Manufacturing of concrete
Introduction
Production of concrete requires meticulous care at every stage The ingredients of good and bad concrete are same but good rules are not Observed it may become bad
Manufacturing of concrete includes the following stages
1. |
Batching |
2. |
Mixing |
3. |
Transporting |
4. |
Placing |
5. |
Compacting |
6. |
Curing |
7. |
Finishing |
Batching
The measurement of materials for
making concrete is known as batching. Methods of batching
Volume
batching
Weigh batching
Volume batching
The required ingredients of conc. Are measured by volume basis
o Volume
batching is done by various types of gauge boxes
o The gauge boxes are made
with comparatively deeper with narrow surface o Some
times bottomless gauge boxes are used but it should be avoided
Volume batching is not a good practice because of the
difficulties it offers to
granular material.
Some of the sand in loose condition weighs much less than the
same volume of
dry compacted soil.
For un important concrete or any small job concrete may be
batched by volume.
Weigh batching
It is the correct method of measuring materials for concrete.
Use of weight system in batching ,facilitates accuracy
flexibility and simplicity
The different types of weigh batching are there, they are used
based on the different
situation. In small works the weighing arrangement consist of
two weighing buckets
connected to the
levers of spring loaded dials which indicates the load,
The weighing buckets are mounted on a central spindle about
which they rotate
On large works the weigh bucket
type of weighing equipment used ,the materials are fed from the over head
storage hopper and it discharges by gravity.
Mixing
Thorough mixing of materials is essential for the production
of uniform concrete
The mixing should ensure that the
mass becomes homogeneous uniform in color and consistency.
·
Types of mixing
Hand mixing
Machine mixing
Hand mixing
It is practiced for small scale
un important concrete works. Hand mixing should be done over a impervious
concrete or brick floor sufficiently large size take one bag of cement. Spread
out and measure d out fine aggregates and course aggregate in alternative
layers.
Pour the cement on the top of it
and mix them dry by showel, turning the mixture over and over again until the
uniformity of color is achieved. The uniform mixture is spread out in the
thickness of about 20 cm. The water is taken and sprinkled over the mixture and
simultaneously turned over. The operation is continued till such time a good
uniform homogeneous concrete is obtained
Machine mixing
Mixing of concrete almost
invariably carried ot by machine ,for reinforced concrete work medium or large
scale concrete works .
Machine mixing is not only
efficient it is also economical when quantity of concrete to be produced is
large
Type of mixer for mixing concrete
1.
Batch mixer
2. Continuous
mixer
Concrete mixers are generally
designed to run at a speed of 15 to 20 revolutions per minute
For proper mixing it is seen that
about 25to 30 revolutions are required in a well designed mixer
It is important that a mixer
should not stop in between concreting operations for this requirement concrete
mixer must be kept maintained
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