PT GROUT: BLEED WATER VOIDS

Portland cement grout has been used to fill post-tensioning (PT) ducts in North America since the 1950s. This article describes how PT grouts were used in the past and suggests research to determine if common grouting practices are based on facts or myths. The goal is to further improve grout properties, techniques and procedures. Although PT grout bleed and how to control water separation was well-known in the early 1970s, many in the PT industry did not accept that water separation caused significant voids in tendon ducts and anchorages until 2001. Better quality control can be obtained if mixing and pumping practices for prebagged, water-retentive grout are properly executed. For large projects, the use of water-retentive admixtures is more economical. Successful PT grouting requires: a water retentive grout, designed for the vertical rise of the tendon, that will bond and protect the prestressing steel and anchorage from corrosion; proper high-quality mixing and compatible pumping equipment; knowledgeable quality control oversight; and an awareness by all participants that the intent of grouting is to fill ducts, encapsulate the prestressing steel and anchorages, and to seal and waterproof all penetrations to the duct and anchorage.