Three-dimensional characterization of the steel-concrete interface by FIB-SEM nanotomography

TL;DR

This study employs high-resolution FIB-SEM nanotomography to 3D characterize the steel-concrete interface at the microstructural level, providing insights into corrosion mechanisms affecting reinforced concrete durability.

Contribution

It introduces the use of FIB-SEM nanotomography for detailed 3D analysis of the steel-concrete interface, surpassing previous imaging techniques in resolution and scale.

Findings

Achieved voxel resolution of 30-50 nm for detailed microstructural imaging.

Captured 3D tomograms of both non-corroded and corroded interfaces.

Provided datasets for creating digital twins to study durability and corrosion.

Abstract

While it is widely accepted that the steel-concrete interface (SCI) plays an important role in governing the long-term durability of reinforced concrete structures, understanding about the primary features of the SCI that influence corrosion degradation mechanisms has remained elusive. This lack of knowledge can be attributed, on the one hand, to the complex heterogeneous nature of the SCI, and, on the other hand, the absence of experimental techniques suitable for studying the relevant features of the SCI. Here, we use focused ion beam - scanning electron microscopy (FIB-SEM) nanotomography to obtain high resolution 3D tomograms of the steel-concrete interfacial zone. Five tomograms, spanning volumes ranging from 8,000 to 200,000 cubic micrometer, were acquired for situations representative of both non-corroded and corroded SCIs. The achieved voxel size falls within the range of 30-50 nm, thus providing a resolution clearly surpassing the capabilities of computed X-ray tomography. This resolution enables the 3D characterization of the microstructure at the capillary scale, which is the scale at which relevant corrosion and related mass transport processes occur. Thus, FIB-SEM nanotomography is capable of yielding datasets of the SCI that serve as basis for the generation of digital twins of the interfacial microstructure, thereby enabling future studies about durability and corrosion of reinforced concrete at the pore scale.