The document provides information on placing and finishing concrete. It discusses basic requirements for placing concrete including preserving concrete quality and avoiding separation. It covers preparation of the subgrade, depositing concrete, consolidating concrete through internal and external vibration, screeding, floating, troweling, finishing formed surfaces, and special finishes. It also addresses construction joints, patching, curing, cleaning, and working safely with concrete. The overall document is a guide on best practices for properly placing and finishing concrete.

1. NATIONAL INSTITUTE OF TECHNOLOGY AGARTALA
Placing and Finishing
Concrete
Presented By:- RAVI GUPTA (10UCE111)
Department Of Civil Engineering
NIT Agartala

2. Basic Requirements for
Placing Concrete (1)
 Preserve concrete
quality
◦ Water-cement ratio
◦ Slump
◦ Air-content
◦ Homogeneity
 Avoid separation of
aggregate and mortar
Placing and Finishing Concrete

3. Preparation Before Placing
Includes:
 Trimming the subgrade
Placing and Finishing Concrete

4. Preparation Before Placing
Includes:
 Moistening the subgrade
Placing and Finishing Concrete

5. Preparation Before Placing
Includes:
 Compacting the subgrade
Placing and Finishing Concrete

6. Depositing Concrete
 DO NOT —
(a) disturb saturated subgrades
so bearing capacity is
maintained
(b) deposit on frozen subgrade
 Deposit continuously and as
near as possible to its final
position
 Rate of placement should be
such that previously placed
concrete has not set when the
next layer is placed upon Concrete
Placing and Finishing
it

7. Depositing Concrete
Effective use of
wheelbarrows
Discharging into previously
placed concrete Concrete
Placing and Finishing

8. Incorrect Placement with
Conveyor Belt
Baffle
Mortar Rock Mortar
Shallow
hopper
Rock Mortar
Placing and Finishing Concrete

9. Placement with Conveyor
Belt
Provide at least 0.6 m Belt Scraper
(24 in.) headroom for
downpipe, elephant
trunk or equivalent
No
Separation
Placing and Finishing Concrete

10. Depositing Concrete
Pavement Slab
 Concrete deposited in
front of slip form
paver by dump trucks
 Concrete spread
evenly across the
subgrade by the
paver before
consolidation and
finishing
Placing and Finishing Concrete

11.  Tremie Underwater Placement
 Pump Methods
 Bottom dump buckets
 Grouted preplaced aggregate (specialized)
 Bagwork
Placing and Finishing Concrete

12. Placing Concrete
Under Water
Basic Recommendations
 Water velocity 3 m (10 ft) /
min.
 Water temperature 5°C
(if below — test for strength
gain)
 w/c 0.45
 Cementing materials content
390 kg/m3 (600
lb/yd3)
 Slump range 150 to 225 mm (6
to 10 in.) Placing and Finishing Concrete

13. Placing Concrete
Underwater
 Used: Tremie
 Advantages: Can be used to
funnel concrete down through
the water into the structure.
 Watch for: Discharge end
always has to be buried in fresh
concrete to ensure seal
between water and concrete
mass.
Placing and Finishing Concrete

14. Consolidating
Concrete
 Internal Vibration
 External Vibration
Placing and Finishing Concrete

15. Internal Vibration
Vibrator
d
1½ R
Radius of Action
Placing and Finishing Concrete

16. Internal Vibrators
Recommended Approximate Rate of
Diameter frequency, radius of placement,
of head, vibrations per action, mm m3/h
mm (in.) minute (in.) (yd3/h) Application
Plastic and flowing
20-40 80-150 0.8-4 concrete in thin
9000-15,000 members. Also used
(3/4-1½) (3-6) (1-5) for lab test
specimens.
Plastic concrete in
30-60 130-250 2.3-8 thin walls, columns,
8500-12,500 beams, precast piles,
(1¼-2½) (5-10) (3-10) thin slabs, and along
construction joints.
Stiff plastic concrete
50-90 180-360 4.6-15 (less than 80-mm [3-
8000-12,000 in.] slump) in general
(2-3½) (7-14) (6-20)
construction .
Placing and Finishing Concrete Adapted from ACI 309

17. Systematic Vibration of
Each New Lift
CORRECT
Vertical penetration a few inches into
previous lift (which should not yet be
rigid) of systematic regular intervals
will give adequate consolidation
INCORRECT
Haphazard random penetration of the
vibrator at all angles and spacings
without sufficient depth will not assure
intimate combination of the two layers
Placing and Finishing Concrete

18. Consolidating Concrete
Inadequate consolidation
can result in:
◦ Honeycomb
◦ Excessive amount of entrapped
air voids (bugholes)
◦ Sand streaks
◦ Cold joints
◦ Placement lines
◦ Subsidence cracking
Placing and Finishing Concrete

19. Nuclear Gauges to Determine
Subbase Compaction
Placing and Finishing Concrete

20. Screeding (Strikeoff)
The process of cutting off excess
concrete to bring the top surface
of a slab to proper grade
Placing and Finishing Concrete

21. Vibratory
Screeds
Placing and Finishing Concrete

22. Darbying
Placing and Finishing Concrete

23. Edging
Edging densifies and compacts concrete
next to forms where floating is less effective
 Required along all edge forms,
isolation and construction
joints
in floors and exterior slabs
 Cut concrete away from forms
to a depth of 25 mm with a
pointed mason or margin
trowel
 Edging may be required after
each subsequent finishing
operation for interior slabs
Placing and Finishing Concrete

24. Highway Straightedges
Placing and Finishing Concrete

25. Floating (Power or Hand)
 To embed aggregate
particles just beneath
the surface
 To remove slight
imperfections, humps,
and voids
 To compact the mortar
at the surface in
preparation for
additional finishing
operations.
Placing and Finishing Concrete

26. Troweling
 Creates smooth,
hard,dense surface
 Exterior concrete
should not be
troweled because:
◦ it can lead to a loss of
entrained air caused by
overworking the surface
◦ troweled surfaces can
be slippery when wet.
Placing and Finishing Concrete

27. Brooming
Placing and Finishing Concrete

28. Tining
Placing and Finishing Concrete

29. Curing and Protection
 Cure for 7 days
Placing and Finishing Concrete

30. Placing on Hardened Concrete
Preparing Hardened Concrete
Placing and Finishing Concrete

31. Bonding New to Previously
Hardened Concrete
 Cement-sand
grout
 Latex
 Epoxy
Placing and Finishing Concrete

32. Contraction Joints
Placing and Finishing Concrete

33. Spacing of Contraction
Joints in Meters
Slab Maximum-size Maximum-size
thickness, aggregate aggregate
mm less than 19 mm 19 mm and larger
100 2.4 3.0
125 3.0 3.75
150 3.75 4.5
175 4.25 5.25
200 5.0 6.0
225 5.5 6.75
250 6.0 7.5
Placing and Finishing Concrete Metric

34. Making Contraction Joints
Grooving tool
on bull-float
Dry-cut sawing concrete
Placing and Finishing Concrete

35. Construction
Joints
Placing and Finishing Concrete

36. Patching
Placing and Finishing Concrete

37. Curing Patches
Placing and Finishing Concrete

38. Cleaning Concrete
Surfaces
 Cleaning
methods:
◦ Water
◦ Chemical
◦ Mechanical
Placing and Finishing Concrete

39. Finishing Formed
Surfaces
 Rough-form finishes
 Smooth off-the-form finish
 Smooth, rubbed finish
 Sand-floated finish
 Grout cleandown
(sack-rubbed finish)
Placing and Finishing Concrete

40. Special Surface Finishes
 Pattern and Textures
 Exposed Aggregate
Concrete
 Colored Finishes
 Stains, Paints and Clear
Coatings
Placing and Finishing Concrete

41. Placing and Finishing Concrete

42. Working Safely with Concrete
Protect:
 Your Eyes
 Your Back
 Your Skin
Placing and Finishing Concrete

43. Precautions
WARNING: Contact with wet (unhardened) concrete, mortar,
cement, or cement mixtures can cause SKIN IRRITATION, SEVERE
CHEMICAL BURNS (THIRD-DEGREE), or SERIOUS EYE
DAMAGE. Frequent exposure may be associated with irritant and/or
allergic contact dermatitis. Wear water-proof gloves, a long-sleeved
shirt, full-length trousers, and proper eye protection when working
with these materials. If you have to stand in wet concrete, use
waterproof boots that are high enough to keep concrete from flowing
into them. Wash wet concrete, mortar, cement, or cement mixtures
from your skin immediately. Flush eyes with clean water immediately
after contact. In-direct contact through clothing can be as serious as
direct contact, so promptly rinse out wet concrete, mortar, cement,
or cement mixtures from clothing. Seek immediate medical attention
if you have persistent or severe discomfort.
http://www.cement.org/pdf_files/ms271.pdf
Placing and Finishing Concrete