What is curing?
Curing can be defined as keeping the concrete moist
and warm enough so that hydration of cement can continue. It is the process of
maintaining satisfactory moisture content and a favourable temperature of
concrete during the period immediately after placing, so that hydration of
cement continues until the desired properties develop to the required degree.
If curing is neglected in the early period of
hydration, the quality of concrete experiences irreparable losses. For preparing
good concrete, curing is an important as other criteria such as mixing,
vibrating and placing of concrete.
Methods of curing
Water curing
This is the best method for curing. Water curing can
be done in the following ways:
Immersion
The pre-cast concrete items are normally immersed in
curing tanks for the required duration.
Ponding
Floor slabs, rods, slabs etc. are covered by water by
making small ponds of water.
Spraying and Wet Covering
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Vertical retaining walls and concrete columns are
cured by spraying water. In some cases, wet coverings such as wet gunny bags,
Hessian cloth etc. are wrapped around the vertical surfaces for keeping the
concrete wet.
Membrane curing
During acute shortage of water, it is not possible to
cure the concrete with ample quantity of water. In such cases membrane curing
is done. The basic concept behind membrane curing is that the water used to mix
the concrete is not allowed to go out from the body of concrete, obviously,
this water helps in uninterrupted and progressive hydration.
Application of heat
When concrete is subjected to higher temperature along
with moisture, it accelerates the hydration process, resulting in the
development of strength.
For this the following process are found useful.
Steam curing at ordinary and high pressures.
Curing by Infra-red radiation.
Electrical curing.
Miscellaneous methods
Applying calcium chloride on the surface of the
concrete member is useful for effective curing. Calcium chloride is a salt and
shows affinity for atmospheric moisture retaining it at the surface.
In case of beams and columns, form-work prevents the
moisture from escaping the concrete, thus promoting hydration of concrete.
