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51318-11166-Corrosion protection of flexible fillers coated steel strands and contaminated with fungi

Flexible fillers have been used in Europe as an alternative to cementitious grout. In this study, the corrosion resistance of PT tendons is investigated as they are coated with flexible filler materials and contaminated with fungi.

Product Number: 51318-11166-SG
Author: Francisco J. Presuel-Moreno / Carlos F. Castaneda / Fujian Tang
Publication Date: 2018
Industry: Highways & Bridges
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Over the last few decades flexible fillers such as greases or waxes have been used in Europe as an alternative to cementitious grout. The Florida Department of Transportation (FDOT) is considering flexible fillers as alternative filler materials for post-tensioned (PT) tendons. In this study, the corrosion resistance of PT tendons is investigated experimentally as they are coated with flexible filler materials and contaminated with fungi. Three types of fungi were considered including Fusarium oxysporum (FO), Penicillium chrysogenum (PC), and Aspergillus flavus (AF). The flexible fillers investigated are commercially available microcrystalline waxes, and five different filler types were investigated. Both exposure and electrochemical corrosion tests were designed and performed. As for the exposure tests, two exposure conditions were considered including direct outdoor exposure test and indoor exposure test as the greases were contaminated with fungi. Electrochemical corrosion test showed that most of the PT tendons had impedances higher than 1 Gohm and galvanic corrosion currents lower than 1 nA.

However, for PT tendons coated with filler type 3, an increase in the galvanic corrosion current and a decrease in the impedance were observed after two weeks of tests, indicating corrosion initiation. Direct outdoor exposure tests showed that rust was present on PT single wires coated with type 1, type 2, type 3, type 4, type 5 filler after 20 days, 43 days, 49 days, 114 days and 126 days of exposure, respectively. Indoor exposure tests showed that severe corrosion was present on PT single wires as their surrounding greases were contaminated by a fungi mixture. Different from the general corrosion observed on wires subjected to direct outdoor exposure tests, localized corrosion was present on indoor wires which were coated with flexible filler and contaminated with fungi.

 

Key words: Post-Tensioned Tendon, Fungi, Flexible Filler, Corrosion, EIS

Over the last few decades flexible fillers such as greases or waxes have been used in Europe as an alternative to cementitious grout. The Florida Department of Transportation (FDOT) is considering flexible fillers as alternative filler materials for post-tensioned (PT) tendons. In this study, the corrosion resistance of PT tendons is investigated experimentally as they are coated with flexible filler materials and contaminated with fungi. Three types of fungi were considered including Fusarium oxysporum (FO), Penicillium chrysogenum (PC), and Aspergillus flavus (AF). The flexible fillers investigated are commercially available microcrystalline waxes, and five different filler types were investigated. Both exposure and electrochemical corrosion tests were designed and performed. As for the exposure tests, two exposure conditions were considered including direct outdoor exposure test and indoor exposure test as the greases were contaminated with fungi. Electrochemical corrosion test showed that most of the PT tendons had impedances higher than 1 Gohm and galvanic corrosion currents lower than 1 nA.

However, for PT tendons coated with filler type 3, an increase in the galvanic corrosion current and a decrease in the impedance were observed after two weeks of tests, indicating corrosion initiation. Direct outdoor exposure tests showed that rust was present on PT single wires coated with type 1, type 2, type 3, type 4, type 5 filler after 20 days, 43 days, 49 days, 114 days and 126 days of exposure, respectively. Indoor exposure tests showed that severe corrosion was present on PT single wires as their surrounding greases were contaminated by a fungi mixture. Different from the general corrosion observed on wires subjected to direct outdoor exposure tests, localized corrosion was present on indoor wires which were coated with flexible filler and contaminated with fungi.

 

Key words: Post-Tensioned Tendon, Fungi, Flexible Filler, Corrosion, EIS

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