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Concrete and Concrete
Equipment
FRESH CONCRETE
To the designer, fresh concrete
is of little importance. To the
constructor, fresh concrete is
all-important, because it must
be mixed, transported, placed,
supported, consolidated,
finished, and cured.
FRESH CONCRETE
CEMENT
TRUCK
Quantities of Cement,
Aggregate and Water
Specifications may simply
define strength:
28 day strength
(i.e. 2,500, 3,000 or 6,000 psi,
25N/mm2, 30N/mm2)
MIXTURE
PROPORTIONS
• The higher the water-cement ratio, the lower
the resulting strength and durability
• The more water that is used (which is not to
be confused with the water-cement ratio), the
higher will be the slump
• The more aggregate that is used, the lower
the cost of the concrete
MIXTURE
PROPORTIONS
• The larger the maximum size of coarse
aggregate, the less the amount of
cement paste that will be needed to coat
all the particles and to provide
necessary workability.
• Adequate consolidation produces
stronger and more durable concrete.
MIXTURE
PROPORTIONS
• The use of properly entrained air
enhances almost all concrete properties
with little or no decrease in strength if the
mix proportions are adjusted for the air.
• The surface abrasion resistance of the
concrete is almost entirely a function of
the properties of the fine aggregate.
Quantities of Cement,
Aggregate and Water
Specs may define other requirements:
• Maximum size aggregate (i. e. 40mm.)
• Minimum cement content (sacks per cy
or lb/cy)
• Maximum water cement ratio by weight
or in gallons per sack of cement)
Quantities of Cement,
Aggregate and Water
• One sack of cement weighs 50kg
• One barrel of cement contains
four sacks
• Specific gravity of cement, 3.15
Quantities of Cement,
Aggregate and Water
• Specific gravity (average) of course
or fine aggregate, 2.65
• Water weighs 62.4 lb/cf
• One cf of water = 7.48 U.S. gal
• One gallon of water weighs 8.33 lb
Quantities of Cement,
Aggregate and Water
Usually the proportion of fine
aggregate varies between 25 and 45%
of total aggregate volume.
Absolute volume of any ingredient in
cubic feet equals:
Wt of the ingredient lb
Specific gravity ingredient lb cf
( )
. / 62 4
QUANITY EXAMPLE
•Max. size aggregate 1½ in.
•Min. cement content 6.0 sacks/cy
•Max. water/cement ratio 0.65
QUANITY EXAMPLE
Cement/cubic yard 6.0 sacks
6 sacks 94 lb/sack = 564 lb
Absolute volume of cement
564
3 15 62 42 87
lbcf
. ..
QUANITY EXAMPLE
Water/cubic yard
564 lb 0.65 = 366.6 lb
Absolute volume of water
366 6
1 0 62 45 88
.
. ..
lbcf
QUANITY EXAMPLE
Absolute volume of 1 cy of
concrete = 27.0 cf
Assume 6% air voids
27 0 0 06 1 62. . . cf
QUANITY EXAMPLE
Absolute volume of aggregate
=16.63 cf
27 0 2 87 5 88 1 62. . . .
QUANITY EXAMPLE
Absolute volume of sand
Assume fine aggregate 35%
Weight fine aggregate
= 962.4 lb/cy
0 35 16 63 5 82. . . cf
5 82 2 65 62 4. . .cf
QUANITY EXAMPLE
Absolute volume of coarse
aggregate
Weight course aggregate
= 1,787.5 lb/cy
16 63 5 82 10 81. . . cf
10 81 2 65 62 4. . .cf
QUANITY EXAMPLE
Assume a 700 cy placement.
Cement required
197.4 tn
564 0 700 394 800. #/ ,cy cy lb
QUANITY EXAMPLE
Assume a 700 cy placement.
Water required
30,807 gallons
366 6 700 256 620. #/ ,cy cy lb
256 620
8 33
,
. #/
lb
gal
QUANITY EXAMPLE
Assume a 6 hours for the
placement.
Or 86 gallons/minute
30 807
65 134
,, /
gal
hoursgal hr
QUANITY EXAMPLE
Assume a 700 cy placement.
Sand required
337 tn
962 4 700 673 680. #/ ,cy cy lb
QUANITY EXAMPLE
Assume a 700 cy placement.
Course aggregate required
626 tn
1 787 5 700 1 251 250, . #/ , ,cy cy lb
QUANITY
EXAMPLE
Assume a 700 cy placement.
How much for waste??
MIXING
TECHNIQUES
Transit-mixed
BATCH PLANT
Accurately proportions
aggregate and cement.
Water is measured in
the truck mixer.
CENTRAL-MIXED
Mixer
CONCRETE PLANT
STANDARDS
Cement of cementitious
materials shall be batched by
weight.
Aggregates shall be batched
by weight.
Water shall be batched by
weight or volume.
MIXER TYPES
Freefall mixers
• Tilting mixers
• Reversible mixers
Power mixers
• Pan mixers
• Trough mixers
MIXER
TYPES
Tilting
mixer
(drum) in
a central-
mix plant
MIXER TYPES
Reversible concrete mixer with a skip
and tilting hopper.
MIXER TYPES
Large
pan
mixer
MIXER
TYPES
Large
pan
mixer
MIXER TYPES
Single-
shaft
trough
mixer
MIXER TYPES
Twin-shaft
trough
mixer
HAULING CONCRETE
Transit-mix truck (truck mixer)
Maximum duration 1 ½ hr or
300 drum revolutions from
introduction of water until
placement.
TRUCK MIXER
Rear-discharge mixer
TRUCK MIXER
Front-discharge mixer
TRUCK MIXER
Trailer truck mixer
MIXER DRUM
MIXER DRUM
HAULING CONCRETE
Wet Central Mix Concrete
Using dump or agitator
trucks, 30 minute maximum
haul at 70 to 90 degrees.
CENTRAL
MIX PLANT
CENTRAL MIX PLANT
Accurately proportions
aggregate, cement and
water, and mixes these
materials automatically.
CENTRAL MIX PLANT
On-site plant for
large concrete
quantities
Compact
mobile plant
for small site
CABLE & BUCKET
SYSTEM
CABLE & BUCKET
SYSTEM
A Giant 13-cy
bucket used for
the construction
of Glenn Canyon
Dam in the 1960s
CABLE &
BUCKET
SYSTEM
CRANE &
BUCKET
SYSTEM
CRANE &
BUCKET
SYSTEM
Bucket for wall
concreting
CRANE & BUCKET
SYSTEM
CRANE & BUCKET
SYSTEM
Slab concreting
CONVEYOR SYSTEM
CONVEYOR SYSTEM
Truck-mixer-mounted
belt conveyor
Truck-Mounted
Pump
Truck-Mounted Pump
Max. horizontal reach nominal reach 12 ft
12 ft
PUMPING
Truck-Mounted Pump
PUMPING
Truck-Mounted
Pump
Consider space
allowance for
outriggers
PUMPING
Two stationary
pumps used on a
bridge project.
PUMPING
Trailer Pump PUMPING
Pump with Pipeline and
Tower-Mounted Boom
PUMPING
Pump with Pipeline
and Tower-Mounted
Boom Boom
climbing
inside core
of structure
Pump with
Pipeline and
Tower-Mounted
Boom
External tower-
mounted boom
PUMPING
Pump
with
pipeline
and tower-
mounted
boom
PUMPING
Pump with
pipeline and tower-
mounted
boom
PUMPING
Pump with
pipeline
and tower-
mounted
boom
PUMPING
Pump with
pipeline
and tower-
mounted
boom
PUMPING
Maximum theoretical outputs
of up to 300 cy per hr
Common building elements of
regular dimensions –
40 cy per hr
PUMPING OUTPUTS
Thick slabs (in excess of 20 in.)
and similar elements –
60 cy per hr
Mass concreting of large elements
(i.e. dams, raft foundations) –
80 cy per hr
PUMPING OUTPUTS
SHOTCRETING
CONCRETE
PLACEMENT
Very important to
prevent
segregation of the
coarse aggregate
during
placement.
CONSOLIDATION
Consolidation
is normally
achieved
through the
use of
mechanical
vibrators.
SCREED
TROWELING
Walk-behind
single-rotor
power trowels
TROWELING
Ride-on
double-rotor
power trowel
TEMPERATURE
When the temperature of
fresh concrete exceeds 85
or 90°F, the resulting
strength and durability of
the concrete can be
reduced.
TEMPERATURE
Most specifications require
that concrete be placed at a
temperature of less than
90°F. In hot weather it may
be necessary to cool the
ingredients before mixing
CURING
Do not forget
about the curing
requirements.
SLIPFORM PAVER
SLIPFORM PAVER
PAVING OVER DOWELS
PAVING OVER REBAR
SIDE FEEDER
Side feeder when paving over
dowels or rebar.
PAVING THE
MIDDLE LANE
CONCRETE
SMOOTHNESS
Specifications require smoothness.
A “Profileometer.” is used to measure
smoothness.
SMOOTHNESS
Monitor supply of concrete.
Mix design is but a prerequisite.
Many of the problems occurring
in pavements concern what is
done with the mix.
Control
density.
Vibration is a
vital part of the
paving process.
SMOOTHNESS
Paver Vibrators
SMOOTHNESS
Weight & Traction
The principle which makes a
slipform paver work is the
consolidation of the concrete
in a confined space.
SMOOTHNESS
Paver attitude.
The paver attitude is
the attack angle in
relation to the concrete.
SAWING
JOINTS
SAWING JOINTS
Saw depth
Resulting
crack
BRIDGE DECK
LABOR
• Carpenters
• Labors
• Cement masons
• Ironworkers
• Teamsters
• Operating engineers
SAFETY
Placing of concrete,
placing by pumping
requires particular
caution!
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