Determination of Loss of Reinforcement Due to Corrosion through X-ray Computer Micro-Tomography

Abstract

X-ray computer scanning tomography (CT scan) is an increasingly more available technique, which has been applied to material sciences for years. Although most of its use is qualitative for gaining insights on material behavior, quantitative analysis for estimations of deterioration rates is possible. This paper describes an unbiased, straightforward method to determine the amount of reinforcement lost to corrosion through the use of X-ray tomography without the need to remove the concrete cover. Other methods of assessment such as gravimetric analysis, half-cell potential, resistivity of mortar cover, corrosion current, and scanning electron microscopy (SEM) are used in the same samples for comparison. While the electrical and electrochemical tests are valuable to describe the state of the samples, those demonstrated poor capacity of determining the stage of corrosion of the reinforcement in terms of amount of material lost. Electron microscopy could determine how much of the reinforcement corroded with high accuracy; however, these results are deficient in representativity, being based on a single plane of the steel. X-ray tomography, while suffering from sample size limitation, could provide quantitative information on the total volume of material lost for each sample with far higher accuracy than indirect techniques, which is significant for the forensic determination of remaining life service of structures.

X-ray computed tomography to observe the presence of water in macropores of cementitious materials

“…Already in the first applications of X-ray CT in reinforced concrete specimens [19][20][21], the relatively high attenuation coefficient of iron (and, generally, of heavy metals) gave the opportunity to clearly identify the reinforcement, observe the occurrence of corrosion attacks, and quantify the progressive development of the corrosion-induced damage. A significant number of studies have quantified the volume loss of steel due to corrosion [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] as well as measured the geometric characteristics of the corrosion sites (i.e., 2D cross-section loss) [17,38]. Generally, the available studies on the topic had two main objectives: (i) to monitor the development of corrosion over time in terms of cross-sectional loss and consequent concrete cracking [21, 26-27, 29-31, 34, 36-42], as well as (ii) to study the distribution and transport of corrosion products in the surrounding concrete matrix [21, 25, 28-29, 32-33, 35-42].…”

3D X-ray Micro-CT Analysis of Rebar Corrosion in Reinforced Concrete Subjected to a Chloride-Induced Environment

“…The progression of corrosion-induced cracks started from the concrete’s external surface and increased gradually with steel corrosion. Filho et al [ 11 ] determined the amount of reinforcement lost to corrosion through X-ray tomography on samples with induced cracking. The experimental work used an accelerated corrosion test with 3.5% NaCl solution, future SEM, and CT scan evaluation.…”