Post-Tension Slab

GEL is the pioneer of the post-tensioned slab system in Thailand since 1968. There are several million square meters such as parking building, condominium, commercial building, department store and other buildings which have structural height ranges from 1 up to 60 storeys. Post-tensioned slab can be designed the modern building with few columns at intervals and no beam between column, enabling an increase in number of floors and also making the construction become faster and more efficient.

Advantages of Post-Tensioned Slab

Allocate the elegant and comfort space

  • Space can be easily allocated since there is no beam to limit flooring span.
  • Utility space area can be adjusted according to functional variety.
  • M&E layout plan can be arranged easier since there is no beam to be the obstacle.
  • The buildings can be designed with longer span which make its space look more clear.

Structural Aspect

  • Post-tensioned slab provides flat and thin floor. The total weight is less than reinforced concrete (RC slab). Therefore, the construction cost of foundation work can be reduced.
  • Design process is considered about fire resistance of Post-tensioned slab by defining minimum fire resistance hours according to the instruction of Post Tensioning Institute (PTI).
  • The overall height of the building with the post-tensioned slab is less than the reinforced concrete slab (RC slab) in case the building has the same number of storeys. Therefore, the building can get the less effect of wind and earthquake forces.

Reducing construction costs and time

  • The height between floors is reduced. Thus, the building can be built more storeys with the same height, comparing to reinforced concrete slabs (RC Slab).
  • Save material storage area. The materials can be delivered to construction site and lifted to the working floor immediately. Additionally, building can be constructed in the limited area.
  • The height between floors is reduced. Vehicle ramp can be built with a short distance (vehicle ramp slope and length depending on the height between floors). Therefore, it can arrange more parking space.
  • Save construction time by taking 7-10 days for construction period of Post-Tensioned slab per floor
GEL is the pioneer of the first post-tensioned flat slab system in Thailand. We strive to keep looking for new system to improve our method of construction to be more efficient and effective.

General specification for post-tension slab

1. Concrete: Compressive strength of concrete cylinder should not be less than 240 ksc at stressing process and not less than 320 ksc at age of 28 days.

2. PC Strand : Seven-Wire Stress-Relieved Uncoated Strand Grade 270k with the diameter of 12.7 mm (1/2 inch), according to ASTM A-416 and TIS 420-2540

3. Bonded Tendon: The tendon must be strong to withstand vibration during pouring and vibrating concrete. Grouting process will be done by Portland cement type I.

4. Anchorage must be more than 95% of compressive strength and able to hold wire effectively throughout the life structure.


Step 1: Erect formwork for post-tension slab.

Step 2: Place bottom reinforcing steel bar.

Step 3: Lay tendon with PC strand.

Step 4: Set up the anchorage.

Step 5: Place top reinforcing steel bar.

Step 6: Pour concrete

Step 7: Stress PC strand

Step 8: Fill anchor socket after stressing

Step 9: Grout tendon with cement paste