PhD Project: Thermodynamic modelling of chloride migration into concrete

This PhD research project investigates the thermodynamic modelling of chloride migration in concrete exposed to accelerated chloride ingress conditions, with particular focus on replicating and predicting the results of the NT Build 492 Rapid Chloride Migration (RCM) test using the geochemical modelling software PHREEQC. Chloride-induced corrosion of reinforcing steel is one of the primary causes of deterioration in reinforced concrete infrastructure. Accurately predicting chloride transport and binding within concrete is therefore essential for improving service-life assessment and durability design. The research aims to develop a robust thermodynamic framework capable of simulating chloride penetration, interaction with cement hydration products, and changes in pore solution chemistry over time. Experimental chloride concentration profiles obtained from NT Build 492 tests will be compared against model predictions to evaluate and refine the accuracy of the proposed modelling approach.

The long-term performance of reinforced concrete structures is strongly influenced by the ingress of chloride ions, particularly in marine environments and regions where de-icing salts are used. As chlorides penetrate concrete and accumulate at the depth of embedded reinforcement, the passive oxide layer protecting steel can be disrupted, initiating corrosion and leading to significant structural and economic consequences. Traditional service-life models often represent chloride transport using simplified diffusion-based approaches that neglect important chemical interactions occurring within the cementitious matrix.

This research seeks to address these limitations through the application of thermodynamic modelling using PHREEQC, a widely used geochemical simulation platform capable of representing complex chemical equilibria in porous materials. The project will develop a reactive transport framework that incorporates chloride binding mechanisms, pore solution chemistry, cement hydrate phases and mineral transformations occurring during chloride exposure. Particular attention will be given to the interaction of chlorides with hydration products which significantly influence the distribution and mobility of chlorides within concrete.

Experimental data will be obtained from NT Build 492 Rapid Chloride Migration tests conducted on concrete specimens with varying material compositions and exposure durations. Chloride concentration profiles will be measured at different depths from the exposed surface and at multiple stages of testing. These experimental profiles will provide the basis for calibrating input parameters and validating the PHREEQC models.

The predicted chloride concentration distributions generated by the thermodynamic simulations will be directly compared with the measured profiles to assess model performance. The research aims to improve current understanding of chloride transport mechanisms and establish the suitability of thermodynamic modelling as a tool for durability assessment. Ultimately, the study will contribute to the development of more mechanistic and reliable service-life prediction models for concrete infrastructure, supporting improved durability design, maintenance planning and resilience of reinforced concrete structures exposed to chloride-rich environments.

Student Requirements for this Project 2.1 in and Honours Civil or Structural Engineering degree

Self Funded (Scholarship not available. Fees & Materials to be paid by the student. Materials costs not significant)

www.tudublin.ie/explore/faculties-and-schools/engineering-built-environment/transport-and-civil-engineering/

If you are interested in submitting an application for this project, please complete an Expression of Interest. forms.office.com/e/0hCcrv2Gkp