The Depth-Width Correlation for Shrinkage-Induced Cracks and Its Influence on Chloride Diffusion into Concrete

Area of Science:

• Civil Engineering
• Materials Science
• Concrete Technology

Background:

• Concrete durability is significantly affected by cracking, which can alter transport properties.
• Understanding the relationship between crack geometry and diffusion is crucial for predicting concrete service life.

Purpose of the Study:

• To investigate the depth-width correlation of shrinkage-induced cracks in concrete.
• To analyze the influence of these crack characteristics on concrete's diffusion properties.

Main Methods:

• Utilized restrained slab experiments to induce and quantify shrinkage cracks using image analysis.
• Measured concrete diffusion coefficients via a conductivity test method.
• Developed a series-parallel composite model incorporating depth-width scaling (λ) to evaluate diffusivity.

Main Results:

• The depth-width scaling factor (λ) of cracks increases with width, stabilizing around 0.3 mm.
• Crack tip angles were measured to be approximately 1-2 degrees.
• The equivalent diffusion coefficient is highly dependent on crack depth and shows a nonlinear relationship with crack width and λ.

Conclusions:

• Crack depth is a more critical factor than crack width in determining the diffusion coefficient of cracked concrete.
• The diffusion coefficient within the crack (D) increases with crack width, reaching a constant value 87% of the free solution diffusion coefficient for widths > 0.2 mm.