COMPRESSIVE STRENGHT by carthi

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COMPRESSIVE STRENGHT OF
HARDEN CONCRETE:

Objective:
To calculate the compressive strength

Introduction :

Result of testing concrete for strength is subject to
many variables . Concrete is made from different
material, by different method, and in different mix
proportion and is tested by different procedure .
Actually, these are all reasons why concrete must be
tested in a regular pattern during a job rather than
just once at the beginning .
The usual procedure is to cast test specimen as a
structure is placed, the measure of strength shown by
the test specimen is not a true picture of the concrete
strength. Test specimen are cured differently from
the structure and so do not reflect the workshop that
goes into the structure. The test is valuable as an

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approximation of actual strength, a test of potential
quality as delivered. Such tests keep batches of
concrete uniform throughout the job. Concrete is
usually proportioned for a given compressive
The test of compressive strength is one of the most
frequently used cylinder or cubes are taken and
tested at specified ages. Test specimens may show
different results depending on their moisture content,
temperature, lateral restraint, and many other
variables.
Standard :
B.S 1881 : PART3 : 1970
ASTM : C 39-72
C 192-69
C 470-76

Apparatus :

•   Cube mould’s (15x15x15) cm .
•   Compaction bar .
•   Cylinders mould’s .
•   Rod .
•   Curing tank .
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Calculation :

Sample no.
1           2      3
Sample type
cube         cube        cube   cube
Age of sample
Days           7           7      7
Sample’s
length
mm            150         150    150
Sample’s
width
mm         150         150     150
Sample’s
height
mm         150         150     150
Sample cross-
section area
cm2        225         225     225
Sample’s
volume
cm3        3375        3375   3375
sample’s
weight
g       6755        6749   6879
Sample’s
density
g/cm3        2.27        2.00   2.04
Kg          37716.62 35372.07 41284.40
Compressive
strength
Kg/cm2        167.63   157.21   183.50

Ave .compressive strength =169.45

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Sample no.
1          2          3
Sample type
cylinder    cylinder   cylinder   cylinder
Age of sample
Days          7          7          7
Sample’s
length
mm          150        150        150
Sample’s
height
mm       300        300        300
Sample cross-
section area
cm2    176.71     176.71     176.71
Sample’s
volume
cm3    5301.44    5301.44    5301.44
sample’s
weight
g      -          -          -
Sample’s
density
g/cm3       -          -          -
Kg        23751.27 26095.82 19266.06
Compressive
strength
Kg/cm2      134.41   147.68   109.03

Ave .compressive strength =130.4
( ave.comp.st.cylinder )/( ave.comp.st.cube ) =
(130.4/169.45 )=0.77 ~ 0.8 relation .

Discussion and conclusion :
Compressive strength specimens are placed in an
apparatus that applies force on both ends until
failure.
Concrete is made from different material, also we
can tested it by different method.

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The number of strokes per layer required to produce
full compaction will vary according to the type of
concrete, but in no case shall it be less than 25 strokes
per layer .

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