Placing of concrete
Concrete must be placed in a systematic manner to yield optimum results. Some situation here we used provide concrete. Placing concrete within earth mould Placing concrete with large earth mould or timber plank form work. Placing concrete in layers with in timber or steel shutter, Placing concrete with in usual form work,Placing concrete under water.
Placing concrete within earth mould
Concrete is invariably as foundation bed below the walls and columns Before placing concrete
o All loose earth must be removed o Roots of trees must be cut
o If surface is dry must be made just damp
o If it is too wet or rain soaked the water slush must be removed
Placing concrete with large earth mould or timber plank form work
For construction of road slabs,air field slabs and ground floor slabs in building conc os placed in this method. The ground surface must be free from loose earth pool of water ,grass or roots or leaves. The earth must be compacted well Poly ethylene film is used in between conc ground to avoid absorption of moisture. Concrete is laid alternative layers to give enough scope for shrinkage.
Placing concrete in layers with in timber or steel shutter
This can be used in the following cases
Construction of concrete abutments
Raft for a high rise building
The thickness of layers depend on
Method of compaction
Size of vibrator
Frequency of vibrator used
It is good for laying 15 to 30 cm thick layer of concrete ,for mass concrete it may varie from 35 to 45 cm. Its better to leave the top of the layer rough so that succeeding layer can have the good bond.
Placing concrete with in usual form work
This can be adopt for Column ,beam and floors Rules that should be followed while placing the concrete.
· Check the reinforcements are correctly tied and placed
· Check the reinforcement is having appropriate cover
· The joints between plywood's or sheets properly plugged
· Mould releasing agent should be applied
The concrete must be placed very care fully a small quantity at a time so that they will not block the entry of subsequent concrete
Placing concrete under water
Concrete is often required to be placed under water or I a trench filled with slurry. In such a cases use of bottom slurry buckets or termic pipes are used. In the bottom bucket concrete is taken through water in a water tight box or bucket reaching final place of deposition. The bottom is made to open by some mechanism and the whole concrete is dumped slowly.
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