RMC BATCHING PLANT
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PROCESS OF MANUFACTURE OF CONCRETE
Production of quality concrete requires meticulous care exercised at every stage of manufacture of concrete. It is interesting to note that the ingredients of good concrete and bad concrete are same. If meticulous care is taken at every stage, it will result in good concrete.
The measurement of materials for making concrete is known as batching. The types of batching are:
Volume batching is not a good method for proportioning the material because of the difficulty it offers to measure granular material in terms of volume. Volume of moist sand in a loose condition weighs much less than the same volume of dry compacted strength.
Because of this, for quality concrete materials have to be measured by weight only.
However, for unimportant concrete work or any small job, concrete may be batched by volume.
Weigh batching is the correct method of measuring the materials. For important concrete works, invariably, weigh batching system should be adopted. Use of weigh system in batching facilitates accuracy, flexibility and simplicity.
In modern batching plants the moisture content of the aggregates with the help of sensors and corrective action is taken to deduct that much quantity of water contained in sand from total quantity of water.
Thorough mixing of the materials is essential for the production of uniform concrete. The mixing should ensure that the mass becomes homogeneous, uniform in colour and consistency. There are two methods adopted for mixing concrete:
(1.) Hand mixing
(2.) Machine mixing
Hand mixing is practised for small scale unimportant concrete works. As the mixing is not thorough and efficient, it is desirable to add 10 % more cement to cater for the inferior concrete prepared by this method
Hand mixing should be done over impervious concrete or brick floor of sufficiently large size to take one bag of cement. Spread out the measured quantity of coarse aggregate and fine aggregate in alternate layers. Pour the cement on top of it, and mix them dry by shovel, turning the mixture over and over until the uniformity of colour is achieved. This uniform mixture is spread out in thickness of about 20 cm. Water is taken in a water can fitted with a rose-head and sprinkled over the mixture and simultaneously turned over. This operation is continued till such time a good uniform, homogeneous concrete is obtained.
Transit mixer is one of the most popular equipments for transporting concrete over a long distance particularly in RMC plant. There are over 600 transit mixers in operation in India. They are truck mounted having a capacity of 4-7m3. In a transit mixer, mixed concrete is transported to the site by keeping it agitated all along at a speed varying between 2-6 revolutions per minute.
PLACING OF CONCRETE
Construction formwork is the use of support structures to mould and set concrete that has been poured into moulds. The type of formwork that is used in a construction project is determined by many different aspects such as the height of a pillar, which will determine what type of materials will be used to create the specific mould wherein the concrete will be poured. These materials are normally stripped away from the concrete structure once the concrete has set but can also be left to form part of the structure. This type of formwork is known as stay-in-place formwork.
Today, RMC is playing a very important role in building road and civil structures. They offer unmatched rigidity and long life to the structure. Hence it is getting popular and the use is increasing day by day. There are many advantages of ready mixed concretes some of which are:
Less wastage of basic materials
Increased concrete quality
No labour required
Reduced noise and dust pollution
No storage space required for basic materials
Reduced required time