Mechanical Compaction:

In case of mechanical compaction concrete is compacted by vibration during which the vibrator communicates rapid vibrations to the particles thus increasing the mobility of concrete. The particles occupy a more stable position under the force of gravity. The concrete combine fills all the spaces thus forcing air to the surface and making concrete denser. The frequency and duration of vibration, its amplitude totally depends on the conditions of vibration for compacting the mix. A maximum frequency of vibration depends on the size of the particles and on the mobility of concrete. Following are the advantages of vibratory compaction.

(a) A better quality and better finish of concrete is obtained as compared to hand compaction.

(b) The concrete produced is more dense and impermeable.

(c) Bond among steel and concrete is improved.

(d) Laitance is partially reduced.

(e) Speed of placing concrete is raise by the ready flow of vibrated concrete into difficult positions.

(f)  Creep and shrinkage are also decreased because of the possibility of higher aggregate-cement ratio.

(g) Concrete along with even lower w/c ratio and with lower cement can be compacted effectively.

(h) Better compaction could be achieved in heavily reinforced concrete members.

The subsequent difficulties are encountered in vibratory compaction.

(a) Finishing of horizontal surface.

(b) Discharging extremely stiff concrete from mixers.

(c) The lack of enough vibration at points not immediately in contact with the vibrating equipment thus resulting in segregation.

(d) An Discharging stiff concrete from Lorries and other means of transport.