Penetration Of Corrosion Products Research Articles

Distribution of corrosion products at the steel-concrete interface: Influence of mill scale properties, reinforcing steel type and corrosion inducing method

In this study, corrosion products of a Cr-bearing low-alloy (LA) steel and the conventional low-carbon (LC) steel with intact mill scale at the steel-concrete interface were investigated by means of backscattered electron (BSE) images. Furthermore, the effect of mill scale properties and corrosion inducing methods (long-term natural exposure to chloride solution and accelerated corrosion by chloride electromigration) on the distribution and penetration of corrosion products was compared. Complex interactions were highlighted between the corrosion products and the mill scale of LC and LA steels at the steel-concrete interface. In addition, different corrosion patterns of both steels were evident when subjected to different corrosion inducing methods.

Non-Destructive Testing of Archaeological Findings by Grating-Based X-Ray Phase-Contrast and Dark-Field Imaging

The analysis of archaeological findings reveals the remaining secrets of human history. However, it is a challenging task to investigate and simultaneously preserve the unique remains. Available non-destructive examination methods are limited and often insufficient. Thus, we considered X-ray grating interferometry as a non-destructive and advanced X-ray imaging method to retrieve more information about archaeological findings. In addition to the conventional attenuation image, the differential phase and the dark-field image are obtained. We studied the potential of the scattering-sensitive dark-field and the phase-shift sensitive differential phase image to analyse archaeological findings. Hereby, the focus lies on organic remnants. Usually, the organic materials have vanished due to decomposition processes, but the structures are often preserved by mineralisation and penetration of corrosion products. We proved that the combination of the attenuation and the dark-field image in particular, enables a separation of structural properties for fabric remnants. Furthermore, we achieved promising results for the reconstruction of sub-pixel sized fibre orientations of woven fabric remnants by employing the directional dark-field imaging method. We conclude from our results that a further application of X-ray dark-field imaging on wet organic findings and on the distinction of different types of organic remnants at archaeological findings is promising.

Penetration of corrosion products and corrosion-induced cracking in reinforced cementitious materials: Experimental investigations and numerical simulations

This paper describes experimental investigations on corrosion-induced deterioration in reinforced cementitious materials and the subsequent development and implementation of a novel conceptual model. Reinforced mortar specimens of varying water-to-cement ratios were subjected to current-induced corrosion (10, 50, and 100μA/cm2). X-ray attenuation measurements and visual investigations provided both qualitative and quantitative information on the penetration of solid corrosion products into the surrounding cementitious matrix. X-ray attenuation measurements provided time- and location-dependent concentrations of corrosion products averaged through the specimen thickness. Digital image correlation (DIC) was used to measure corrosion-induced deformations including deformations between steel and cementitious matrix as well as formation and propagation of corrosion-induced cracks. Based on experimental observations, a conceptual model was developed to describe the penetration of solid corrosion products into capillary pores of the cementitious matrix. Only capillary pores within a corrosion accommodating region (CAR), i.e. in close proximity of the steel reinforcement, were considered accessible for corrosion products. The conceptual model was implemented into a FEM based cracking model and compared to experimental results provided in the literature and obtained from DIC measurements.

Distribution of millscale on corroded steel bars and penetration of steel corrosion products in concrete

This study investigated a reinforced concrete specimen that had deteriorated in an artificial environment for 2years. The steel/concrete interface and corrosion-induced cracks were observed by SEM to investigate the millscale on the rebar surface and the distribution of rust. The millscale was not further oxidised before the surface cracking of the concrete cover. The penetration of corrosion products into concrete and the formation of a corrosion layer proceeded simultaneously. The rust did not fill the corrosion-induced cracks in concrete. Instead of the three-stage model, a two-stage model is proposed to describe the concrete cracking process induced by steel corrosion.

Analysis of crack propagation due to rebar corrosion using RBSM

Cracking behavior due to rebar corrosion in concrete specimens having a single rebar is evaluated experimentally and analytically. In the experiments, in which corrosion was induced electronically, the propagation of cracks (including internal crack patterns and surface crack widths) was monitored. In addition, deformation of the specimen surface was measured using a laser displacement meter. In the analysis, a three-dimensional Rigid-Body-Spring Method (RBSM), combined with a three-phase material corrosion–expansion model, is proposed to simulate crack propagation due to rebar corrosion. The effects of the properties of corrosion products such as elastic modulus, penetration of corrosion products into cracks, and local corrosion after cracking of the concrete are investigated. Cracking behavior due to rebar corrosion is simulated reasonably well. The simulations using RBSM provide insight into the mechanisms of crack initiation and propagation due to rebar corrosion.

Experimental Investigation of Corrosion-Induced Cover Cracking in Reinforced Concrete Structures

Concrete cover cracking induced by reinforcement corrosion is an important problem in reinforced concrete structures. Several existing analytical models for cracking time are discussed, and it is found that the penetration of corrosion products into corrosion cracks is neglected in these models. Based on our study, a theoretical model that takes the ingress of rust into cracks into account is proposed to predict the cracking time. In order to analyze the amount of corrosion products deposited in cracks, an accelerated corrosion test was performed. Based on the experimental results, the parameter k, which deal with the ingress of corrosion products into cracks, is calibrated to be 0.1~0.3 for accelerated corrosion test. By comparing the predictions with the test results, it is found that the proposed model has high accuracy in analyzing the cracking time and that the mean absolute error between predictions and observations is about 9.4%.

On the penetration of corrosion products from reinforcing steel into concrete due to chloride-induced corrosion

Abstract Reinforced concretes were corroded to varying degrees by exposing to cyclic NaCl spray and 40 °C drying. The amount of corrosion products and induced damage were measured using image analysis. We found that corrosion products can accumulate at steel–concrete interface as well as penetrate cement paste and deposit within hydration products, relicts of reacted slag, and air voids. As corrosion increases, the products tend to accumulate at the steel–concrete interface, while the amount penetrating cement paste remains relatively constant. Only a small amount of corrosion is needed to induce visible cover cracking. Implications on modelling time to cover cracking are discussed.

Penetration of metallic ions from restorations into teeth

The efflux of metal ions from metal restorations and their penetration into dental tissues have been studied with the use of sophisticated techniques. The results show significant concentrations of metal ions in both enamel and dentin from amalgam, chromium-cobalt, and cast-gold restorations after short periods in or on the teeth. The highest concentrations occurred in the regions closest to the restorations, especially within the dental tubules cut during cavity preparation. It was also shown that use of pure cohesive-gold or nearly pure cast-gold restorations or heat-treatment (homogenization) of gold castings for sufficiently long periods reduced the corrosion of gold restorations and the penetration of corrosion products into dental tissues. Use of a cavity liner was found to prevent migration of corrosion products from metal restorations into teeth.