batching, mixing, transporting, and handling concrete
TRANSCRIPT
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Batching, Mixing, Transporting, and
Handling Concrete
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Batching, Mixing, Transporting, and Handling Concrete
Ordering Ready Mixed Concrete
Specify: Coarse aggregate size Slump Air content Basis for proportioning,
select Options A ,B, or C.
ASTM C 94ASTM C 94
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Batching, Mixing, Transporting, and Handling Concrete
Ordering Ready Mixed Concrete
Option A—performance based:
Purchaser specifies: Compressive strength
Concrete producer selects mix proportions.
ASTM C 94ASTM C 94
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Batching, Mixing, Transporting, and Handling Concrete
Ordering Ready Mixed Concrete
Option B—prescription based:
Purchaser specifies mixture proportions including:
Cement content Water content Admixture type and content
ASTM C 94ASTM C 94
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Batching, Mixing, Transporting, and Handling Concrete
Ordering Ready Mixed Concrete
Option C—mixed option:
Purchaser specifies: Compressive strength Cement content Admixture type and content
Concrete producer selects mix proportions.
ASTM C 94ASTM C 94
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Batching, Mixing, Transporting, and Handling Concrete
Batching
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Batching, Mixing, Transporting, and Handling Concrete
Stationary Mixing
Stationary Mixers Onsite or Central Mix R/M plant Used for complete or shrink
mixing Mixer Types ― up to 9m3
Tilting or non-tilting drum Open top revolving blade or
paddle Typical complete mixing times
Minimum of 1 min. for up to 1 yd3 or less mixer capacity plus 15 sec. for each additional yd3 or fraction thereof
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Batching, Mixing, Transporting, and Handling Concrete
Ready Mixed Concrete
Shrink-mixed concrete mixed partially in a
stationary mixer and completed in a truck mixer
Truck-mixed concrete mixed completely in a
truck mixer
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Batching, Mixing, Transporting, and Handling Concrete
Ready Mixed Concrete
Central-mixed concrete mixed completely in a
stationary mixer delivered in
a truck agitator a truck mixer operating
at agitating speed a nonagitating truck
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Batching, Mixing, Transporting, and Handling Concrete
Ready Mix Plant
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Batching, Mixing, Transporting, and Handling Concrete
Truck Mixed Concrete
70 to 100 revolutions required for mixing,
mixing speed = 6 to 18 rpm
After mixing, drum revolves at agitating speed, 2 to 6 rpm
Discharge before exceeding 300 drum revolutions
Discharge before 1½ hours
ASTM C 94ASTM C 94
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Batching, Mixing, Transporting, and Handling Concrete
Mobile Batcher Mixer
Used for: Intermittent production of concrete at jobsite, or small quantities.
Advantages: Combined materials transporter and batching and mixing system. One-man operation.
Watch for: Good preventive maintenance program. Materials must be identical to those in original mix design.
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Batching, Mixing, Transporting, and Handling Concrete
Nonagitating Truck
Used for: Transport concrete on short hauls over smooth roadways.
Advantages: Cost of nonagitating equipment is lower than that of truck agitators or mixers.
Watch for: Slump should be limited. Possibility of segregation. Height upon discharge is needed.
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Batching, Mixing, Transporting, and Handling Concrete
Agitator Trucks
Used for: Transporting concrete for all uses. Haul distances must allow discharge of concrete within 1½ hours.
Advantages: Operate usually from central mixing plants.
Watch for: Timing of deliveries should suit job organization. Concrete crew and equipment must be ready onsite to handle concrete.
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Batching, Mixing, Transporting, and Handling Concrete
Remixing Concrete (1)
Water may be added at jobsite provided:
Spec. w/c-ratio is not exceeded Measured slump less than specified Allowable mixing and agitating time
(or drum revolutions) are not exceeded
Concrete is remixed min. 30 rev. at mixing speed until uniformity is within limits
ASTM C 94 (AASHTO ASTM C 94 (AASHTO M 157)M 157)
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Batching, Mixing, Transporting, and Handling Concrete
Transporting and Handling
Used for: Short flat hauls on all types of onsite concrete construction.
Advantages: Versatile—ideal inside and on jobsites with changing placing conditions.
Watch for: Slow and labor intensive.
Wheelbarrows and Buggies
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Batching, Mixing, Transporting, and Handling Concrete
Belt conveyor
Used for: Conveying concrete horizontally or higher/lower level.
Advantages: Adjustable reach, traveling diverter, variable speed.
Watch for: End-discharge arrangements needed to prevent segregation and mortar on return belt. Belt cover needed in hot and windy weather.
Transporting and Handling
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Batching, Mixing, Transporting, and Handling Concrete
Truck mounted conveyors
Used for: Conveying concrete horizontally or higher/lower level.
Advantages: Conveyer arrives with concrete. Adjustable reach and variable speed.
Watch for: End-discharge arrangements needed to prevent segregation and mortar on return belt. Belt cover needed in hot and windy weather.
Transporting and Handling
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Batching, Mixing, Transporting, and Handling Concrete
Buckets
Used with: Cranes, cableways, and helicopters.
Advantages: Enables full versatility of cranes, cableways, and helicopters to be exploited. Clean discharge.
Watch for: Select bucket capacity to conform to size of the concrete batch and capacity of placing equipment.
Transporting and Handling
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Batching, Mixing, Transporting, and Handling Concrete
Rear Discharge Front Discharge
Transporting and Handling
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Batching, Mixing, Transporting, and Handling Concrete
Cranes and Buckets Used for: Work above ground
level. Advantages: Can handle
concrete, reinforcing steel, formwork, and sundry items.
Watch for: Has only one hook. Careful scheduling between trades and operations is needed to keep crane busy
Transporting and Handling
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Batching, Mixing, Transporting, and Handling Concrete
Pumps
Used for: Conveying concrete from central discharge point to formwork.
Advantages: Pipelines take up little space and can be readily extended. Delivers concrete in continuous stream. Pump can move.
Watch for: Constant supply of freshly-mixed concrete is needed without any tendency to segregate.
Transporting and Handling
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Batching, Mixing, Transporting, and Handling Concrete
Flexible Hose at End of Pump’s Rigid Pipeline
Transporting and Handling
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Batching, Mixing, Transporting, and Handling Concrete
Screw Spreaders
Used for: Spreading concrete over large flat areas.
Advantages: Concrete can be quickly spread over a wide area to a uniform depth.
Watch for: They are normally used as part of a paving train. They should be used for spreading before vibration is applied.
Transporting and Handling
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Batching, Mixing, Transporting, and Handling Concrete
Work Above Ground Level
Transporting and Handling
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Batching, Mixing, Transporting, and Handling Concrete
Videos 1/3
Stationary MixersBatching
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Batching, Mixing, Transporting, and Handling Concrete
Videos 2/3
Nonagitating MixersTruck Mixer Types
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Batching, Mixing, Transporting, and Handling Concrete
Videos 3/3
Agitators