When a freshly made concrete is placed inside its form or mould, it is necessary to compact this concrete properly to remove air voids, increase the density of the concrete and improve its strength. This compaction can be done manually using tamping rods or boards especially for small jobs. For more effective compaction, mechanical equipment such as poker vibrator is often used for the purpose. Poker vibrators consist of a hollow steel tube casing in which is a rotating impeller which generates vibrations as its head comes into contact with the casing.
Effective compaction of concrete using poker vibrator required that it is properly used. Figures 1 and 2 below shows how to properly use poker vibrator for compaction of concrete.
In essence poker vibrators should be inserted vertically and allowed to penetrate 75 mm into any previously vibrated concrete.
Adapted from Building Construction Handbook by Roy Chudley and Roger Greeno
