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Accelerated Corrosion Testing of Grouts for PT Steel Strand
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2021-04-01
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Edition:March 2018 – July 30, 2021
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Abstract:Protection afforded by the post-tension system components often are effective to prevent corrosion of the steel strand; however, there have been cases of corrosion related to grout voids and bleed water. There were cases where the non-bleed thixotropic grouts, used to prevent bleed, had corrosion associated with grout segregation. Prescribed testing generally focused on preventing bleed water formation and chloride contamination but did not address the effects of developed grout deficiencies such as segregation. Other test methods, such as the rapid macrocell, test has also been used in research for steel strand in grouts. It was of interest to assess corrosion testing methods to identify grout robustness and corrosion mitigation to adverse construction. Testing here included methods that promote the development of grout deficiencies, including overwatering, grout prehydration, and flow restrictions for the grouts in vertically deviated setups such as the incline tube test and the inverted-tee test (INT). The work explored modifications to the Post-Tensioning Institute (PTI) accelerated corrosion test and the rapid macrocell test, implementing components of the inverted-tee test. Corrosion testing using the modified incline tube test and electrochemical noise technique were considered as well. Different levels of physical grout deficiencies were visually evident for the thixotropic grout when mixed with excess 10% water. The results showed that the INT setup with the vertical deviation can produce enhanced transport of moisture and sulfate ions towards the top of the tee header and that application of these test specimens can be implemented in existing test guidelines to assess grout robustness and corrosion propensity in deficient grout. Electrochemical noise was shown to be an effective measurement technique to assess the development of localized corrosion of steel in alkaline sulfate solution.
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[PDF-7.66 MB]
