Estimating Post-Tensioning Grout Bleed Resistance Using a Pressure-Filter Test

Abstract

Grouted tendons are found in the precast, prestressed concrete industry in a number of applications, including post-tensioned tendons added for live load and continuity requirements in pretensioned bridge girders. A key property for a high quality grout is proper bleed resistance. Bleed water trapped in the grouted duct collects at high points and forms voids, leaving steel more vulnerable to attack by aggressive agents. This paper summarizes available pressure-filter test data of grouts along with actual pumping tests over the last 34 years. The data are combined with a calculated pressure approach for determining the required bleed resistance suitable for a particular elevation change. A procedure for carrying out a pressure filter test is given and three numerical design examples for various post-tensioning applications are included. Recommendations are provided for structural elements with high, medium, and low elevation changes. The use of these recommendations should result in grouts that produce a reasonably small amount of bleed water.