Recent durability studies on concrete structure

Freeze-thaw durability of recycled concrete containing ceramic aggregate

Corrosion of the reinforcement and its influence on the residual structural performance of a 26-year-old corroded RC beam

Bond behaviour with reinforcement corrosion

Effects of confinements on the bond strength between concrete and corroded steel bars

Experimental study of the material and bond properties of frost-damaged concrete

It is not uncommon that cover cracking, spalling, and delamination occur in many corroding RC structures. Previous research has mainly been concerned with corrosion levels leading to cover cracking along the main reinforcement, whereas corrosion of stirrups is often overlooked. Corrosion phenomena, including stirrup corrosion, were studied in an experimental investigation presented in this paper. High levels of corrosion were reached, up to 20% of the main bars and 34% of the stirrups legs. The occurrence of crack initiation, propagation, and cover delamination were examined. The specimens had the shape of a beam end and were corroded with an accelerated method; an imposed current was used, taking care to keep the current density as low as practically possible for the duration of the laboratory testing. The effects of this process were compared with those of natural corrosion using models from the literature. The location of the bar, middle and corner placement, the amount of transverse reinforcement, and the corrosion level of longitudinal reinforcement and of transverse reinforcement were studied. The results concerning the concrete cracking in the experimental campaign are presented. The crack patterns and widths were analyzed, showing differences between specimens with or without stirrups and whether stirrups were corroding. Finally, the effect of corrosion was simulated as the expansion of corrosion products in a finite-element (FE) model, and the results, mainly the crack pattern and width, were compared with the test results. The conclusions addressed the importance of taking into consideration both high corrosion levels and corrosion of stirrups for the assessment of deteriorated structures.

https://publications.lib.chalmers.se/records/fulltext/175310/local_175310.pdf

Severely Corroded RC with Cover Cracking

This paper presents a methodology to analyze the mechanical behavior and remaining load-carrying capacity of corroded reinforced concrete (RC) structures. The methodology is used to predict the mechanical behavior for a structure with an observed amount of uniform and pitting corrosion at a given time. The effect of corrosion is modeled as a change in geometry and properties of corroded reinforcement and surrounding concrete—that is, a reduction of steel area and ductility, removal of spalled concrete, modification of concrete response due to corrosion cracks, and modification of bond-slip properties. The methodology is applied to concrete beams affected by reinforcement corrosion, using both finite element analyses and analytical methods. A comparison of the results with available experiments from the literature indicated that the changes in failure mode and failure load caused by uniform and pitting corrosion of reinforcement can be predicted reasonably well by using the proposed methodology.

https://publications.lib.chalmers.se/records/fulltext/145262/local_145262.pdf

Analysis of Mechanical Behavior of Corroded Reinforced Concrete Structures

Eccentric pull-out tests were carried out to study the influence of severe corrosion leading to extensive cover cracking, and the effect of corroded and non-corroded stirrups on the anchorage of deformed bars. The specimens were subjected to a low-rate electrochemical corrosion process for three time spans that caused a rebar weight loss up to approximately 20% in the main bars and 35% in the stirrups. Pull-out tests were then carried out in each specimen, on either the two corner bars or the middle bar, to measure the bond capacity. The effects of corrosion and the mechanical testing were simulated with non-linear finite-element analysis. The combination of tests and analyses gives a better understanding of the effect of high corrosion penetrations and the presence of corroded Stirrups on failure modes. The presence of stirrups, corroded and non-corroded, was found to significantly change the behavior of an anchorage region, namely the corrosion-induced crack pattern, the failure mode and the bond capacity.

http://publications.lib.chalmers.se/records/fulltext/147244/local_147244.pdf

Bond capacity of severely corroded bars with corroded stirrups

A methodology is introduced to predict the mechanical behavior of reinforced concrete ‎structures with an observed amount of frost damage at a given time. It is proposed that the ‎effects of internal frost damage and surface scaling can be modeled as changes of material ‎and bond properties, and geometry, respectively. These effects ‎were studied and suggestions were made to relate the compressive strength and dynamic modulus of elasticity, as the indicators of damage, to the response of the damaged concrete in compression and tension, and to the bond behavior. The ‎methodology was applied to concrete beams affected by internal frost damage, using ‎non-linear finite element analyses. A comparison of the results ‎with available experimental data indicated that the changes in failure mode and, to a rather large extent, the effect on failure load ‎caused by internal frost damage can be predicted. However, an uncertainty was the extension and distribution of the damaged region which affected the prediction of the load capacity.‎

Kamyab Zandi Hanjari

Papers

Experimental study of the material and bond properties of frost-damaged concrete

Severely Corroded RC with Cover Cracking

Analysis of Mechanical Behavior of Corroded Reinforced Concrete Structures

Bond capacity of severely corroded bars with corroded stirrups

Modelling the structural behaviour of frost-damaged reinforced concrete structures