Concrete, concrete everywhere and not a compactor in sight! When will the users of this wonderful, essential and highly versatile material realise that concreting does not end with placing?

Any primary text book on the material will tell you that the whole concreting process starts with batching and goes through mixing, transporting, placing, compacting, finishing and curing. Missing out on any one of the processes or following incorrect procedure in any one of these stages will affect concrete strength.

The ‘potential’ strength of concrete is measured through the casting of cubes which are taken from the mix to be used and are thoroughly compacted and then cured for 28 days prior to crushing.

So much for the layman’s belief that the ‘actual’ strength of the concrete on site (which can rarely be compacted and cured in the same manner) should be equivalent to this ‘potential’ strength as determined from cube samples.

This is well nigh impossible even given the best of work practices – and thus one cannot but imagine the results in the case of malpractice. The aim of compaction for example is to remove entrapped air from the concrete and not to fill the form – suffice it to say that one per cent entrapped air (only removed by compaction) is equivalent to five per cent loss in concrete strength.

Couple this with lack of adequate (if any) curing and the end results will speak for themselves.