Steel-concrete interface and its influence on concrete cracking in reinforced concrete
Creators: name: Chen, Fangjie
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400510
subject: Structural engineering

description: Corrosion of steel in reinforced concrete is a major contributor to material deterioration and structural failures. Accurate prediction and simulation of concrete cover cracking due to corrosion facilitates effective maintenance and rehabilitation of corrosion-affected reinforced concrete structures. The steel-concrete interface plays a pivotal role in the corrosion-induced degradation of reinforced concrete. It significantly affects the corrosion of steel and concrete cover cracking.<br> <br>This research aims to systematically investigate the influence of the steel-concrete interface on the corrosion of steel and corrosion-induced concrete cover cracking. A new method was used to examine the steel-concrete interface with the aid of a backscattered electron microscope. The effects of concrete mix design parameters, such as water-to-cement ratio, aggregate size and cover thickness on the porous band at the steel-concrete interface, were determined. Mathematical models for the distribution variation of the porous band around the steel-concrete interface were proposed.<br><br>Also, a corrosion test was conducted to investigate the corrosion of steel at the steel-concrete interface. The corrosion layer around the steel-concrete interface was quantified in various concrete mixes. The growth of the corrosion products at the porous band and subsequent corrosion-induced cracks were determined. A distribution model for the corrosion layer around the steel-concrete interface was propounded based on the experiment. Moreover, the penetration of corrosion products in cement paste around the steel bar was quantified.<br><br>The influence of concrete mixes and the corrosion of steel on the concrete cover cracking process were also investigated. Crack width, crack length and crack orientation in various concrete mixes were recorded. An image analysis approach was developed to measure the growth of crack width and crack length due to non-uniform corrosion. Further, a convolutional neural network was developed for concrete surface crack detection and measurement.<br>It was concluded that the steel-concrete interface could significantly affect corrosion-induced concrete cover cracking. The porous band was found to be non-uniformly distributed around the steel-concrete interface, the size of which ranges from a few micrometres to hundreds of micrometres. Water-to-cement ratio and cover thickness are two major factors that cause variation of porous band thickness. Also, the corrosion layer was found to be non-uniform around the steel bar due to the porous band. The proposed models for the porous band and corrosion layer can help improve the accuracy of predictive models for non-uniform corrosion-induced concrete cracking.<br><br>The merit of this research is that it provides adequate experimental evidence for the non-uniform porous band and corrosion layer at the steel-concrete interface. Comprehensive data about the porous band and corrosion layer are also presented as an input for predictive models for corrosion-induced concrete cracking. The influence of non-uniform corrosion on the growth of crack width and length is experimentally examined. Hence, the findings in this research contribute to the knowledge of corrosion-induced concrete cracking and its effect on the service life of corrosion-affected reinforced concrete structures.