Exposed reinforcement in Aluminium shuttering
Reinforcement that
is visible on the concrete surface of any reinforce concrete is termed as exposed
reinforcement, it is one of the common types of defect that needs to be
repaired immediately after de-shuttering work is completed.
For any concrete
repair work sufficient prop supports should be used as per the instruction of
engineer in charge, especially if the repair work is to be carried out in
structural columns, walls or beams. In case of slabs if the affected area is
less, then prop is not required.
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| Exposed reinforcements |
Causes of exposed reinforcement:
Many factors
contribute for exposed reinforcement in RCC structure including poor
workmanship & quality control, however, some points are listed below
·
Most
common reason for these defects is due to improper / un-sufficient cover block
for any particular segment. Although in some instances it has been noticed that
after proper placing of cover blocks, during fixing of shuttering (Aluminium
shuttering) some cover block gets damaged, reoriented and even fall off.
·
Another
type of exposed reinforcement occurs when the concrete has aged and
deterioration of concrete leads to this defect. In this case, the chance is
very high that the reinforcement is highly corroded & replacement of
reinforcement is only applicable remedial measure.
·
Permeability
(passing ability of water through it) of concrete is also an important factor
contributing to rusting of steel & eventually leading to exposed &
highly corroded steel.
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| Exposed Reinforcement |
Repairing of exposed reinforcement:
- Chipping to be carried out on
extension portion of the exposed reinforcement identify the area of defect till
sound concrete & steel is found. Chipping is also required to make space
for the reinforcement to be pushed back. If the reinforcement is highly
corroded then the steel is to be replaced by new steel with required Ld
(Development length).
- All loose concrete shall be removed,
and exposed steel & concrete is to be cleaned using steel wire brush and
water so that no loose debris are present. Using water before the application
of chemicals also helps to achieve SSD condition which helps in the bonding of
the chemicals.
- Hammering might be required to push
back the reinforcements so that it gets the required cover.
- It the steel is not highly corroded
then corrosion resistant chemical compounds such as Sika Rustop shall be
applied on the reinforcement surface to prevent it from further rusting. If
replacement steel is required then use of chemical is not compulsory, however
providing Ld or welding is required to maintain the continuity of
the steel.
- Before sealing the void with fresh
concrete, bonding agents such as Fosroc Nitobond EP to be used for better
bonding of new & old / existing concrete.
- Application of micro-concrete such as
Sika Microcrete 4 or cement based grouting compound such as Sika 122 Top HS can
be used to fill up the chipped-out area depending upon the structural important
of that particular RCC member. After which finish to be made with a trowel.
- Curing is compulsory as per the
technical data sheet of the micro concrete used or as per the instruction of
engineer in charge. However, it is always a good practice to cure it for at
least 7 days.
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