Author : Chantal Chalhoub
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (129 download)
Book Synopsis Study of the Initiation and Propagation Phases of Chloride Induced Corrosion in Reinforced Concrete Structures by : Chantal Chalhoub
Download or read book Study of the Initiation and Propagation Phases of Chloride Induced Corrosion in Reinforced Concrete Structures written by Chantal Chalhoub and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: It is commonly accepted that chloride-induced corrosion of steel is one of the most documented causes leading to the deterioration of reinforced concrete structures. The Ph.D. study aimed at the improvement of the understanding of chloride-induced corrosion in concrete during the transition phase between initiation and propagation and during the corrosion propagation phase. Traditionally, chloride-induced corrosion is initiated when the chloride content reaches a threshold value called critical chloride content or Ccrit. In spite of much research invested in this domain, there is still no agreement on an accurate method for the determination of the chloride threshold value initiating corrosion. The first objective of this work was to develop a new test set-up that considers the localized character of corrosion initiated by chlorides. This approach was based on a physical separation between the anode, contaminated with chlorides, and the cathode, which is chloride free. The experimental protocol will allow quantifying the galvanic corrosion current, making it possible to determine, in a second step, the chloride threshold values for corrosion initiation. The criterion for corrosion initiation was a threshold corrosion current defined as a current that is independent of the cathode/anode surface ratio and subsequently independent of the area of passive steel. This criterion was considered as an anodic control of corrosion during the transition stage from the initiation phase to the propagation phase. This test protocol was applied to mortar and concrete formulations with several types of binders (CEM I cement, CEM III cement and CEM I with silica fume) with different water/binder ratios embedding ribbed steel bars with different steel surface conditions (as received, chemically cleaned, chemically cleaned than oxidized with humidity or high temperature). It was found that the test protocol is rapid and applicable to all formulations. The experimental results provide an understanding of the influence of binder type, w/b ratio and porosity on the susceptibility of steel to chloride-induced corrosion initiation. The steel surface condition was found to have an important overall effect on corrosion initiation but this effect is dependent on the type of binder used. Several literature studies considered that chloride-induced corrosion initiation is under anodic control which could mean that corrosion is controlled by the electrochemical parameters of steel. The parameters of passive steel can be directly derived from experimental measurements owing to the uniform passive state of rebars. However, because of the non-uniform nature of chloride-induced corrosion in concrete, it is not possible to experimentally obtain uniformly active steel. In this thesis, the determination of the electrochemical properties of active steel was achieved based on inverse numerical modeling focusing on the dependence of these properties on chloride contamination. All the experimental observations coupled with the numerical modeling approach highlighted the dependency of the electrochemical properties of active steel on chloride content. When dealing with macrocell corrosion, it is crucial to consider the geometry and size of the structure, including the mobilizable cathode-anode distance and the cathode to anode surface ratio.