Probing the steel-concrete interface microstructure using FIB-SEM nanotomography

Area of Science:

• Materials Science
• Civil Engineering
• Corrosion Science

Background:

• The steel-concrete interface (SCI) is critical for reinforced concrete durability, but its features influencing corrosion are poorly understood.
• Complex SCI heterogeneity and lack of suitable experimental techniques hinder research.

Purpose of the Study:

• To apply focused ion beam-scanning electron microscopy (FIB-SEM) nanotomography for high-resolution 3D imaging of the SCI.
• To characterize the SCI's pore structure and its relevance to transport phenomena.

Main Methods:

• Utilized FIB-SEM nanotomography to acquire 3D tomograms of non-corroded and corroded SCIs.
• Developed an image processing pipeline for artifact reduction and segmentation into solid and pore phases.
• Analyzed pore structure using diffusion tortuosity and porosity profiles.

Main Results:

• Achieved voxel sizes of 30-50 nm, capturing relevant capillary pores for moisture and ion transport.
• Identified pronounced anisotropy in the SCI pore structure.
• Highlighted potential pitfalls and detector considerations for FIB-SEM application on SCI.

Conclusions:

• FIB-SEM is a viable technique for high-resolution tomographic analysis of SCI pore structure.
• Digital analysis of FIB-SEM data can inform transport models for improved concrete durability predictions.