Methods of compation of concrete

Vibration:

To compact concrete you apply energy to it so that the mix becomes more fluid. Air trapped in it can then rise to the top and escape. As a result, the concrete becomes consolidated, and you are left with a good dense material that will, after proper curing, develop its full strength and durability.

Vibration is the next and quickest method of supplying the energy. Manual techniques such as rodding are only suitable for smaller projects. Various types of vibrator are available for use on site.

Poker Vibrators

The poker, or immersion, vibrator is the most popular of the appliances used for compacting concrete. This is because it works directly in the concrete and can be moved around easily.

Sizes:

Pokers with diameters ranging from 25 to 75mm are readily available, and these are suitable for most reinforced concrete work. Larger pokers are available - with diameters up to 150mm - but these are for mass concrete in heavy civil engineering.

Radius of action:

When a poker vibrator is operating, it will be effective over a circle centred on the poker. The distance from the poker to the edge of the circle is known as the radius of action.

However, the actual effectiveness of any poker depends on the workability of the concrete and the characteristics of the vibrator itself. As a general rule, the bigger the poker and the higher its amplitude, the greater will be the radius of action. It is better to judge from your own observations, as work proceeds on site, the effective radius of the poker you are operating on the concrete you are compacting.

The length of time it takes for a poker vibrator to compact concrete fully depends on:

1.                  The workability of the concrete: the less workable the mix, the longer it must be vibrated.

2.                  The energy put in by the vibrator: bigger vibrators do the job faster.

3.                  The depth of the concrete: thick sections take longer.