Interaction between reinforcement corrosion and load-bearing behaviour of reinforced concrete structures

Background

Engineers are faced with the challenge of making important decisions for the design of new structures as well as for the condition assessment of ageing existing structures without having sound engineering models and concepts regarding the corrosion-related damaging mechanisms. For new structures, this challenge is generally addressed by conservative design (e.g. large reinforcement cover). For existing structures, areas at risk for reinforcement corrosion are repaired without considering whether, and when, corrosion would actually lead to a critical state if no measures were taken. These rather conservative approaches are economically and ecologically unsustainable.

Aims and objectives

The objective is to develop a novel conceptual approach combining the physical-electrochemical processes of chloride-induced corrosion with the mechanical aspects of load-deformation behavior. Based on this, we seek to devise quantitative models that allow predicting the time dependent condition development of reinforced concrete structures exposed to chlorides.

Methodology

Since this condition development results from the inherently coupled processes of corrosion initiation and propagation (cross-sectional loss of reinforcement) and load-bearing behaviour (e.g. crack opening), these two traditionally separated fields of expertise, i.e. “corrosion” and “structural load-bearing behaviour”, are here combined.

A model is developed and implemented that takes into account the mutual influence of corrosion and the load-deformation behaviour of reinforced concrete structures exposed to chlorides. Special attention is paid to the following three areas:

1. Locally corroding reinforcement is sampled from engineering structures and the corrosion pit morphology is assessed (geometry) and evaluated statistically.
2. The interaction between concrete crack opening and corrosion rate under cyclic loading and chloride exposure is studied.
3. Static models that describe the load-deformation behaviour of relevant structural systems are identified. By this, a broad applicability on structures that are exposed to chloride ingress is ensured.

A particular focus lies on the stochastic nature of localized corrosion and the relevance of the location of corrosion for the load-bearing behavior, which is considered with the Corroded Tension Chord Model (CTCM).