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. = cu. yards
27 cu. ft 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: = 7 2 cu. ft.
$       Number of batches = 311 cu. ft. =
7 2 cu. ft.
$       Sacks of cement = 1 (41.467) = or 42 sacks
$       Cu. ft. of fine aggregate (41.467) (2 2) = or 104 cu. ft.
$       Cu. ft. of coarse aggregate (41.467) (4) = 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 = cu.ft.
3.15 x
$                                           Fine Aggregate:
Absolute Volume = 2 2 cu. ft. x 100#/cu. ft. = 250 = cu.ft x

8. Estimating concrete for a job.
F. Absolute volume method.
$                       Coarse aggregate:
Absolute Volume = 4 cu. ft. x 100#/cu. ft. = 400 = cu.ft.
2.65 x
$                         Water:
Absolute Volume= 7/7 2 x 62.4 = 7/7 2 = cu. ft.
1 x 62.4

9. Estimating concrete for a job.
F. Absolute volume method.
$       Total volume of concrete per sack cement = 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) = or 148 cu. ft.
Water to add = 7-5/8=6 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
or 1/3 .33
5 5/
6 6/12 or
7 7/
or 2/3 .67
10 10/12 or 5/6 .83

11. 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. PROBLEM: How 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

15. WHAT WILL A 1 : 2 : 3 - 6 GALLON MIX YIELD?
-ABSOLUTE VOLUME
FT3 X % SOLIDS = FT3
Cement ______ 47 ______
Sand ______ 60 ______
Gravel ______ 55 ______
Water ______ ______
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