Process of Manufacture

Processes of manufacture comprise a main process supplemented by an auxiliary process and a subsidiary process (Sharma, 1988).

1. Main Process

The activities involved in the main process are given below:

1. Providing and assembling the mould.
2. Placing a reinforcement cage in position on the reinforced concrete work and stressing the wires in the case of prestressed concrete elements.
3. Fixing tubes and inserts wherever necessary.
4. Placing the concrete in the moulds.
5. Vibrating the concrete and finishing.
6. Demoulding the forms, removing the units and stacking the products for curing.
7. Curing is done. Preferably steam curing may be resorted to.

2. Auxiliary Process

The activities affecting the successful functioning of the main process are as follows:

1. Mixing of proportionate ingredients and manufacture of fresh concrete which is done in a mixing station or by a batching plant.
2. Prefabrication of reinforcement cage is done in a steel yard or workshop.
3. Manufacturing of inserts and other finishing items needed for the precast units.
4. Taking on the job of finishing the precast products.
5. Arranging for the testing of these products.

3. Subsidiary Process

The activities that help to keep the main production unit functioning properly are as follows:

1. Storage of all the ingredients for concrete and other materials.
2. Arranging to transport cement, sand and aggregates.
3. Transporting the green concrete and reinforcement cages to the moulding yard.
4. Transporting the finished products to the stacking yard.
5. Undertaking all repair works, maintenance of tools, machines, etc.
6. Arranging to produce steam for curing.

4. Overall Management

For the successful running of the entire production unit, the following aspects should be properly exercised:

1. To ensure speed and economy while manufacturing concrete, a cyclic technological method has to be employed.
2. To improve quality and increase productivity, the mechanisation has to be improved.
3. Optimum production has to be achieved with quality elements produced.
4. To maintain speed to meet the supply.
5. Working conditions should be improved for the people on the job.
6. To minimize the interruption of production due to weather or other causes.

5. Methods of Manufacturing

There are two methods of manufacturing precast concrete units, viz., the Stand Method and the Flow Method.

In the Stand Method, the moulds are stationary and remain at one place, where the various processes involved are carried out in a cyclic order at the same place.

In the Flow Method, the precast units under consideration are in movement from one place to another in a cyclic order according to the various processes involved in the work.