4. Concrete clamping with energy input

To achieve satisfactory molding of traditional concrete, its adhesion to reinforcement, and develop its optimum mechanical resistance and durability characteristics, it is necessary to apply an intense means of clamping. This is usually achieved by high-frequency vibration of the fresh concrete (except in the case of self-placing concretes) introduced into the mold.

During this vibration, each concrete grain is subjected to amplitudes and accelerations that cause them to move relative to one another. The forces of adhesion and friction are reduced, and excess water and air can be released. The movement of pebbles modifies the support bases of the upper layers and, under the action of gravity, causes the concrete to settle and tighten (figure 10 ).