Title: Flexible filler mock-up injections of bridge post-tensioning tendons
Date Published: May - June 2018
Volume: 63
Issue: 3
Page Numbers: 65 - 76
Authors: Natassia R. Brenkus, Rahul Bhatia, Will A. Potter, and H. R. Hamilton III
https://doi.org/10.15554/pcij63.3-02

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Abstract

This paper presents the results of five mock-up injections of post-tensioning tendons with flexible filler material. The objective of the mock-up injections was to assess standard grout injection procedures for use of flexible filler materials instead of cementitious products. The focus was on developing an understanding of the procedural aspects and injection equipment of the injection. Each 200 ft (61 m) long tendon had a deviated profile to simulate strand and duct placements and inclination angles found in typical segmental box girders and internal tendons of drop-in spans (parabolic). Each tendon was composed of 19 prestressing strands with 0.6 in. (15 mm) diameters (with nominal pretensioning of approximately 1 kip/strand [4 kN/strand] to achieve the desired profile), a smooth high-density polyethylene duct, a commercially available flexible filler material, and a post-tensioning anchorage system. Variables included the injection procedures (pumping equipment, flow rate, injection pressure, inlet/outlet location, and venting), the post-tensioning anchorage system, and the filler material. Internal duct pressure and surface temperature, as well as filler material temperature, were measured during and shortly after injection. Despite procedural variations and the use of various filler materials, all prestressing strands in every mock-up injection were well coated with filler material, as observed in next-day dissection of the tendons. This work influenced the subsequent development of specifications for flexible filler injection procedures.

References

Parsons Brinckerhoff. 2012. “Un-bonded Tendon System Practices for Bridges in Europe.” Report prepared for FDOT (Florida Department of Transportation) Design Office.

Brenkus, N. R., A. B. M. Abdullah, R. Bhatia, D. Skelton, J. A. Rice, and H. R. Hamilton. 2017. “Replaceable Unbonded Tendons for Post-tensioned Bridges: Final Report.” Final report prepared for FDOT, contract BDV31- 977-15. University of Florida, Department of Civil and Coastal Engineering.

FDOT. 2018. Section 462. In Standard Specifications for Road and Bridge Construction. Tallahassee, FL: FDOT.

Abdullah, A. B. M., J. A. Rice, R. Bhatia, N. R. Brenkus, and H. R. Hamilton. 2016. “A Thermal Analysis of Flexible Filler Injection for Unbonded Post-tensioning Tendons.” Construction and Building Materials 126: 599–608.