Corrosion of Post-Tensioned Tendons with Deficient Grout, Part 2: Segregated Grout with Elevated Sulfate Content

Abstract

Corrosion failure of post-tensioning (PT) tendons with pre-packaged thixotropic grout has been documented in Florida bridges. Analysis of the deficient grout in Florida PT bridges, where severe corrosion developed, indicated elevated sulfate ion concentration, high pore water pH, low chloride ion content, and enhanced moisture content. Limited information is available on the corrosion behavior of PT strand in grout materials with elevated sulfate ion content. In this work, the corrosion performance of steel strands embedded in deficient grout was evaluated. The deficient grout was cast in large scale test assemblies that would represent geometry and material conditions found in Florida bridges, where PT strand corrosion occurred. Large scale mock up tendons (developed by the modified inclined tube [MIT] test) of about 4.57 m long were cast using expired grout materials, excess of 15% water, and sulfate ion concentrations to create deficiencies and corrosion conditions in the grout environment. Corrosion measurements such as corrosion potential (Ecorr) and corrosion current density (icorr), as well as potentiodynamic polarization tests were performed on the steel probes located along the MIT samples in contact with the deficient grout. Grout characterization parameters included the determination of the grout resistance (Rs), as well as the moisture and sulfate ion content. Also, visual inspection of the MIT samples (steel strand and steel corrosion probes) after a time was performed, as well as the corrosion products characterization. Testing confirmed that enhanced corrosion can occur in the deficient grout with high free sulfate ion accumulation.

Time-Dependent Reliability Assessment and Updating of Post-tensioned Concrete Box Girder Bridges Considering Traffic Environment and Corrosion

“…The corrosion of the strands initiated and propagated in external tendons due to voids in the grout, water penetration including chloride through an air vent, bleeding, and material segregation of grout (SMFMC 2017). It is widely known that the corrosion phenomenon in strands is a major cause of the reduction in the load carrying capacity and serviceability of PSC girder bridges (Nakamura and Suzumura 2013;Lau and Lasa 2013;Sajedi et al 2017). Similar incidents have occurred in many areas of the world, including France, the UK, the United States, and Japan (Cullington et al 2001;fib 2006;SMFMC 2017;Yoo et al 2018).…”

Risk-Based Selection of Inspection Method for External Post-Tensioning System of Bridges

“…However, the wrong grout injection method provides strand exposure [19]. Different combinations of factors in the construction category will make the grout out of specifications which are named deficient grout [30,31].…”

Development of the Large-Tonnage Pressure-Type Prestressed Anchor Cable with BFRP for Geotechnical Engineering and Its Mechanical Properties

“…Prestressed anchor cable is widely used in the slope treatment of bridges, high-speed railways, tunnels, reservoirs, underground space engineering, and so on [1][2][3][4][5]. However, the traditional anchor cable is made of steel material, which is easy to get rust in a watery environment [6][7][8][9][10]. Once the steel material gets rusts, the carried prestress by the anchor cable will significantly decrease, which can cause the failure of the anchoring engineering.…”