Transcript BASIC CONCRETE PRINCIPLES - Area10FFA

BASIC CONCRETE
PRINCIPLES
ESTIMATING THE MATERIALS
NEEDED FOR CONCRETE
#8604A
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FOUR RULES FOR A
QUALITY PRODUCT
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Use proper ingredients
Correctly proportion & measure ingredients
Thoroughly mix the ingredients
Properly finish and cure the poured concrete
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ADVANTAGES OF USING
CONCRETE
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Fire proof
Durable and permanent
Watertight
Economical
Sanitary
Low maintenance
Attractive
Termite & rodent proof
Storm resistant
Can be “homemade”
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AGRICULTURAL USES
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Fence posts
Driveways
Walls & foundations
Septic tanks
Walks
Water troughs
Feeding floors
Steps
Cattle guards
etc
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COMPOSITION OF
CONCRETE
• Portland cement
• Water
• Aggregates (sand and
gravel)
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WHAT IS PORTLAND
CEMENT
• Manufactured from lime, iron oxide, silica,
and alumna.
• It is mixed in proper proportion and heated
in a kiln to approximately 3000 degrees F.
• Resulting material is called clinker
• Clinker is than pulverized and mixed with
gypsum into a fine powder.
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ORIGIN OF PORTLAND
CEMENT
• Joseph Aspdin, in the early 19th century and the
founder of the process that is still used today used
the term because the cement he produced was the
color of stone taken from the quarries on the
island of Portland off the coast of England.
• Portland cement is packaged in sacks containing 1
cubic foot which weighs 94 lbs.
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AGGREGATES
• Basic filler of sand, crushed stone, & gravel
• Sand is a fine aggregate less than ¼ inch.
• Gravel is a coarse aggregate more than ¼
inch.
• Coarse aggregate add strength.
• Aggregates are cheaper than cement and
considered a cost reducing material.
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WATER
• Should be clean and free from impurities.
• Impurities affects strength, coloration, corrosion
of reinforcement steel and wire.
• It also affect setting time
• When all ingredients are properly mixed, the
combined weight of a one cubic foot of concrete is
150-160 lbs.
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QUALITY OF CONCRETE
• Consistency or slump refers to the
“wetness” or “dryness of the mix.
• Excessive slump can be corrected by the
addition of aggregate.
• Plastic consistency is the best.
• Never exceed 6 inches of slump
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CONCRETE SLUMP RANGES
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Reinforced foundation walls –Min 2” Max 4”
Reinforced slabs, beams
-Min 5” Max 2”
Building columns
-Min 5” Max 3”
Pavements
-Min 2” Max 1”
Sidewalks, driveways
-Min 4” Max 2”
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UNIFORMITY &
WORKABILITY
• Uniformity refers to the thorough mixing of
all ingredients
• Workability refers to the ease which
concrete can be placed and shaped.
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QUALITIES OF HARDENED
CONCRETE
• Durability refers to resistance to chemical actions,
freezing, and thawing. Good workmanship and
proper mixing improves durability.
• Strength is measured as compressive and tensile.
Compressive strength is usually 10 times the
tensile strength of unreinforced concrete.
Additional reinforcement will equalize the
strength.
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Other Conditions
• Water-cement ratio, curing time, & curing
methods are just as important as reinforcement.
• Rule of thumb: Use a 5-7 gallons of water per
sack of cement. Exceeding this will weaken the
mix.
• Concrete cured for 7 days is only 2/3 as strong as
concrete cured for 28 days.
• Damp curing can increase as much as 50% for the
first 7 days.
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WATERTIGHTNESS
• The ability to prevent water passage
through the mass. The water-cement ratio
and curing time affect watertightness.
• Less water in the mix increases
watertightness.
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WEAR RESISTANCE
• The ability to resist abrasive action of
vehicles, feet, flowing water, etc.
• Aggregates should be hard and tough to
resist wear.
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READY MIXED CONCRETE
• Sold by cubic yard
• Two methods of mixing—transit mixer &
shrink-mixed
• Transit mixer is when mixing is done on the
truck
• Shrink-mixed begins in a stationary mixer
and ends up in a truck mixer.
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ADVANTAGES OF READYMIX
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Thoroughly mixed
Ingredients are not handled on the job site.
Less labor is required.
Exact quantity needed can be ordered.
Actual price can be calculated easily.
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ADMIXTURES
• Air-entraining –hundreds of microscopic air cell
are dispersed in the mix to protect during freezing
and thawing actions.
• Water-reducing –increases strength.
• Retarding –slows down the setting time during
high temperature.
• Accelerating –calcium chloride is added to mix to
shortened the set up time.
• Pozzolans –controls expansion during heat.
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ESTIMATING READY-MIX
CONCRETE
• Allows a 10% waste.
• When ordering mixtures by numbers: a 66-6 stands for 6 sacks of cement per cubic
yard, 6 gallons of water per sack of cement,
and 6 % entrained air.
• To determine surface area (length x width)
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CALCULATING READY-MIX
CONRETE
• Determine surface area.
• Determine the concrete thickness
• Refer to chart to determine the number of cubic
yards of concrete needed.
• Concrete thickness
Divide Area by:
1 inch
300
3 inches
100
4 inches
75
6 inches
50
12 inches
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RECOMMENDED MIXES
• 5-Gallon mix –for acid or alkaline resistant
walks, fence posts, flower boxes, & etc.
• 6-Gallon mix –for watertight floors, tanks,
walls and all reinforced concrete.
• 7-Gallon mix –for foundation walls,
retaining walls, underground concrete and
concrete not under water pressure.
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MOISTURE IN SAND
• Damp sand – ¼ gal/cu.ft (falls apart when
hand is opened.)
• Wet sand – ½ gal/cu.ft (ball of sand holds
shape when hand is opened.)
• Very wet sand – (3/4 gal/cu.ft (ball is
formed and leaves hand wet when opened.
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“FULLER’S” RULE
• Rule states – mixing of a total of 42
volumes of cement, sand, and gravel will
produce 27 volumes of concrete.
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FULLER’S RULE
• Use a 1 – 2-1/4 – 3 mix to build 4”thick, 6’
wide, and 100’ long sidewalk.
– Determine the amount of concrete required.
6’ x 100’ x 4” or 6’ x 100’ x 1/3’
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=200 cubic feet of concrete
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FULLER’S RULE
• Determine the amount of raw materials
needed.
200 X 42 =
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311 cu ft of raw materials
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FULLER’S RULE
• Determine the volume of mix needed.
1 + 2-1/4 + 3 = 6-1/4 (6.25) volumes of
mix
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FULLER’S RULE
• Determine the sacks of cement needed.
311 cuft. raw materials = 49.76 sacks
6.25 volume of mix
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FULLER’S RULE
• Determine the cu. yds. of sand needed.
50 sacks x 2.25 = 4.17 cu yds of sand
27 cu.ft/yd
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FULLER’S RULE
• Determine the cu yds. Of gravel needed.
50 sacks x 3 = 5.55 cu yds of gravel
27 cu ft/yd
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FULLER’S RULE SUMMARY
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200 cu feet of concrete required
311 cu ft of raw materials
6-1/4 or 6.25 volumes of mix
49.76 or 50 sacks of cement
4.17 cu yds of sand
5.55 cu yds of gravel
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MIXING CONCRETE
• Two common methods of mixing – machine and
hand mixing.
• Steps in machine mixing
-add 10% water before adding in solids.
-add portion of gravel.
-add measured amount of cement
-add sand and remaining amts of gravel
-mix from 1 – 3 minutes
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MIXING CONCRETE
• Steps in hand mixing
-place sand in mixing container
-then add cement and mix thoroughly
-add gravel and continue to mix
-add measured amounts of water
-mix thoroughly
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