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ABCs of Concrete Presented by Chuck Curry
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ABCs of Concrete What is concrete? Where does it come from?
How is it used? Is it all the same?.
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Early History Ancient Egyptians Mix mud & straw to make bricks
3 Early History Ancient Egyptians Mix mud & straw to make bricks Discover lime & gypsum make better binders…
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Early History Great Pyramids 3,000 BC
4 Early History Great Pyramids 3,000 BC Held title of tallest man-made structure for 3,800 years!
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Early History Ancient Chinese Mix water, rice and lime
5 Early History Ancient Chinese Mix water, rice and lime Use mortar to bind bricks…
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Early History Great Wall of China 3,000 BC 13,000 miles 6
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Improving Practices Roman Empire Pozzolans discovered
7 Improving Practices Roman Empire Pozzolans discovered Extensive use of hydraulic lime
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Improving Methods The Pantheon Largest Unreinforced Concrete Dome. 8
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Setbacks Knowledge lost with fall of Rome 400 AD
9 Setbacks Knowledge lost with fall of Rome 400 AD Not “discovered” again for 1200 years!
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The Renaissance Renaissance Period Scientific method Manufacturing
Engineering Importance of recipes
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Importance of Recipes Mix Designs Consistency Repeatability
Increased Confidence in Performance
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Industrial Methods “But if the Sand be not very sharp, then you may put a greater quantity of Sand, for Morter which hath its due proportion of Sand, is stronger than that which hath less Sand in it, altho' some think otherwise.” - Joseph Moxon, 1678
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Industrial Era Refinement of cement Consciousness of aggregates
Scientific method Engineering Efficiency
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Industrial Methods Specialization Knowledge of intended use
Mixes specific to use Cost of mixes
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Modern Era Principle components Primary applications Range of use
What and when?
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Key Benefits Widely Available Economical Continued strength gain
Rock and sand is everywhere! Economical Rock and sand generally cheap! Continued strength gain Self-healing properties Relatively easy to make
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How to Make Concrete? Rock (Coarse Aggregates) Sand (Fine Aggregates)
Water Cement Add Admixtures, when needed Mix sounds simple enough…
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How To Make a Car: Make a Body Add 4 Wheels Install Engine Paint
sounds simple enough…
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All The Same Right?
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Concrete is not Concrete!
Proportions of materials Ratio of water to cement Types of aggregates Types of admixtures All have an effect!
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Effects of… More rock versus more sand Cement quantity and w/c ratio
Smooth versus angular Types of fly ash Types of admixtures
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Types of Concrete Wet cast Dry Cast Flowable Self-Compacting
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Wet Cast Slump Concrete Old Days: Today: Achieved with high w/c ratios
Often achieved with lower w/c ratios and Water reducing admixtures
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Wet Cast
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Wet Cast Properties Pros Cons Portable More Dense Lower Permeability
Lower Absorption Nicer Finish Longer Curing Time Slower Form Cycle Delayed QC Formwork Manpower
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Wet Cast – Common Uses Slumps ‘generally’ 1-9” slump
Major Infrastructure – Dams, Highways Buildings – Columns, footings, beams Architectural – Panels, facades Cast-in-place - Curbs, inlets, manholes Transport – Roads, sidewalks, sleepers Drainage – Pipe, box culverts, etc. Residential – Drives, patios, etc.
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Dry Cast Zero Slump Concrete Cast and Strip – Mass Production!
Lower w/cm ratio
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Dry Cast Old Days: Today: Tamping – Too slow. Obsolete.
Vibrational Compaction Vibromac Packerhead Centrifugal
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Dry Cast Vibrational Compaction Packerhead Vibromac Centrifugal
Denser, faster, surface issues Packerhead Less dense, fastest, aesthetic, weaker Vibromac Part vibration and packing pressure Centrifugal Most dense*, slower, high maintenance * (of modern methods)
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Picture of dry cast slump cone?
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Dry Cast Properties Pros Cons Shorter Curing Time Rapid Form Cycle
Earlier Shipping Automated Mass Production! Less Dense Less Aesthetic More Energy Req’d Duplication of Errors
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Dry Cast – Common Uses Concrete Block Pavers
Storm and Sanitary Drainage Concrete Pipe Concrete Box Culverts Manholes
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Flowable High Fly Ash Content Not Structural
Typically used as backfill Voids in trenches Abandoned pipelines Little to no vibration
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Self-Compacting Concrete (SCC)
Spread not Slump Cement/Admix suspends aggregate Fills the container
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SCC Properties Pros Cons No vibration Complex structures Fewer voids
Less energy Less time Less manpower Complex structures Fewer voids High admix (cost) Critical proportions Interaction of admixes
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SCC – Common Uses Manholes & Inlets Utility Vaults BMPs Rehabilitation
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Chemical Admixtures Water Reducers Reduce Water Content by 5-10%
Increase Strength Decrease Porosity Increases Workability Improves Finish
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Chemical Admixtures High Range Water Reducers
Reduce Water Content > 10% Significant early and final strengths Increased flow without segregation (rheoplasticity) Helpful where vibration inhibited
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Chemical Admixtures Air Entrainment Increases air content
Evenly distributed Increases Durability, esp. to freeze/thaw cycles Reduces Strength
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Chemical Admixtures Retarders Increase set time
Good for long pours in hot weather Extended transport
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Chemical Admixtures Accelerators Decrease set time
Increase early strength Used in cold weather
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Chemical Admixtures Corrosion Inhibitors
Inhibit attacks on reinforcing steel Marine environments Heavy salt use (northern roads)
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Chemical Admixtures Ensure Proper Dosage Possible Mix Time Changes
Negative Synergies How do different admixes interact? Do you want to find out the hard way?
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Methods of Mixing Many available. Important to remember goal of mixing: Homogenous mixtures Uniform batches Tolerances – Recipes
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Paddle mixer If you are going to use a lab mixer for trial batching, you would probably use this type of mixer.
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Spiral blade or ribbon mixer
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Twin Shaft
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Turbine pan mixer
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What Concrete Would Be Best?
Manhole Riser Low Leakage Limit Exposed to Freeze/Thaw Wet Cast with Entrained Air
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What Concrete Would Be Best?
Bridge Beams High Cementitious Contents Multiple Steel Layers SCC
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What Concrete Would Be Best?
Storm Drain Pipe Mass Production Dry Cast
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Recap Value of Concrete Types of Concrete Similarities / Differences
Range of Use / Applications Importance of Recipes Effects of Admixtures Application drives Selection!
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QUESTIONS?
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