TR

Concrete Casting

Information About Concrete

"During the casting of ready-mixed concrete, the responsibility of the manufacturer vanishes as it delivers the transit-mixed concrete to the user at the discharge chute or chute pump of the transit-mixer. All subsequent works (placing, compacting, surface finishing and curing) to be carried out are at the responsibility of the user.

The user should pay attention to some important points in order to achieve the performance expected from the concrete casting.

Points to consider before casting the concrete:  

Measures should be taken with regards to vehicles, iron and sand heaps, electrical wiring, telephone cables, etc. in the vicinity of the casting site, which may prevent the operation of the ready-mixed concrete equipment, and a comfortable working environment should be provided.

  • The ground on which the pumps and transit-mixers will operate should be sufficiently firm to prevent subsidence and mudflow.
  • All formwork should be completed. The forms should be solid, light-tight, smooth, clean, and lubricated with formwork oil. The falsework should be made solid.
  • All reinforcement works should be completed. The reinforcement should be checked and fastened not to move during casting.
  • Attention should be paid to concrete covers and measures should be taken in order for the concrete covers not to be impacted during casting.
  • Sufficient number and quality of crew and equipment should be available for casting. In particular, the vibrators should be ready along with their spare parts and in working condition.
  • The preparations (water, hose, covers, etc.) for curing to be carried out after casting should be completed beforehand.
  • If concretes such as field concrete, road concrete and ground concrete are to be casted, the floor should be well compacted and wetted sufficiently (to a depth of 15 cm).

Points to consider during concrete casting:

After all preparations are completed, the most important step is the concrete casting. Placement of concrete into forms depends on the location of the structure.
The point where the concrete is to be casted should be the location, where the concrete will be placed. Concrete can be spreaded up to 3 m from the point where it is casted.
Concrete should be casted as horizontal layers as much as possible. Layer thicknesses should be equal and homogeneous in each region.

  • The concrete should be casted from a height of 1.5 m at the most when casted freely.
  • The main objective in casting the concrete should be non-segregation and preservation of the homogeneity.
  • The concrete should always be casted in a vertical direction and perpendicularly to the formwork.
  • Concrete casting should be performed continuously and without any interruption. Cold joints should not be allowed to be formed. For this reason, the casting speed should be well planned and implemented as such.
  • During the casting, physical impacts on the formwork and reinforcement should be avoided.
  • The compacting (vibration) and surface finishing processes should be carried out sequentially and in concert with one another during the placement of the concrete.
  • The concrete immersion vibrator should be immersed perpendicularly to the concrete surface that is to be compacted.
  • If the concrete of a thick-sectioned constructional component is to be compacted, the layer thickness should be between 30-70 cm.
  • The immersion range should not exceed 40-60 cm depending on the impact radius of the vibrator.
  • Immersion should be done very fast, the concrete immersion vibrator should be kept inside the concrete for about 5-15 seconds depending on the consistency of concrete and should be retracted slowly. The retracting speed should be approximately 8 cm/sec.
  • Formation of a very thin grout layer on the surface indicates that the compacting is successfully completed.
  • If the concrete is to be compacted in the form of layers, then the vibrator tip should be immersed from the top, up to a depth of 1/3 of the layer that lies underneath, and both layers should be fused as such.
  • The vibrator should not be contacted with the surface of the formwork.
  • When operational, the vibrator tip should not be contacted with the reinforcements. 
  • Surface finishing is the final process to be carried out when the concrete is still in the form of a fresh concrete.
  • Surface finishing should be done in a timely manner and in the form of plaster strips.
  • The plastic shrinkage cracks that may occur following the surface finishing process should be covered with a second surface finishing.
  • Curing of the concrete should be started immediately especially in constructional components with large surface areas."