Title:
Development of Test Method to Detect Soft Grout Formation in Prepackaged Post-Tensioning Grouts
Author(s):
Alex Piper, Alexander J. Randell, Brett Brunner, and H. R. (Trey) Hamilton
Publication:
Materials Journal
Volume:
122
Issue:
5
Appears on pages(s):
3-12
Keywords:
bleed; duct; grout; post-tensioning; segregation; soft grout; tendon
DOI:
10.14359/51747868
Date:
9/1/2025
Abstract:
This paper presents research focused on the development of a test method that can be used to gauge the susceptibility of a post-
tensioning (PT) grout to form soft grout. Depending on the grout formulation, soft grout may have a lower pH, retain excessive moisture, and be corrosive to the tendon. While relatively rare, it has been documented in bridge construction in the United States and abroad, and in some cases has prompted the replacement of PT tendons.
One of the causes of soft grout is thought to be the use of low-
reactivity fillers such as ground limestone. When tendons deviate significantly, these fillers can segregate and then accumulate into a mass of material that does not harden. The modified inclined tube test (MITT) was developed based on the Euronorm inclined tube test. None of the commercially available PT grouts produced soft grout when they were mixed and injected in accordance with manufacturer’s recommendations and tested well before their expiration date. Additional mixture water or residual water in the tube, however, produced soft grout consistently in one of the PT grouts.
Related References:
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