The effects of climate change on the rates of chloride ingress into reinforced concrete in seaport infrastructure
Creators: name: hunting, andrew
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400505
subject: Construction materials
classificationCode: 400508
subject: Infrastructure engineering and asset management
classificationCode: 400510
subject: Structural engineering

description: The process of chloride ingress into concrete is the most destructive method of concrete deterioration and is currently costing developed countries approximately 2.5% of national annual GDP. As the effects of climatic change become more evident and extreme, there is growing pressure on seaport infrastructure stakeholders to ensure that their assets are resilient to the effects of a more aggressive and corrosive climate. In almost all previous literature on condition modelling of concrete structures, a static or at least annually cyclic environment is assumed. However, given the anticipated changes in climatic parameters, this research is aimed to address the need for understanding the impact of a changing climate on chloride ingress into concrete.<br><br>A comprehensive review of literature identified the current models of chloride ingress in concrete, as well as experimental procedures adopted in measuring chloride ingress in the laboratory. Also, a review of literature on climate models predicting future climate are examined. The major gap in knowledge is identified as the inability of the current models of chloride ingress into concrete to account for the changes in sea salinity as a consequence of climate change. The Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) was selected as the document to guide the research.<br><br>A comprehensive experimental program was planned and conducted to understand the effect of environmental parameters on chloride ingress in concrete. Parameters investigated include salinity, humidity, temperature, and concrete mix design. Quantification of chloride ingress was achieved through permeability testing, chloride content testing at various depths and x-ray tomographic studies. Results of the experimental study clearly indicated that environmental changes had a significant impact on the chloride ingress rates within concrete.<br><br>Using a statistical analysis, an empirical relationship was developed referencing environmental parameters and chloride ingress in concrete. Microtomographic studies provided a 3D quantification of voids within the concrete samples. A numerical model was developed to forecast corrosion initiation time using the newly developed equation for forecasting chloride ingress as an influence of sea salinity. The model was used to predict the corrosion initiation time in a port structure. Results indicated a good agreement with the chloride measurements in the port structure which was proven with a further numerical analysis on the statistical significance. A remedial treatment was examined in the laboratory using a well-planned experimental study. Effectiveness of the treatment was measured in the laboratory using Scanning Electron Microscopy, permeability, flexural and compressive strength testing, as well as carbonation and chloride ponding tests. Whilst the treatment examined did not demonstrate a convincing benefit, the study conducted led to development of a comprehensive methodology for evaluation of treatment options.<br><br>Another major finding of the research is the observation that the environmental conditions and subsequent chloride ingress influence changes in the microstructure of surface concrete demonstrating an increase in degradation of the concrete leading to an increased porosity. The research in this area need to be continued to further examine this effect.