Estimating Concrete Construction and Material Cost

1
Estimating Concrete Construction and Material
Cost
2
Concrete weights and measures.

• A. One sack of cement 94 pounds or one cubic
  foot
• B. One gallon of water 8.3 pound
• C. 7.5 gallons of water 1 cubic foot
• D. One cubic yard 27 cubic feet
• E. One cubic foot of sand weighs about 100
  pounds
• F. One cubic foot of gravel weighs about 100
  pounds

3
Estimating concrete for a job.

• A. The unit of measure for concrete is the cubic
  yard, which contains 27 cubic feet.
• B. To determine the needed amount of concrete,
  find the volume in cubic feet of the area to be
  concreted and divide this figure by 27.
• C. Formula for determining the amount of concrete
  needed for any square or rectangle area
• Cubic yards of concrete
•  
• Width in feet x length in feet x thickness in
  feet
• 27

4
Estimating concrete for a job.

• Example a 4" thick floor for a 30 x 60 ft.
  building would require
• 30' x 60' x 1/3' 600 cu. ft. 22.22 cu. yards
• 27 cu. ft. 27 cu. ft.

5
Estimating concrete for a job.

• D. The determined amount of concrete must allow
  for waste or slight variation in concrete
  thickness. An additional five to 10 percent
  will be needed to cover waste and other
  unforseen facts.

6
Estimating concrete for a job.

• E. Fuller method
• It takes 42 parts of materials to make 27 parts
  of cement.
•        Volume 200 cu. ft.
•        Cu. ft. of raw materials needed 42/27 (
  200 cu ft.) 311 cu. ft.
•        Cu. ft. of raw materials per batch 12 2
  4 7 2 cu. ft.
•        Number of batches 311 cu. ft. 41.467
• 7 2 cu. ft.
•        Sacks of cement 1 (41.467) 41.467 or
  42 sacks
•        Cu. ft. of fine aggregate (41.467) (2 2)
  103.66 or 104 cu. ft.
•        Cu. ft. of coarse aggregate (41.467) (4)
  165.86 or 166 cu. ft.
•        Water to add per batch 7-5/8 6 3/8
  gals.

7
Estimating concrete for a job.

• F. Absolute volume method.
•                                           
  Formula
• Absolute Volume Weight of loose materials
• Specific gravity x unit
  wt. of water
•                                           
  Cement
• Absolute Volume 1 cu. ft. x 94 lbs./cu. ft.
  94 0.478 cu.ft.
• 3.15 x 62.4 196.56
•                                            Fine
  Aggregate
• Absolute Volume 2 2 cu. ft. x 100/cu. ft.
  250 1.540 cu.ft.
  2.6 x 62.4 162.24

8
Estimating concrete for a job.

• F. Absolute volume method.
•                        Coarse aggregate
• Absolute Volume 4 cu. ft. x 100/cu. ft. 400
  2.480 cu.ft.
• 2.65 x 62.4 165.3
•                          Water
• Absolute Volume 7/7 2 x 62.4 7/7 2 0.933
  cu. ft.
• 1 x 62.4

9
Estimating concrete for a job.

• F. Absolute volume method.
•        Total volume of concrete per sack cement
  5.431 cu. ft.
•        Cement 1 (200/5.43) 36.8 or 37 sacks
•        Fine aggregate 2 2 (200/5.43) 92.1 or
  93 cu. ft.
•        Coarse aggregate 4 (200/5.43) 147.2
  or 148 cu. ft.
• Water to add 7-5/86 3/8 gallons per batch

10
Estimating concrete for a job.

• Changing the thickness in inches to fractions and
  decimal parts of a foot. For calculating
  quantities of concrete use the following table.
• Inches Fractional Part of Foot Decimal Part of
  Foot
• 4 4 2 or 1/3 .33
• 5 5/12 .42
• 6 6/12 or 2 .50
• 7 7/12 .58
• 8 8 12 or 2/3 .67
• 10 10/12 or 5/6 .83
• 12 1 1.00

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CONCRETE WEIGHTS AND MEASURES

• 1 Sack of Cement 94 pounds
• 1 Cubic Foot
•  
• 1 Gallon of Water 8.3 pounds
•  
• 7.5 Gallons of Water 1 Cubic Foot
•  
• 1 Cubic Yard 27 Cubic Feet
• 1 Cubic Foot of Sand Weighs About 100 Pounds

12
PROBLEMHow many square feet will a cubic yard
of concrete cover if it is placed 4 inches thick?
13
There are 27 Cubic Feet in 1 Cubic Yard   Each
Cubic Foot May Be Divided Into Three Volumes 4
Inches Deep and 1 Foot Square    
 
14
THE CONCRETE MIX YIELDS OF CONCRETE

• 1. Rule of Thumb
• Yield Equals 60 Percent of Volume
• 2. Absolute Volume
• Cement 47 Solids
• Sand 60 Solids
• Gravel 55 Solids
• Water 100 Solids

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WHAT WILL A 1 2 3 - 6 GALLON MIX YIELD?

• -ABSOLUTE VOLUME
• FT3 X SOLIDS FT3
• Cement ______ 47 ______
• Sand ______ 60 ______
• Gravel ______ 55 ______
• Water ______ 100 ______
•  
• TOTAL YIELD (FT3) ______
• (YARD3) ______
•  
• MIXES ______
• YARD3

16
HOW MANY BAGS OF CEMENT ARE NEEDED TO MIX 1
CUBIC YARD OF CONCRETE USING A 1 2 3 - 6
GALLON MIX?

• (Rule of thumb)
•  
• Yield _______ YD3 FT3/MIX
• 27 FT3/YARD3
•  
• 1 CUBIC YARD _______1 BAG MIXES
• YARD3/MIX
•  
• USE________BAGS OF CEMENT

17
WHAT WILL A 1 2 3 - 6 GAL. MIX YIELD?

• FT3
• Cement ________
• Sand ________
• Gravel ________
• Water ________
• Total ________ FT3
• x 60 ________ FT3
•  
• Yard3 ________
• Mix
•  
• Mixes ________
• Yard3
•  
• CALCULATED BY THE RULE OF THUMB