How to prepare good quality concrete?

How to prepare good quality concrete?

The concrete as such is a hetereogeneous material and hence it would assume a wide range of properties, if produced without exercising any control. For preparing a high quality concrete, the field organisation may broadly be divided into the following three divisions:

1. The engineering division which provides lines and grades and makes the initial inspection of all forms, reinforcement and installation of all embedded parts. 

2. The manufacturing division which exercise control over concrete materials, batching and mixing. 

3. The placing division which is concerned with the control of concrete placing and of related operations prior and subsequent thereto.

The concrete produced at site should be strong, dense, workable and economical for the job for which it is prepared. The amount of cement should be low and that of aggregates should be high. The most economical concrete with the highest possible density is obtained by observing the following general requirements:

1. The air bubbles should be of the smallest size. 

2. The cement particles should be of the smallest size.

3. The concrete would be compacted fully so as to remove voids.

4. The concrete should be cured sufficiently and adequately, say for 28 days.

5. The cubical particles of the aggregate should be used so that good interlocking is gained.

6. The water-cement ratio should be kept low.

The quality control of concrete demands a high degree of awareness among the personnel connected with the production of concrete, namely, supervisors, labours, etc. regarding the factors which influence the quality of concrete such as adding of water, cleanliness of various ingredients, adequate curing, etc. It therefore, becomes necessary to train such personnel for getting concrete of high quality. In a similar way, the engineer in charge of the work should have sufficient knowledge about proper working and maintenance of equipments used in producing concrete such as concrete mixers, vibrators, batching plant, etc.

The quality control aspects of concrete is of utmost importance and extreme is to be exercised at every stage of concrete production so as to obtain the desired results. The quality control, if propoerly achieved, grants the following advantages:

1. It helps in improved utilization of scarce resources and in extended utilization of low grade materials.

2. It helps to minimize failure.

3. It results into lower costs of construction as higher stresses can be assumed.

4. The structure becomes durable with lower costs of maintenance.