The concrete is placed as close as possible to its final position to avoid segregation. The placed concrete is then fully compacted to expel the entrapped air, and the next layer of concrete is laid while the underlying layer is still in the plastic state. The rate at which concrete is placed and compacted is kept equal.
While placing concrete, care is taken to ensure that the concrete is laid in uniform layers, and hand shoveling and moving concrete using poker vibrators is avoided. Also, considerable delays in filling concrete in the forms for vertical structures lead to the formation of cold joints. When placing concrete in deep sections, collision with formwork or reinforcement is avoided, and for inclined surfaces, concrete is placed in vertical planes against the preceding layer.
Methods like chutes, buggies, conveyor belts and pumping concrete using pipes are commonly used for placing concrete. However, specific situations may require advanced techniques. Tremie concreting, suitable for deep and underwater placements, involves a vertical pipe with water-tight seals that allow concrete to flow by gravity. As concrete is placed, the pipe is lifted while its end remains immersed in the concrete, preventing any water intrusion. In contrast, the slip-forming technique is used for continuous placement and compaction of concrete in vertical structures. Forms steadily move upward as the concrete sets, allowing for rapid construction.
The slip-forming technique enables the continuous placement and compaction of concrete by moving forms steadily as the concrete sets.
