Post-tension site supervision by the design engineer

A post-tensioned slab is only as good as the tendons that end up in the concrete. The design assumes a profile, an anchorage zone and a stressing sequence; site supervision checks that what is built matches those assumptions before the concrete makes them permanent. Iron Axis provides that check as a specialist engineer, engaged by the consultant, the developer, the main contractor or the PT specialist contractor itself.

Because the supervising engineer also designs PT slabs, the inspection is done against the intent of the design, not only against a checklist. When a duct clashes with a service sleeve or a column cage, the question on site is not just "is it within tolerance" but "does the redistributed profile still carry the load". We can answer that the same day.

Pre-pour inspection

• Tendon profiles — chair heights against the shop-drawing profile at high points, low points and inflection points, and smooth transitions without kinks.
• Tendon positions and spacing — banded and distributed tendons, minimum spacing, deviations around openings and penetrations, and the number of strands per tendon.
• Anchorages — live and dead end anchors square to the tendon, pocket formers, bursting reinforcement and the edge distances shown on the drawings.
• Sheathing and ducts — damage to unbonded tendon sheathing, duct joints and vents for bonded systems, and protection of anchorages at construction joints.
• Coordination — clashes with MEP sleeves and embedded conduits, top and bottom reinforcement, punching shear reinforcement and the pour strip layout.

During and after the pour

We review concrete strength results against the transfer strength set in the design before stressing is allowed, witness stressing when required, and review the stressing records against the calculated elongations. The detail of that last step is on our stressing supervision and elongation records page.

On many projects the PT design, the materials and the site work come from the same specialist contractor. That can work well, but it means the party checking the work is the party doing it. A dedicated PT supervisor gives the consultant of record and the client a second set of eyes that has no stake in the tendon quantity or the programme.

Typical problems we look for are the ones that are expensive to find after the pour: profiles flattened by foot traffic, chairs missing at low points, anchorages set at an angle, tendons pushed out of the band to clear a sleeve, and missing bursting steel. Each finding is recorded with a photograph, a location on the drawing and a clear instruction, and closed out before the pour is released.

Site attendance is available in Dubai and the Northern Emirates and, by arrangement, in Abu Dhabi. For projects in Saudi Arabia, Qatar, Oman, Bahrain and Kuwait, we combine planned site visits with remote review of photographs, survey data and stressing records. The level of attendance is agreed in writing at the start, so everyone knows which pours are inspected in person.

Iron Axis is a design and supervision practice. We do not provide PT materials or installation labour, so the supervision stays focused on quality and compliance.