Common concrete probems and their prevention methods

archdevil

Elite Member
Sep 21, 2017
269
368
India
#1
COMMON CONCRETE PROBLEMS AND THEIR
PREVENTION:
There are many problems we might be facing
during and after
concreting. To produce high quality concrete
we must take
some precautions to avoid those common
problems during
concreting. In this article, we will discuss on
common concrete
problems and how to prevent them.
A) BLEEDING:
Bleeding refers to as a tendency of water to
appear on the top
surface of concrete after finishing. Due to
bleeding some
measure of water (with sand particles and
other cementing
materials) appears at the surface of the
concrete.
Following precautions should be taken to
reduce bleeding in
concrete.
1. Design the mix appropriately.
2. Include least water content in the mix.
3. Use greater amount of cement content.
4. Use greater amount of fine particles.
5. Utilize a little measure of air entraining
admixture.
B) SEGREGATION:
Segregation means separation of coarse
aggregates from the
concrete surface due to poor compaction. It is
generally seen in
the plastic stage of concrete. As a result
honeycomb, laitance,
scaling, porous layer, bond failure etc. can be
formed in
concrete. Following precautions should be
adopted to prevent
segregation in concrete.
1. Design the mix appropriately.
2. Never use excessive water content.
3. Take care of handling, placing, and proper
compaction of
concrete.
4. Do not allow the concrete to be dropped
from more heights.
5. Use air entraining admixture.
6. Keep the formwork to be watertight.
C) LAITANCE:
The appearance of cement-sand particles on
the surface of
freshly placed concrete is known as laitance.
It
is mainly
occurred due to the bad effect of bleeding
and
segregation of
concrete. The bond between subsequent
layers
of concrete
becomes weaker and as a result, laitance is
developed.
Following precautions can be taken to stop
the
occurrence of
laitance in concrete.
1. Clay, dust, silt content etc should be
removed before mixing
the concrete.
2. Water-cement ratio should be maintained
properly.
3. Water should not be sprayed on the
concrete surface during
finishing work.
4. Use well graded fine aggregates in the mix.
5. Add little amount of water reducing
admixture in the concrete
mix.
D) SCALING:
Scaling is the physical deterioration of
concrete in which the
surface layer of concrete broke down, pitted
or
flaked away.
Due to this effect concrete surface becomes
worse. Scaling can
be prevented by taking same precautions
adopted for laitance.
E) PLASTIC SHRINKAGE CRACKS:
When the evaporation rate of water mixed in
the concrete is
greater than the bleed water of concrete,
plastic shrinkage
cracks are developed on the surface of the
concrete. Basically,
this type of cracks occurs in very hot climate.
F) DUSTING:
Dusting can be prevented by taking following
precautions.
1. Maintain a suitable water/cement ratio in
the concrete.
2. Utilize dust free aggregates in the mix.
3. Guarantee appropriate hydration of
concrete.
4. Avoid early surface finishing of concret