Lesson 4: Estimating Concrete Construction and Material Cost

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Georgia Agriculture Education Curriculum







Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

1

Course:

01.421

Agriculture Mechanics Technology

Unit 6:

Concrete Construction


Lesson 4:

Estimating Concrete Construction
and Material Cost



QCC:

................................
................................
................................
..............

227, 234, 235, 242


Objectives:

1.

Differentiate the notations and symbols on plans and
specifications for c
oncrete.

2.

Apply the procedure for determining concrete in cubic yards.

3.

Identify the importance of estimating waste allowance.

4.

Apply precision skills with measuring tools.

5.

Explain the requirement for accuracy of measurement and
estimates.

6.


Int
erpret the building plans and specification regarding
concrete mix ratio and quality.






Teaching Time:

Classroom:
110 minutes per period

Laboratory:

55 minutes


References:

Portland Cement Association. Skokie, IL.

Cooper, Elmer L.
Agricultural Mec
hanics: Fundamentals and Applications
. Delmar
Publishers, Inc. Albany, NY.

Burke, Stan & T.J. Wakeman.
Modern Agricultural Mechanics
. Interstate
Publishers, Inc. Danville, IL.



Materials and Equipment:

Fine aggregate, coarse aggregate, water, form O
il, concrete forms (molds),

Quart Jar (testing sand for silt or clay content), wheel barrow, CaCl (Calcium
Chloride), Portland or Medusa
Cement



Overhead Projector

Transparencies 6.4.1
-

6.4.7

Georgia Agriculture Education Curriculum







Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

2

T
EACHING
P
ROCEDURE


Introduction and Mental Set

A fellow tea
cher has requested that your class replace the sidewalk between
his garage and the service entrance of his home. Since this activity is a part
of your curriculum, you and the class agree to help this teacher.


What information do we need to know in orde
r to successfully estimate the
materials and costs?

What materials will we need?

Where can we purchase the materials?

What are the costs of the basic materials?

How much concrete do we need to complete the job?

When does the work need to be completed?


Dis
cussion


1.

Concrete weights and measures.
Use Transparency 6.4.1.

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 wei
ghts about 100 pounds

F.

One cubic foot of gravel weights about 100 pounds


2.

Estimating concrete for a job.
Use Transparency 6.4.2 and 6.4.3.

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

Georgia Agriculture Education Curriculum







Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

3

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.



D.

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

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 ( 20
0 cu ft.) =

31
1
cu.
ft.

$

Cu. ft. of raw materials per batch: 1+2
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.

F.

Absolute volume method. Use Transparencies 6.4.4
-
6.4.7.

$

Formula:


Absolute Volume =
Weight of loose materials

Specific gravity x unit wt. of water

$

C
ement:


Absolute Volume =
1 cu. ft. x 94 lbs./cu. ft.

=
94

=


3.15 x 62.4


196.56


.478 cu. ft.




$

Fine Aggregate:


Absolute Volume =

2
2

cu. ft. x 100#/cu. ft.

=
250

=



2.6 x 62.4
162.24


1.540 c
u. ft.



$

Coarse aggregate:


Absolute Volume =
4 cu. ft. x 100#/cu. ft.
=
400

=


2.65 x 62.4


165.3

2.480 cu. ft.

$

Water:


Absolute Volume
= 7/7
2

x 62.4

= 7/7
2

= .933 cu. ft.


1 x 62.4

$

Total
volume of concrete per sack cement = 5.431 cu. ft.

$

Cement = 1 (200/5.43) = 36.8 or 37 sacks

Georgia Agriculture Education Curriculum







Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

4

$

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
-
5/8=6 3/8 gallons per batch

G.

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


H.

For the materials needed per cubic yard of concrete made with
separate aggregates see the attached sheet.

I.

concrete estimating short cuts


3.

Determining materials for a concrete job.

A.

8/10 m
ethod

B.

Fuller
=
s method

C.

Absolute volume method

Example Problem:

Figure materials for a walk 4" thick, 6' wide and 100' long.

Water/Cement ratio of 7/1

Damp fine aggregate

Suggested mixture ratio:

Cement: Fine Aggregate: Coarse Aggregate in cu. ft.

Rat
io:

1:2 1/2:4 cu. ft.

$

8/10 method:

-

Volume
-

thickness x width x length

-

Coarse Aggregate = 8/10 x volume

-

Cement = ratio of coarse aggregate

-

Fine Aggregate = 2
2

x 40 sacks of cement = 100 cu. ft.

-

Water to add per sack = 7 gallons less than the wa
ter in
the fine aggregate. Water in fine aggregate = 1/4 x 2
2

=
5/8 gallons. Water to add = 7
-
5/8 = 6 3/8 gallons per
batch.

4.

Activities

A.

Lead the class in a discussion on the weights and measures
used in the concrete industry. Have students recor
d the units
of measure in their notebooks for future reference in this
course. Show transparency on concrete units of measure
(
Modern Agricultural Mechanics
, Wakeman, Pages 444).

Georgia Agriculture Education Curriculum







Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

5

B.

Lead the class in discussion on the proper procedure for
estimating the a
mount of concrete that is needed for a job.
Give students an example in class. Place students in groups
and have each group measure an area of concrete on campus
and let each group figure the amount of concrete needed to
pour the area measured. Make sur
e the students understand
the procedure for calculating the amount of concrete needed for
these jobs. Give students a list of areas to figure for practice.
Use handout on shortcut on figuring the amount of concrete
needed for certain thickness of concret
e. Use transparencies
for explaining the section (
Agricultural Mechanics,
Fundamentals and Application
, Cooper, Pages 402
-
403).

C.

Lead the discussion on the methods used in calculating the
amounts of materials needed for a prescribed concrete mixture.
E
xplain in detail the three methods used in calculating the
amount of materials needed for a concrete mixture. Give
students the formulas for each method used in figuring the
amount of materials needed. Use the example methods. Have
students use these me
thods to figure the amount of materials
needed to pour a patio block 1' x 1' x 2
2
" to be used at a later
date.

Georgia Agriculture Education Curriculum







Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

6

S
UMMARY


The instructor should emphasize the importance of precise
measurements in the production of concrete products. To illustrate
the impo
rtance of proper measurements and correct ingredients, it can
be compared to making a cake. The recipe for making a cake can be
considered the same as the correct concrete mixture to use and the
amounts of ingredients used in concrete jobs. It is extreme
ly
important for concrete quality to be maintained at all times, therefore,
the measurement of materials used must be accurate.



Evaluation


The students will be evaluated on the problems assigned in class as
well as the project of figuring the ingredient
s for the patio block. A
written test will be given over materials covered in class.


Georgia Agriculture Education Curriculum







Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

7

6.4.1


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 Ya
rd



=

27 Cubic Feet


1 Cubic Foot of Sand Weighs About 100
Pounds




Georgia Agriculture Education Curriculum







Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

8

6.4.2


PROBLEM:


How many square feet will a cubic yard of
concrete cover if it is placed 4 inches thick?



Georgia Agriculture Education Curriculum







Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

9

6.4.3



There are 27 Cubic Feet in 1 Cubic Yard


Each Cubic Foot May Be D
ivided Into Three
Volumes 4 Inches
Deep and 1 Foot
Square








Georgia Agriculture Education Curriculum







Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

10

6.4.4



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


10
0% Solids


Georgia Agriculture Education Curriculum







Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

11

6.4.5


WHAT WILL A 1 : 2 : 3
-

6 GALLON MIX YIELD?


-
ABSOLUTE VOLUME



FT
3

X % SOLIDS = FT
3



Cement

______



47

______


Sand


______



60

______


Gravel

______




55

______


Water

______




100______



TOTAL YIELD (FT
3
)

______


(YARD
3
)





___
___


MIXES






______

YARD
3




Georgia Agriculture Education Curriculum







Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

12

6.4.6


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



=_______

YD
3
=

FT
3
/MIX


27 FT
3
/YARD
3



1 CUBIC YARD

=_______1 BAG MIXES

YARD
3
/MIX





USE________BAGS OF CEMENT


Georgia Agriculture Education Curriculum








Course: 01.421


Agriculture Mechanics Technology


Unit 6, Lesson 4

Revised August 1999

13

6.4.7


WHAT WILL A 1 : 2 : 3
-

6 GAL. MIX YIELD?



FT
3


Cement




________

Sand





________

Gravel





________

Water





________

Total





________ FT
3

x 60%





________ FT
3


Yard
3





________

Mix


Mixes





________

Ya
rd
3


CALCULATED BY THE
RULE OF THUMB