51316-7810-Feasibility of Cathodic Protection in Grouted Post Tensioning Tendons

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Product Number: 51316-7810-SG

ISBN: 7810 2016 CP

Author: Alberto Sagues

Publication Date: 2016

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[Note Author order: Jacob Bumgardner and Alberto Sagues].Post-tensioning strands are made with highly cold worked eutectoid steel and protected from corrosion by the presence of high pH cementitious grout injected in the ducts that contain the tendon strands. Some combination of grouting deficiencies chloride contamination bleeding water cracks or carbonation may result in localized strand corrosion and subsequent failure by cross section loss or stress corrosion cracking. Corrosion control is challenging due to difficulty in accessing the inside of the tendon and uncertainty as to the location of the corroding section. The high risk associated with tendon failure has led to the evaluation of increasingly imaginative means of corrosion control including the use of pre-placed internal anodes for cathodic protection of the strand bundle. Such application is a significant engineering challenge as even if the anode is properly separated from direct strand contact the protective current distribution may not be sufficiently uniform and because the conditions of operation must avoid reaching adverse steel polarization regimes where hydrogen embrittlement may occur. In this work Finite Element Modeling on a multiphysics platform is used to examine the current distribution and operating regimes that may be feasible to achieve a uniform and safe cathodic protection application envelope. The simulations include the use of single or multiple anodes and address a set of plausible steel polarization parameters duct geometries and grout characteristics. Suitability of the concept is assessed for a selection of expected possible application scenarios toward developing a conceptual design and working parameters for later development.