Concrete Plant Operations
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Transcript of Concrete Plant Operations
8/3/2019 Concrete Plant Operations
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CE552 Concrete Plant Operations 1
Concrete Plant Operations
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CE552 Concrete Plant Operations 2
Purpose of Concrete Plants
• To produce a concrete mixture that:
– is cost effective
– contains the desired proportions of concrete aggregate, andadmixtures
– meets all specifications
– is consistent
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Common Plant Operations
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Materials
• Water
• Cement
• Aggregates
–
Coarse – Fine
– Recycled- slag, fly ash
• Admixtures
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Cement
• Production – http://www.cement.org/basics/images/flashtour.html
• Delivery –
Rail – Truck
– conveyor
• Storage – silos
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Stockpiling
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Aggregate Bins and Feeds
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Liquid Admixtures
• Storage
• Dosing
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Batching Operations
• Batch Materials
– Charge order- water, aea/wr, aggregates, cement, water
• Agitation- avoid headpack, cement balls
•
Truck Cleanliness – Wash off- after loading
– Wash down- at site or end of discharge
– Wash out- end of day
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Central Mix Plant – High Volumes
– Improved QC/QA
– Reduced Wear on trucks
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Batch Control
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Transit or Shrink
Mix Plant• Truck mix separately
mixes all ingredients intruck
• Shrink Mix partiallymixes in plant
• Small batch production
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Mobile Mixing Plant
• Intermittent or smallproduction quantities
• Advantages: Combinedmaterials transporter andbatching and mixingsystem. One-manoperation.
• Good preventivemaintenance program.
•
Materials must beidentical to those inoriginal mix design.
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Transportation- Agitating Trucks
• Front Discharge • Rear Discharge
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Non-agitating Trucks
• Transport concrete onshort hauls over smoothroadways.
• Cost of nonagitatingequipment is lower thanthat of truck agitators ormixers.
• Slump should be limited.
Possibility of segregation.Height upon discharge isneeded.
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Transportation- Non-Agitating Trucks
• End Dump • Belly Dump
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Unloading/Discharge
• Direct Discharge
• Pumping Operations
• Crane/Bucket Delivery
• Conveyor
– Truck mount
– Belt
• Buggy
• Armstrong Method
•
Concerns – Adding Water
– Minimize segregation
– Minimize contamination
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Adding Water
• ASTM C 94 (AASHTO M 157)- Remixing of PCC
• 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 notexceeded
– Concrete is remixed
• min. 30 rev. at mixing speed
•until uniformity is within limits
• If workability is a concern, consider a water reducing orsuper plasticizing admixture instead of water.
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Direct Discharge
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Pumping Operations
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Pump Discharge
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Crane/Bucket Delivery
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Truck Mount Conveyor
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Belt Conveyor
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Buggy and Armstrong Method
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Environmental Concerns
• Water Runoff
– washout areas at jobsites
– plant operations
• Dust Control
–
dust collection – plant washing
– truck washing
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Recycling Operations
• Returned Loads
– coarse aggregate
– fine Aggregate
– slurry
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Recycling Flow Diagram