VACUUM DEWATERED
FLOORING (VDF) - METHODOLOGY
A. PREPARATION
OF SUB-GRADE
Ø Sub-grade should be laid according
to specifications, levels as recommended by the consultant
Ø Ensure that proper consolidation of
the sub-grade has been achieved before proceeding for the PCC bed
Ø Provide and lay PCC bed above the
sub-grade as per thickness mentioned in the drawing
Ø Provide a reinforcement mesh as per
specification and the drawings
Ø Clean the entire PCC bed with water
before concreting
B. DEWATERING
AND FINISHING
Ø Concreting should be carried out
with concrete of right grade and slump. (See: Concreting)
Ø Concrete intermediate/ alternate
panels shuttered by ISMC runners or continuous bull marks.
Ø Ensure proper expansion joints as
per working drawings and protected
Ø Dewatering mat to be used to remove
excess water from the concrete surface to ensure concrete of the highest
strength is achieved.
Ø The dewatering mat should be
properly laid to prevent air leakage. Care should be taken in ensuring that
excess water does not enter the dewatered area.
Ø After initial set of concrete (2-3
hours), the top surface of concrete is finished using a power trowel. Care
should be taken that no impact load is transferred to the finished surface.
Ø No load or stepping on concrete
should be avoided, before initial set of finished concrete.
Ø Heavy vibrations should be avoided
in vicinity of the VDF area.
C. TESTING
OF CONCRETE
SLUMP TEST
Ø Conduct slump cone test, one during
the start, one at midday and one towards the close of days work.
Ø Any load under suspicion can be
checked for slump on case-to-case basis.
CUBE TEST
Ø The sample is made at point of
discharge of mixture.
Ø Take 3 samples after 7 days and 3
samples after 28 days strength.
Ø Every 100 cum or 10 batches of
concrete (whichever is smaller) should be represented by a sample of test
cubes.
Ø For concrete manufactured at site,
there must be representative samples for the day’s work and for different
elements like footing, slab, column and wall.
Ø Test results should be discussed
with the project in-charge even if the results are satisfactory
Ø In case of cube failure, the element
to be identified and non-destructive test to be conducted.
TOOLS TO BE USED BY TRADESMEN
Required tools must be available at site to ensure correct
work. Basic tools of the concreting gang are:
1. Vacuum
Dewatering machine
2. Power
Trowels
3. Trowels
4. Gum boots
5. Dumpy
levels
6. Spirit
levels 1-3m
7. Measuring
tape
8. Screed
finishing darby
9. Steel
trash tracks
10. Hammer
11. Leveling
trowels
12. Wheelbarrow
13. Long handle
Aluminium leveler with spirit level
14. Masons
brushes and buckets
15. High
pressure water cleaners
INSPECTION METHODOLOGY FOR QUALITY ASSURANCE
1. Personnel
v Ensure all personnel are wearing
gumboots
2. Before
Concreting
v Ensure shuttering is sealed with
sealing tape so as there is no leakage of slurry
v All reinforcements are in place
especially chairs
v All cover blocks damaged during
reinforcement layout are replaced
3. During Concreting
v Ensure proper grade of concrete as
recommended by the consultant is employed
v Ensure proper expansion joints as
per working drawings and protected
v Check the top surface of fresh
concrete for eveness of top surface
4. After Concreting
v Top surface is checked for
straightness using Aluminium straight edge or leveling thread as the case may
be.
v Curing carried as per
guidelines
v Water level is maintained during
ponding
v Ensure the cube test results are
available at the end of the term indicated
TOOLS TO BE USED FOR QUALITY INSPECTION
1. Dumpy
levels to check finished slab level
2. Aluminium
straight edge
3. Leveling
thread
4. Spirit
levels 1-3m
5. Measuring
tape
6. All the
relevant related drawings
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