Single strand tendons offer an efficient, economical, and practical way of post-tensioning many types of building structures. The use of single strand tendons seems to increase every year. Unfortunately, because of the occasional neglect of important details, corrosion incidents have occurred. The problems with single strand tendons can be easily and inexpensively avoided by the proper attention to details.
SHEATHING FOR THE STRAND
Be sure that the strand assembly is contained in a tight polymer sheath, preferably extruded over the strand. The sheath should be of uniform thickness, at least 0.04 inch, and preferably seamless. Within the sheath the strand should have a continuous coating of corrosion inhibiting grease.
CONCRETE COVER OVER TENDONS
Make sure that specified or required concrete cover is achieved within reasonable tolerances. It is preferable in an aggressive environment to have more cover.
ELECTRICAL ISOLATION OF TENDONS
Where the anchorage area is subject to a constant source of water, or in aggressive environments, consider the use of a tendon that is completely encased from end to end so that there is no direct electrical contact of the tendon with the concrete or any metallic elements embedded in it. This is called an electrically isolated tendon.