CONCRETE BATCHING PLANT
The working principle is dependent on 5 main functions.
Aggregate feeding: It means that aggregates and sand have to be fed to the feeding unit.
Binder feeding: Binder refers to cement, fly ash, additive materials that will help to bond the material.
Water feeding: water is important component. A fixed quantity of water as per the recipe will help bind
the ready mix material.
Storage: Storage here refers to the storage of cement, fly ash, etc. These materials are stored in different
storage compartments. They are weight into weighing hopers and then added into mixing unit.
Controls: plant control panel is important component and it is responsible for controlling the working of
the plant.
First the aggregates are fed into the feeder bins as per their sizes. They are weighed one by one by a
weighing conveyor which is suspended on load cells. This weighing conveyor is just blew the feeder bins.
As soon as the weighing is done the aggregates are transferred to the mixing unit.
On top of the mixing unit there is weighing hoppers for cement, water and additives. These weighing
units will weigh respective items prior to discharging the same into the mixing unit. Once inside the
mixing units all the items will be mixed uniformly for fixed duration. Water is transferred to the weigh
hopper by water pump. Cement is transferred to the weigh hopper by screw conveyor. Then the concrete
mix is poured to truck mixer.
TRUCK MIXER
Truck mixers are the most common mode of concrete transport. They consist of a truck mounted
drum that rotates on an inclined axis. Mixing drums contain helical blades on their inside walls that
are designed to push concrete to the bottom of the drum when rotates in the opposite or discharge
direction. Most truck mixers discharge to the rear; however, front discharging truck mixers are
gaining popularity because the driver can drive directly on to a site and mechanically control the
positioning of the discharge chute without the help of contractor personnel.
Agitation
Drum rotation is used for two purposes: mixing and agitation. High speed rotation is used to mix concrete
ingredients in to a homogenous material. This type of mixing typically takes between 50 and 100
revolutions depending up on pcc characteristics and environmental factors. Low speed rotation about
2rpm is used to agitate the pcc to
1. Maintain its homogeneity
2. Prevent slump loss while in transit.
Truck mixers are equipped with a revolution counter to help maintain tight control over the total number
of drum revolutions. Mixing which is generally short in duration is usually planned for specific time or
place. If not mixing, truck mixers usually operate in the low speed agitation mode. Mixing is typically
done using one of the following three methods.
1. Mixing at the batching facility: The drum is turned at high speed(12-15 rpm) for about 50 revolutions
while at the production facility, which allow for quick check of batch characteristics .The pcc is then agitated(<2
rpm) while in transit to the paving site.
2. Mixing in transit: The drum is turned at medium speed(about 8 rpm) for 70 revolutions while driving to the
job site. The pcc is agitated (<2 rpm ) until discharge.
3. Mixing at the paving site: The pcc is agitated (<2 rpm) while in transit to the paving site. Upon arrival, the
pcc is mixed (12-15 rpm) for 70 to 100 revolutions, or about 5 minutes.
In general, short times between mixing and placement can better avoid problem of premature hardening
and slump loss that results from potential delays in transit. Regardless of the mixing mode pcc is a perishable
construction material.
BEDILU TEGEGNE
ETE/1698/07
Masonry (noun) is the building of structures from individual units, which are often laid in and bound
together by mortar; the term masonry can also refer to the units themselves. The common materials of
masonry construction are brick, building stone such as marble, granite, and limestone, cast stone,
concrete block, glass block, and adobe. Masonry is generally a highly durable form of construction.
However, the materials used, the quality of the mortar and workmanship, and the pattern in which the
units are assembled can substantially affect the durability of the overall masonry construction. A person
who constructs masonry is called a mason or bricklayer. These are both classified as construction trades.
Applications
Veneer masonry
Dry set masonry
Brick
Concrete block Edit
Concrete masonry units (CMUs) or blocks in a basement wall before burial.
Blocks of cinder concrete (cinder blocks or breezeblocks), ordinary concrete (concrete blocks), or hollow
tile are generically known as Concrete Masonry Units (CMUs). They usually are much larger than
ordinary bricks and so are much faster to lay for a wall of a given size. Furthermore, cinder and concrete
blocks typically have much lower water absorption rates than brick. They often are used as the structural
core for veneered brick masonry, or are used alone for the walls of factories, garages and other
industrial-style buildings where such appearance is acceptable or desirable. Such blocks often receive a
stucco surface for decoration. Surface-bonding cement, which contains synthetic fibers for reinforcement,
is sometimes used in this application and can impart extra strength to a block wall. Surface-bonding
cement is often pre-coloured and can be stained or painted thus resulting in a finished stucco-like
surface.
The primary structural advantage of concrete blocks in comparison to smaller clay-based bricks is that a
CMU wall can be reinforced by filling the block voids with concrete with or without steel rebar.
Generally, certain voids are designated for filling and reinforcement, particularly at corners, wall-ends,
and openings while other voids are left empty. This increases wall strength and stability more
economically than filling and reinforcing all voids. Typically, structures made of CMUs will have the top
course of blocks in the walls filled with concrete and tied together with steel reinforcement to form a bond
beam. Bond beams are often a requirement of modern building codes and controls. Another type of steel
reinforcement, referred to as ladder-reinforcement, can also be embedded in horizontal mortar joints of
concrete block walls. The introduction of steel reinforcement generally results in a CMU wall having
much greater lateral and tensile strength than unreinforced walls.
"Architectural masonry is the evolvement of standard concrete masonry blocks into aesthetically pleasing
concrete masonry units (CMUs)."[2] CMUs can be manufactured to provide a variety of surface
appearances. They can be colored during manufacturing or stained or painted after installation. They
can be split as part of the manufacturing process, giving the blocks a rough face replicating the
appearance of natural stone, such as brownstone. CMUs may also be scored, ribbed, sandblasted,
polished, striated (raked or brushed), include decorative aggregates, be allowed to slump in a controlled
fashion during curing, or include several of these techniques in their manufacture to provide a decorative
appearance.[3]
"Glazed concrete masonry units are manufactured by bonding a permanent colored facing (typically
composed of polyester resins, silica sand and various other chemicals) to a concrete masonry unit,
providing a smooth impervious surface."[4]
Glass block or glass brick are blocks made from glass and provide a translucent to clear vision through
the block.
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