Transcript Placing and Finishing Concrete

Placing and Finishing
Concrete
Basic Requirements for
Placing Concrete (1)
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Preserve concrete quality
Water-cement ratio
 Slump
 Air-content
 Homogeneity
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Placing and
Finishing Concrete
Avoid separation of
aggregate and mortar
Basic Requirements for
Placing Concrete (2)
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Placing and
Finishing Concrete
Avoid excessive horizontal
movement
Consolidate adequately
Maintain sufficient placement
capacity
Choose the right equipment for
the concrete
Preparation Before Placing
Includes:
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Placing and
Finishing Concrete
Trimming the subgrade
Preparation Before Placing
Includes:
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Placing and
Finishing Concrete
Moistening the subgrade
Preparation Before Placing
Includes:
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Placing and
Finishing Concrete
Compacting the subgrade
Depositing Concrete
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Placing and
Finishing Concrete
DO NOT —
(a) disturb saturated subgrades so
bearing capacity is maintained
(b) deposit on frozen subgrade
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Deposit continuously and as near as
possible to its final position
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Rate of placement should be such
that previously placed concrete has
not set when the next layer is placed
upon it
Depositing Concrete
Slab Construction
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Start placing along perimeter at one
end with each batch discharged against
previously placed concrete
Do not —
(a) dump in separate piles & then
level and work together
(b) deposit in large piles & then
move horizontally into position
These practices result in segregation
Placing and
Finishing Concrete
(mortar flows ahead of coarser material)
Depositing Concrete
Effective use of
wheelbarrows
Placing and
Finishing Concrete
Discharging into previously
placed concrete
Incorrect Placement with
Conveyor Belt
Baffle
Mortar
Mortar
Rock
Shallow
hopper
Rock
Placing and
Finishing Concrete
Mortar
Placement with Conveyor
Belt
Provide at least 0.6 m
(24 in.) headroom for
downpipe, elephant
trunk or equivalent
Placing and
Finishing Concrete
Belt Scraper
No
Separation
Depositing Concrete
Pavement Slab
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Placing and
Finishing Concrete
Concrete deposited in
front of slip form paver
by dump trucks
Concrete spread
evenly across the
subgrade by the paver
before consolidation
and finishing
Depositing Concrete
Curb/Curb and Gutter
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Placing and
Finishing Concrete
Concrete deposited
into hopper of slip
form curb and gutter
machine which then
extrudes the concrete
into the desired
shape
Depositing Concrete
Walls
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Deposit in horizontal layers of
uniform thickness
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Placing and
Finishing Concrete
Reinforced — 150 mm to 500 mm
Mass — 375 mm to 500 mm
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Consolidate each layer before
next is placed
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Timely placement & consolidation
prevents flow lines and cold joints
Horizontal Construction Joint
Placing and
Finishing Concrete
Horizontal Construction Joints
Placing and
Finishing Concrete
Underwater Placement
Methods
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Placing and
Finishing Concrete
Tremie
Pump
Bottom dump buckets
Grouted preplaced
aggregate (specialized)
Toggle bags
Bagwork
Diving bell
Placing Concrete
Under Water
Basic Recommendations
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Placing and
Finishing Concrete
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 Concrete
Underwater
Placing and
Finishing Concrete
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Used: Tremie
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Advantages: Can be used to
funnel concrete down through
the water into the structure.
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Watch for: Discharge end
always has to be buried in fresh
concrete to ensure seal
between water and concrete
mass.
Consolidating
Concrete
Placing and
Finishing Concrete
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Internal Vibration
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External Vibration
Internal Vibration
Vibrator
d
1½ R
Placing and
Finishing Concrete
Radius of Action
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)
20-40
(3/4-1½)
9000-15,000
80-150
(3-6)
0.8-4
(1-5)
30-60
(1¼-2½)
8500-12,500
130-250
(5-10)
2.3-8
(3-10)
50-90
(2-3½)
8000-12,000
180-360
(7-14)
4.6-15
(6-20)
Placing and
Finishing Concrete
Application
Plastic and flowing
concrete in thin
members. Also used
for lab test
specimens.
Plastic concrete in
thin walls, columns,
beams, precast piles,
thin slabs, and along
construction joints.
Stiff plastic concrete
(less than 80-mm [3in.] slump) in general
construction .
Adapted from ACI 309
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
Placing and
Finishing Concrete
Haphazard random penetration of the
vibrator at all angles and spacings
without sufficient depth will not assure
intimate combination of the two layers
Placing Concrete in a
Sloping Lift
CORRECT
Start placing at bottom of slope so
that compaction is increased by
weight of newly added concrete.
Vibration consolidates the concrete.
INCORRECT
Placing and
Finishing Concrete
When placing is begun at top of slope
the upper concrete tends to pull
apart especially when vibrated below
as this starts flow and removes from
concrete above.
External Vibration
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Form vibrators
Vibrating tables
Surface vibrators
Vibratory screeds
 Plate vibrators
 Vibratory roller screeds
 Vibratory hand floats or
trowels
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Placing and
Finishing Concrete
Consolidating Concrete
Inadequate consolidation
can result in:
Honeycomb
 Excessive amount of entrapped
air voids (bugholes)
 Sand streaks
 Cold joints
 Placement lines
 Subsidence cracking
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Placing and
Finishing Concrete
Nuclear Gauges to Determine
Subbase Compaction
Placing and
Finishing Concrete
Screeding (Strikeoff)
The process of cutting off excess
concrete to bring the top surface of a
slab to proper grade
Placing and
Finishing Concrete
Vibratory
Screeds
Placing and
Finishing Concrete
Bullfloating
Placing and
Finishing Concrete
Darbying
Placing and
Finishing Concrete
Edging
Edging densifies and compacts concrete
next to forms where floating is less effective
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Placing and
Finishing Concrete
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
Highway Straightedges
Placing and
Finishing Concrete
Floating (Power or Hand)
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Placing and
Finishing Concrete
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.
Troweling
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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.
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Placing and
Finishing Concrete
Brooming
Placing and
Finishing Concrete
Tining
Placing and
Finishing Concrete
Curing and Protection
Placing and
Finishing Concrete
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Cure for 7 days
Placing on Hardened Concrete
Preparing Hardened Concrete
Placing and
Finishing Concrete
Bonding New to Previously
Hardened Concrete
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Placing and
Finishing Concrete
Cement-sand
grout
Latex
Epoxy
Isolation Joints
Placing and
Finishing Concrete
Contraction Joints
Placing and
Finishing Concrete
Spacing of Contraction
Joints in Meters
Slab
thickness,
mm
100
125
150
175
200
225
250
Placing and
Finishing Concrete
Maximum-size
aggregate
less than 19 mm
2.4
3.0
3.75
4.25
5.0
5.5
6.0
Maximum-size
aggregate
19 mm and larger
3.0
3.75
4.5
5.25
6.0
6.75
7.5
Metric
Spacing of Contraction
Joints in Feet
Slab
thickness, in.
4
5
6
7
8
9
10
Placing and
Finishing Concrete
Maximum-size
aggregate
less than ¾ in.
8
10
Maximum-size
aggregate
¾ in. and larger
10
13
12
14
16
15
18
20
18
20
23
25
Inch-Pound
Making Contraction Joints
Grooving tool
on bull-float
Placing and
Finishing Concrete
Dry-cut sawing concrete
Construction
Joints
Placing and
Finishing Concrete
Joint Layout for Slabs
Basic Factors to Remember
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Placing and
Finishing Concrete
Panels created by contraction
joints should be approximately
square
Panel aspect ratio max. 1½ to 1
Contraction (control) joints should
only terminate at a free edge or at
an isolation joint
When joint spacing exceeds 4.5 m
(15 ft), load transfer by aggregate
interlock decreases significantly
Typical Joint Layout
Placing and
Finishing Concrete
Finishing Operations
Single Course Floors
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Consolidation
Strike-off
Edging
Darbying or Bull Floating
Lapse of Time
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Edging
Grooving (if desired)
Floating (power or hand)
Troweling (power or hand)
Lapse of Time
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Placing and
Finishing Concrete
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Second Troweling (power or hand)
Final Troweling (hand)
Curing
Finishing Operations - Exterior Slabs
Sidewalks, Driveways etc.
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Consolidation
Strike-off
Depress aggregate with metal/wood strip
at joint location if hand tooled
Darbying or Bull floating
Lapse of time
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Edging
Jointing (optional if hand tooled)
Floating
Lapse of time
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Placing and
Finishing Concrete
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Texturing (brooming/swirl float finish)
Curing
Patching
Placing and
Finishing Concrete
Curing Patches
Placing and
Finishing Concrete
Cleaning Concrete
Surfaces
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Placing and
Finishing Concrete
Cleaning methods:
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Water
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Chemical
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Mechanical
Finishing Formed
Surfaces
Placing and
Finishing Concrete
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Rough-form finishes
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Smooth off-the-form finish
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Smooth, rubbed finish
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Sand-floated finish
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Grout cleandown
(sack-rubbed finish)
Special Surface Finishes
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Pattern and Textures
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Exposed Aggregate Concrete
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Colored Finishes
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Stains, Paints and Clear
Coatings
Placing and
Finishing Concrete
Placing and
Finishing Concrete
Working Safely with Concrete
Protect:
Placing and
Finishing Concrete
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Your Eyes
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Your Back
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Your Skin
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.
Placing and
Finishing Concrete
http://www.cement.org/pdf_files/ms271.pdf
Videos 1/4
Placing and Consolidating
Placing and
Finishing Concrete
Vibration
Videos 2/4
Finishing I
Placing and
Finishing Concrete
Finishing II
Videos 3/4
Contraction Joints
Placing and
Finishing Concrete
Jointing
Videos 4/4
Improper Finishing
Placing and
Finishing Concrete