Name: Kedar Baral

Title of the project:

Modelling of reinforcement corrosion to evaluate capacity and as a tool for maintenance and repair on structural level

Project description

Background

Reinforcement corrosion is the main deterioration mechanism in marine-exposed reinforced concrete structures. Depending on the moisture level, corrosion might initiate when aggressive agents like chloride ions reach the surface of the reinforcement and accumulate to a threshold value (critical chloride content). Similarly, the propagation of active corrosion depends on both the moisture level and the concentration of these ions (including oxygen).

The service life of a structure depends on the time of corrosion onset, the rate of corrosion as well as the defined limit state (such as cracking or spalling), and the likelihood of reaching this state.

The presence of porosity, an inherent feature of concrete, makes it extremely challenging to prevent corrosion when concrete structures are exposed to corrosive environments. Therefore, it is crucial to include corrosion effects in the assessment of existing concrete structures to quantify the residual service life. These effects include reduction of the cross-sectional area and ductility of the reinforcement, alteration of the steel-concrete interface properties (adhesion), and the precipitation of the potentially voluminous corrosion products. These products may create tensile stresses in the concrete cover, leading to cracking and spalling.

Objectives

The candidate will conduct research within the field of numerical simulation of reinforcement corrosion in marine-exposed concrete structures with the overall aim to extend the service life of existing large-scale marine structures.

The candidate will develop a material level numerical model. The model should account for the main parameters controlling reinforcement corrosion with sufficient accuracy, ensuring the results are applicable as input for a large structural analysis.

Methodology

The PhD position involves both theoretical and numerical research.

During the doctoral research, emphasis will be placed on numerical simulation with the aim of developing a material-level model that accounts for the key parameters related to both general corrosion and pitting corrosion. The model will be calibrated and compared against laboratory and/or field data. It will then be used as input for structural analysis of existing structures to evaluate the structural capacity and as a tool for planning maintenance and repair.

Specific tasks comprise:

1. Review the distribution of corrosion attack in marine-exposed concrete
2. Review the distribution and type of corrosion products in marine-exposed concrete
3. Identification of critical types and levels of corrosion damage to assess the impact on the capacity of selected typical structural elements
4. Review current material-level models on the initiation and propagation of reinforcement corrosion
5. Establish a modelling framework for corrosion modelling at material level

Collaboration

The candidate will work with a team of experienced researchers within the fields of materials science and design of reinforced concrete.

The present project will be undertaking in cooperation with Equinor as part of the EXTEND project and linked to the large national research project EXCON - Green management of infrastructures, which is a “Grøn Platform” project financed by NRC.

Supervisors

1. Jan Arve Øverli
2. Mette Rica Geiker

Date of start of PhD: August 2023