations.

Conclusions:

• Distributed optical fiber sensing provides a reliable method for in situ monitoring of corrosion-induced strain and crack initiation.
• Biochar incorporation, increased cover thickness, and reduced rebar diameter effectively mitigate cracking, with cover thickness showing the most pronounced effect.
• The study offers quantitative data for enhancing the durability assessment and monitoring strategies for concrete structures exposed to marine environments.