Is it practical to use a retarder to obtain selective bond between prestressing strands and the concrete in a beam?
A retarder called Lubabon has been developed for precisely this purpose. It enables the designer to locate the bond transfer point at any desired place along the length of the beam. In practice, of course, a material of this kind would be applied to the strands at the ends of the beam to prevent the development of excessive compressive stresses in the concrete. Allowable spans may in this way be increased by as much as 10 feet.