Electrochemical behavior of galvanized reinforcing steel in chloride-contaminated concrete

Name: Dewi, Melati Sari

keyword: Electrochemical properties

; Corrosion

; Galvanized steel

; Chloride

; COMSOL simulation

; Service life

Abstract: Corrosion due to chloride attack is a problem that is often encountered in the field, especially in areas close to the sea and can occur in structures that have been contaminated with chlorides. Chloride damages the reinforcing steel directly, thereby reducing the life of the reinforced concrete structures when attacked. In this study, modifying the mixed proportion as well as the reinforcing steel used in construction is an alternative to increasing the service life. Galvanized steel has zinc on its outermost layer and zinc has a more negative electrode potential than bare steel. Zinc can be sacrificed when corrosion occurs. The objective of this study is to observe the corrosion behavior of three types of reinforcing steel, i.e. bare steel (BS), galvanized steel (GS), and corroded galvanized steel (CGS). Three types of binders used in this study include PCC, FA and OPC with variations of 0.4 and 0.6 water-to-binder ratio, and chloride content of 0, 0.75, and 1.5% by weight of binder. Experiments in the laboratory were carried out by measuring electrochemical properties. The experimental methods were non-destructive tests including the Wenner four probe, PPR, LPR, and HCP. Also, titration test to measure the chloride content and MIP to measure the porosity were conducted. The electrochemical properties results were used to calculate the corrosion rate and predict the service life at the corrosion initiation until corrosion cracking (propagation). Simulation using COMSOL software was carried out to see the illustration of the corrosion that occurs in the concrete structure using the electrochemical properties as the parameters. Based on the experimental results, The variation of mix proportion affects the electrochemical properties of the corrosion of the reinforcing steel. The water-to-binder ratio of 0.4 had better resistance against corrosion than those with 0.6 w/b and the resistance of steel became lower with higher chloride content. Fly ash concrete had a denser pore structure causing high concrete resistivity at a longer age. Cement with Portland composite cement (PCC) had a high strength at an early age and had a denser pore structure when incorporating chloride. This caused the concrete resistivity to increase and the current density to decrease, so that corrosion of the steel was low. The simulation of corrosion using COMSOL showed the electrode potential and current density of the steel in the concrete. Finally, service life prediction showed that galvanized steel (GS) had a longer service life than that of corroded galvanized steel (CGS) and bare steel (BS) according to the corrosion rate and the service life prediction

Thammasat University. Thammasat University Library

Address: BANGKOK

Email: preserv@tu.ac.th

Name: Pakawat Sancharoen

Role: advisor

Name: Iyoda, Takeshi

Role: co-advisor

Created: 2022

Modified: 2023-12-25

Issued: 2023-12-25

วิทยานิพนธ์/Thesis

application/pdf

DOI: 10.14457/TU.the.2022.762

eng

DegreeName: Master of Science

Level: Master's Degree

Descipline: Engineering and Technology

Grantor: Thammasat University

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