Post Tensioning – Process

LAYING:

* Completion of formwork as per shop drawing.

* Check level difference; pour strip location, slab thickness and drop panel depth before erection of bottom reinforcement.

* Completion of bottom reinforcement with appropriate Dia of bar and with equal spacing.

* Fixing the block out to casting and wrapping it with OPP tape.

* Marking of tendon in both live and dead end with marker.

* Anchorage should be fixed to the mark at end form work by supporting bars.

* Laying of GI duct is under progress.

* Fixing of duct to end anchorage with the help of vent coupler and it should be wrapped with OPP tape to avoid entry of foreign particles.

* De – coiling of HT Strand and cutting the strand for required size of the tendon.

* Inserting the strands to the duct.

* Check C.G of the casting.

* Bursting reinforcement should be fixed to position at end anchorage

* Profile chair should be fixed to the tendon as per shop drawing.

* Fixing of grout hose in both live and dead end. If the span is more than 35m intermediate vent hose should be provided.

* Proper packing of casting to avoid entry of foreign particle.

* Pouring of concrete (M-35 Grade).

* Proper vibration of the member @ face of the anchorage.

STRESSING

* Concrete should attain minimum strength of 28N/mm2

* Removal of block out.

* Fixing of wedge Plate and wedges.

* 25% of initial load for slack removal.

* Mark each strand with help of the marker

FLAT TENDON

* Stress the strand for final loading as per stressing calculation report.
* Ensure Protruding strand length is sufficient for stressing (350 – 400mm)
* Stress of tendon is done by (T-25 Jack) as it can stress only one strand at a time.
* Elongation for each strand should be checked after 24hrs.

MULTI TENDON

* Multi jack should be hoisted with chain pulley.
* All strands should be inserted to jack guide pipe.
* Ensure the strand is locked to jack pulling head.
* 25% of initial load for slack removal.
* Record the strand elongation for every incremental of 10 Mpa.
* Release the pressure when the jack has reached desired load.

GROUTING

* Mix the grout as per grout mix.
* The mix is prepared with W/C ratio of 0.4 – 0.45 as per site condition with additive of 0.2% (Weight of the cement).
* Inject the grout from tendon inlet hose.
* As the grout flows out of the intermediate vent, lock these vents in the direction of grout.
* Lock the outlet hose when the grout flows out.
* Check the grout pumped out has the same consistency as its pumped in.
* Lock the inlet hose when the required pressure is achieved (3-5 bars).

Construction sequence