Re-Fab LLC’s unbonded monstand post-tension system is easily adapted to many different types of structures that can be quickly installed in a cost-effective manner.
Concrete construction applications for our monostrand systems include elevated slabs, beams and transfer girders, shear walls, joists, slab-on-grade and mat foundations. Post-tensioning allows for thinner slabs, fewer beams, longer clear spans and more slender, dramatic elements. Thinner slabs mean less concrete is used in each structur. In addition, it means a lower overall building height for the same inside floor-to-floor height. Post-tensioning can allow a dramatic reduction in building weight versus a typical concrete building with the same amount of floors. This also reduces the foundation load and is a major improvement in seismic areas. A lower building elevation can also translate to substantial savings in mechanical systems and façade costs.
An unbonded monostrand post-tension tendon is comprised of two main components; the special 7 wire steel strand and the anchors at the ends of the tendon. The steel strand is a special 270 ksi cable consisting of 6 wires twisted in a helical pattern around 1 center wire known as the "king" wire. This strand is coated with specially formulated post-tension grease and covered with a seamless extruded plastic covering in a continuous process. After the concrete has been placed; it bonds to the plastic sheathing on the tendon; the steel cable is free to move as a result of the grease inside the tendon which also provides corrosion resistance. The anchorage systems on the ends of the tendon are comprised of machined heat treated wedges and ductile cast steel anchors. The hardened steel wedge fits inside of a conical hole in the anchor gripping the softer prestressed steel. This provides a permanent mechanical bond at the anchoring sites.
Encapsulated unbonded monostrand post-tensioning systems are also available and are used in areas that are subject to corrosive conditions. All of the strands are protected at the anchorage sites by using grease-filled end caps and greased plastic sleeves. In addition, all anchorage components are fully encapsulated in a high density polyethylene plastic covering; an optional encapsulated intermediate coupler anchorage system is used to protect the strand at construction joints.
For all jobs produced each tendon is accurately cut, coiled, labeled, color-coded and delivered to the job site. A bare or encapsulated anchorage system is available for each job to meet design specifications.