What is batching, mixing, transporting, compacting and curing.

Explain briefly the terms batching, mixing, transporting, compacting and curing.

 
Batching :-
Bathing in concrete refers to accurate measurement of material 
used in the production of concrete. The constituents of concrete are 
measure with the following tolerance 

limits:
Aggregate, cement, water - +3% of batch quantity 
Admixtures - +5% of batch quantity

•  Batching may either be manual, semi-automatic or automatic.

•  Manual batching is allowed for small and un-important construction jobs.

•  In semi-automatic batching, the aggregate bin gates are opened by manually operated switches. The gates get closed automatically when required weight has been delivered.

•  In automatic batching, materials are operated electronically by a single switch.

Mixing :- 
Mixing is done so as to have a uniform mass of concrete and to 
coat all the aggregate surfaces with the binder (i.e. cement).

•  Concrete mixing is done in a mixer.

•  In the mixing process, firstly the cement paste is formed with simultaneous absorption of water in the aggregates. Subsequently, the cement paste coats the aggregate particles.

•  After the mixing process gets over, it appears to be of uniform color and grading.

Transporting concrete :-
Concrete from the mixer is transported to the 
place where it is required as soon as possible otherwise segregation or setting of concrete takes place.

•  Specifications permit a maximum time of two hours between the addition of water to the cement and aggregates sand the discharge provided concrete is transported in a truck mixer or in an agitator.

•  In the absence of agitator, this time is reduced to one hour only.

•  However concrete when poured in the form-work should have a temperature of not less than 50C and not more than 320C.

Compacting concrete :-
 Air gets entrapped during the mixing and transportation process. If entrapped air is not removed then segregation of concrete may take place. The process of removal of entrapped air so as to have a uniform placement of concrete in a dense homogeneous mass is called as compaction of concrete.

1.  Even 5% voids in hardened concrete may reduce the strength of concrete by about 35%.
2.  Inadequate compaction leads to honey combing in the surface of concrete.
3.  A badly honey-combed concrete does not allow the bond the bond to get develop between the concrete and the reinforcement thus reducing its strength.

Curing of concrete :-
 It is the process of creation of an artificial 
environment in a relatively short period immediately after the placing 
and compaction of concrete which aids in setting and hardening of 
concrete.

•  The presence of sufficient moisture makes up for the loss of moisture due to evaporation from the concrete.

•  The concrete continues to gain strength is sufficient moisture is available for the hydration of cement.