United States Department of Transportation
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Guidelines for Sampling, Assessing, and Restoring Defective Grout in Prestressed Concrete Bridge Post-Tensioning Ducts [Tech Brief]
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2013-05-01
[PDF-144.76 KB]
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Abstract:This document is a technical summary of the Federal Highway Administration report, "Guidelines for Sampling, Assessing, and Restoring Defective Grout in Prestressed Concrete Bridge Post-Tensioning Ducts" (FHWA-HRT-13-028). The objectives of this study were to provide recommended guidance for grout sampling, testing, data analysis, and interpretation of results and to propose courses of action by State transportation departments where grout deficiencies are identified. Grout is a cementitious material typically used to provide corrosion protection to the prestressing strands used in post-tensioned (PT) concrete bridges. Based on collected information and data analysis, State transportation departments can evaluate if grout deficiencies are present in the tendons of their PT bridges and determine the significance of those deficiencies. Durability concerns associated with PT tendons were raised as early as 1999. Tendon failures were seen in some PT bridges as a result of strand corrosion due to the collection of bleed water in grout voids at tendon profile locations like anchorages and crest areas. While the development of prepackaged thixotropic grout was thought to provide a solution to the bleed water problem, corrosion-caused tendon failures on relatively new PT bridges have occurred, and the forensic studies performed to-date have revealed separation and segregation of grout materials as well as the presence of soft material, free water, and high chloride, and sulfate content in some instances. Consequently, it is important to examine the overall quality of materials and construction for some in-place grouts in existing PT bridges. The product of this study is a guide for State transportation departments to employ in sampling in-place grouts from tendons in PT bridges.
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