Post-Tensioned Concrete
CSI Division 03, Concrete
A concrete construction method where steel tendons are threaded through ducts cast into a slab or beam and then stressed, tensioned, and anchored after the concrete cures, putting the concrete permanently into compression, distinct from conventional [[concept-rebar|reinforced concrete]], which simply resists tension passively as the structure is loaded.
Why it matters
Because the tendons are stressed to specific, engineered forces after the pour, the stressing sequence and timing are safety-critical: concrete has to reach a minimum strength before stressing begins, and an under-strength pour stressed too early risks a tendon anchor pulling through the concrete.
On a real project
A parking structure's post-tensioned slab is stressed by a specialty PT subcontractor only after concrete cylinder breaks confirm the slab reached its required minimum compressive strength, following a stressing sequence the structural engineer specified.
Who this matters most to
A Structural Engineer designs the tendon layout and required stressing sequence. A Concrete Worker or specialty PT crew places and stresses the tendons.
Where this goes wrong
A PT crew begins stressing tendons ahead of schedule to keep the job moving, before the concrete's cylinder breaks confirm it reached the required strength. An anchor pulls partially through the still-undercured concrete, requiring the structural engineer to evaluate and repair the slab before it can be safely loaded.