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Civil MDC

Test Method for Bleed Stability of Cementitious Post-Tensioning Tendon Grout 2

Test Method for Bleed Stability of Cementitious Post-Tensioning Tendon Grout

Description

he majority of durability problems found in grouted post-tensioned structures are related to voids in the grout due to incomplete filling of ducts or bleeding of the grout. Voids in the grout within the duct result in a loss of the protective environment and may end up as a collection point for moisture or outside contaminants such as saltwater. Voids can be formed from water separation from the grout before setting. Bleed water may remain trapped in the tendons or may be reabsorbed into the hardened grout, leaving voids. Bleeding increases with vertical pressure head.

This test method is designed to evaluate the bleed stability of a freshly-mixed grout under static pressure. It can be used in both the laboratory to qualify grout materials and in the field as a quality-control test. When used to qualify grout materials, replicate tests may be specified. It is intended thatthe test pressure, acceptance criteria, and number of replicate tests be set forth in the Contract Documents. These values will generally vary depending on the vertical rise of the post-tensioning tendon. Appendix A is an example set of test pressures and acceptance criteria.


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