Placing & Compacting of Concrete

Reinforcement is the only additional item that differentiates R.C.C( Reinforced Cement Concrete) from P.C.C(Plain Cement Concrete). Generally, the size of coarse aggregates in R.C.C is 20mm. Else concrete mixing ratio, method of mixing and curing is same to that used for plain cement concrete.

In case of R.C.C, concrete should be such that it easily settled down in the reinforcement cage without segregation of aggregates. If vibrator is used for concrete compaction, then water to cement ratio should be different.

Slump test is carried out for setting out the limits of concrete workability and consistency. Set limits depend on the nature of work. Following are the limits of slump depending on type of work;


Nature of Concrete Work           

Slump With Vibrator

Slump Without Vibrator

Heavy Concrete Works:Dam, Retaining Wall and foundation work



Beam, Slab and Column


100 to 125 mm

Thin Sections of R.C.C:Excessive use of steel

40 to 50mm

125 to 150 mm


Compacting of Concrete

After laying of concrete on form work, instant compaction should make possible. Vibrator should be used for concrete compaction. In case arrangement of vibrator is not possible, then use steel tamping rod of 16mm diameter for compaction. Continue the compaction of concrete till it settled down at every corner of form work.

Use of slurry on the final concrete surface makes concrete surface plain by filling the voids. One thing must be noted that compaction of concrete should be done before the beginning of concrete initial settling time.

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