What is Rebarring?
Fixing of new reinforcement steel to existing concrete
structure with drilling in concrete 150mm or 10 times of Diameter whichever in
maximum to 600mm deep as per depend on structural design with applying chemical
to bar with testing as per the design standards requirement.
Why need to rebar?
When some changes in
design of structures or failure of the existing structure or existing steel reinforcement
is found low in quality or cut or break of any bar in existing structure all
those locations need to rebar as per standard norms are given by structural
consultant or RCC designer.
Where & Why we can rebar?
We can rebar
the steel reinforcement at the following locations.
Rebarring
for Footing and Column: For Column Jacketing.
Rebarring
for Beam: For Chajja/Projection.
Rebarring
for Beam: New beam structure introduced by RCC designer.
Rebarring at
Slab: Extension of Slab.
Rebarring in
Column: Fixing of Lintel at door and windows and
Rebarring at
Column, Beam, Slab, Lift Wall, Retaining Wall, etc: if any bar cut/break due to
by mistake.
What is
Current Practice of Rebarring?
Currently
all the contractor, developers, and some engineers are doing wrong practice for
doing rebarring because they are always doing rebarring at various location any
levels due to forgotten to keep dowels, or keep wrong diameter steel dowels,
etc. but all the time everyone is following the wrong practice to close his
mistakes in concrete. Because no one can find any mistakes after concreting. And
some contractors are using this practice normally with mutual understanding and
discussion with the site engineer or project manager.
Some builders, developers,
contractors and engineers also don’t know the standard practice of Rebarring.
But due to avoid the hurdles of breaking of the existing structure, and re-reinforcement
of this structure, they are always thinking to save the cost of material,
labour, and to save time. Some contractors are giving this benefit behind
at builder, developer, project manager, etc.
This is the current process of rebarring which is using at everyone was.
1. Drilling
in the existing structure. :
Sometimes the bore depth is not up to 10 times the diameter of the bar or 150mm, because there will be
some obstructions of steel bars of existing steel in the existing structure. Also not
proper care is taken when drilling like the diameter of the bar. Depth of drill, perpendicular
to the existing structure to keep dowels in line. Spacing is not maintained
properly due to obstructions of existing steel bars. Contractors are always
using a small drill machine that is needed to use by a single hand and needs to
operate manually. But due to that drills and the bore is not perpendicular to the existing structure.
2. Cleaning
of Drills/bore:
No one is
clean the bore properly and remove all the dust particles where can put the
bar. Also, no one is using blower on any other tools to clean the drill or
bore.
3. Fixing of Bar:
Some
contractors are directly fixing the bar in the drill without using any chemicals. Some contractors
are using GP2 cement to show the engineer and project manager. Also some
contractors are using any diameter of bar as well as rusted, dirty, oily bars
are used to rebarring without discussing with a technical person.
4. Immediate
shuttering and concreting:
Contractors
are always want to close the mistakes of steel reinforcements, shuttering,
sizes, etc. at this time contractor is immediate complete rebarring, same day
shuttering will fix and concrete work also complete, but no one can cross-check
the quality of rebarring an all after concreting.
5. No rebarring
test
When work is
completed with the above procedure, no one can check the pull-out test of the bar.
What is
Standard Rebarring Procedure?
Before Rebarring
always keep one sentence in mind “Rebarring is 2nd option to
rectify the Mistakes from someone like a structural designer, contractor,
engineer, architect, or permission
changed, government rules changed, etc. to avoid losses of material, labour and
time.”
Following
are the steps to show the standard procedure of rebarring.
1. Check the
Drawing.
Check the
drawing and compare the existing drawing and changed drawing, with the help of
drawing we can easily cross-check the exact location of the drawing.
2. discuss
with the project manager and RCC designer or structural consultant.
You need to
discuss the details of the situation with RCC designer or structural consultant
and project manager to given the decision on this situation. You can arrange
the site visit of the structural consultant to understand the site condition.
3. rebarring
drawings from a consultant.
After the written direction given by a structural consultant or RCC designer, request to
issue the revise drawing with rebarring details. They can give you all the
details about the rebarring of steel as per load calculations as well as they will
give you the diameter of the bar, the diameter of the drill, depth of bore. Which chemical should be used, what type of tests needs to do, etc.
4. Drilling
of Bore:
Drilling of
Bore from the standard agency which is certified by rebarring chemical manufacturers
like Hilti, Fischer, Wurth, Fosroc, etc. those standards companies are giving
you pull out tests at your site, with a quality report. Drilling should be 10
times dia. Or as per given by the structural designer.
5. Cleaning
of bore:
When the drilling process is complete, there may be a lot of dust balance in the bore
which is need to remove properly, for cleaning of bore you can use water
pressure, or air blower. But all dust should be removed from the bore.
6. Application of Chemical:
Drilling the agency is certified from the standard chemicals, those agencies are expert in rebarring
and application of rebarring chemicals. They are using chemical guns to fill
full of chemicals in the bore as per the standard procedure. Generally, 60% to 75% of the bore will be fill by the chemical.
7. Fixing of
Bar:
This agency
will fix & press the cleaned and rust-free bar in this bore which is filled
by the chemical. At the time of fixing and pressing the bar in bore some chemicals
will come out near the bar, but don’t worry this is standard practice. After rebarring
work complete wait for 4 to 5 hours to gain the strength. Some chemical
companies are giving 30min time to set the chemical but you should wait for 3 to 4
hours to further process.
After rebarring
work completed wait for 48 to 72 hours to pull out tests.
What is pull out a test of rebarring? We can check in the next blog.
Team
CBEC India
