Concrete is produced by combining basic materials like
cement, aggregate and water into a homogenous, suitably designed, plastic mix
that solidifies into structural and non-structural building members. The process
of production of concrete involves batching, mixing, transportation, placing,
consolidating and curing.
Concrete batching and mixing equipment
Concrete Weight Batching Equipment
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concrete mixer with attached weight batching
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Batching is the process of proportioning cement,
aggregate, water and admixture (where added), by weight (commonly used method)
or volume, prior to mixing. The equipment used for batching and mixing can be
divided into three categories, viz. mobile concrete mixers, commonly called
concrete mixers; centralized batching and mixing plant; and mobile truck-mixers
which are covered under concrete transportation.
Mobile concrete mixers
Tilting Concrete Mixer
These mixers have a conical or circular rotating drum
with baffle fittings inside. These are mounted on pedestals with facilities for
batching of various concreting materials. These are there types of concrete
mixers, viz. tilting drum mixers, non-tilting drum mixers and reverse drum
mixers. Tilting drum mixers discharge the concrete by tilting the drum. Tilting
drum mixers are used for producing very small quantities of concrete or mortar
mixes.
Non-Tilting Concrete Mixer
Non-tilting drums are suitable for requirements say up
to 10 m3/h. these have ah hopper-fitted outlet on the top for
loading and another chute-fitted outlet on the bottom for discharge. The reverse-drum
mixers mix on one direction and discharge in the opposite direction.
Mobile Concrete Mixer
The mobile concrete mixers vary in size from as slow
as 100 litres to 400 litres or more per cycle. The size of the concrete mixers
denotes the volume of concrete that can be mixed in a single cycle, and usually
it is expressed in cubic feet or cubic meters, or the ratio of the concreting
materials volume to the wet concrete volume, for example 21/14 means a concrete
mixer having maximum capacity to hold dry concreting materials up to 21 cubic
feet capable of producing wet concrete of 14 cubic feet.
Concrete mixers are available as static units and
trailer-mounted units.
The hourly output of a concrete mixer can be
calculated by multiplying production in m3 per batch or cycle into
the number of batches per hour. In the absence of actual data, for planning
purposes, the hourly output for various sizes of concrete mixers can be taken
as:
Hourly Output for various sizes of compact mixers
output of concrete mixers.
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Mixer size
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Batches/hour
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Output (M3/hour)
|
|
|
7/3.5
|
(100)
|
17
|
1.7
|
|
7/5
|
(140 litres)
|
16
|
2.3
|
|
10/7
|
(200 litres)
|
15
|
3.0
|
|
14/10
|
(280 litres)
|
14
|
3.9
|
|
21/14
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(400 litres)
|
12
|
4.8
|
|
32/21
|
(600 litres)
|
10
|
6.0
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Central batching plant
A central batching plant includes all types of
equipment and materials necessary to provide input to the mixers and to deliver
output to the concrete transporting system. Batching plants can be divide into
two categories, viz. medium size or low profile batching plants, and large
volume or high profile batching plants. Generally, medium size batching plants
have a rated capacity of 25 m3/h to 60 m3/h and are used
for producing concrete for building construction projects where as batching
plants having higher capacity, say 120 m3/h, are employed for heavy
construction or are used in the ready-mix concrete supply business.
Concrete Batching Plant
Experience dictates that for planning purposes, the
average output of the central concrete batching plants be taken as 60% to 70%
of hourly rated capacity for each working hour so as to cater for various
correction factors specially idle-time on account of non-utilization period and
repairs.
