CONCRETE CUBE TEST DEFINITION:
For Determining The Compressive Strength Of Concrete The Concrete Cube Test Is Conducted
This Test Give Us An Idea About All The Characteristic Of Concrete.
FACTOR ON WHICH COMPRESSIVE STRENGTH OF CONCRETE DEPENDS:
1) Water Cement Ratio
2) Cement Strength
3) Quality Of Concrete
4) Quality Control During Production Of Concrete etc.
APPARATUS FOR CUBE TEST:
1) Cube Mould
( 150MM X 150MM X 150MM)
2) Temping Rod
16MM Dia, 600MM Long With Bullet Head At Compaction End.
3) Scoop, Levelling Float, Big G.I Pan (Ghamela), Wheel Berrow, Coten Wast,
Mould Realising Oil, Steel Platform, Hassan Cloth, Measuring Tape.
PROCEDURE:
A) Preparation of Cube Moulds :
1) All internal faces especially at
edges and joints should be cleaned and free from hardened concrete, mortar,
dirt etc.
2) Oiling to be done for both inner and
outer side of cube moulds before casting of cubes.
3) Measure and verify correct
dimensions such as size and diagonal of cube moulds.
4) Place the moulds on hard and levelled
surface.
B) Sampling Of Concrete :
1) The concrete should be unloaded half
in the trolley below the mixer to take one pan of concrete and then unload
fully to take one more pan. Homogeneously mix the concrete in trolley before taking sample in the pan.
2) Sufficient quantity of concrete
should be taken for cube casting i.e. one big ghamela (Pan) per three cubes to be cast.
C) Casting of Cubes :
1) Mix sample homogeneously.
2) Cubes shall be filled in three
layers of approximately 50mm. Each layer shall be compacted with 35 blows of
standard tamping rod.
3) To avoid entrapment of air in the
corners and sides it is recommended to tamp the sides of moulds using wooden
mallet equally from all the sides or tamping can be done on the base plate using a tamping rod.
4) Finally trowel the surface level on
top of the mould.
5) After finally finishing the following
details to be marked on top of cube in the order as shown in the sketch :
i Grade of Concrete according to code given
for each grade. (M10-A, M15-B, M20-C,
M25-D,
M30-E, M35-F, M40-G, M45-H, M50-I,)
ii Cube Number
iii Name of Site
iv Structure
v Brand of Cement
vi Wing of building if any.
vii Date
|
i
|
ii
|
iii
|
|
iv
|
v
|
vi
|
|
vii
|
vii
|
vii
|
6) After finishing, the concrete cube
moulds shall be immediately covered with damp hessian
cloth till cubes are
placed in the curing tank.
7) Cast minimum 13 cubes for each pour
and each grade of concrete. Additional cubes may be cast
as per specific requirements.
D) Compression Testing of Concrete :
1) Minimum.
Number of cubes to be tested shall be as per the below-given table:
|
Sr.
No
|
Structure
|
3
Days
|
5
Days
|
7
Days
|
15
Days
|
28
Days
|
ACT
|
Extra
|
|
1
|
Footing
, Column, Retaining Wall, Pardi etc.
|
3
|
-
|
3
|
|
4
|
1
|
2
|
|
2
|
Plinth
Beam
|
-
|
-
|
3
|
3
|
4
|
1
|
2
|
|
3
|
Slab,
Staircase etc.
|
3
|
|
3
|
3
|
4
|
1
|
2
|
2) Cubes should be placed in CTM in such a way
that smooth faces of the cubes rest on steel surface and it shall be
concentric with the plate axis ( not eccentric).
3) Start
loading the cube and continue till no increase in load is observed.
4) Compression
strength of the specimen is calculated by dividing the failure load by the area of cross-section under the load.
5) Record
the test results indicating the
following details.
·
Building
·
Location
·
Structure
·
Grade of concrete
·
Casting date
·
Testing date
·
W/B ratio
·
Brand and grade of cement with lot
number
·
Cement content
·
Plasticizer ( make and quantity )
·
Any mineral admixture and quantity
per bag.
·
Slump
·
Load
·
Strength in kg/cm2
E) Sample Calculations:
Cross Sectional Area of Cube = 15cm x 15cm = 225 cm2.
Failure Load as indicated in Cube Testing Machine = 1200KN.
Compressive/ Crushing Strength = (1200 x 1000)/ 225 x 10 =
533.33 Kg/cm2.
F) Observation/ Conclusion :
Compressive /
Crushing Strength from above sample calculation = 533.33 Kg/cm2.
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