To Determine the flexural Strength of Prism and also
Determine. The Equivalent cube strength.
1.
Eqypt/Material:
Cone mixer,
steel trays, weighing Balance, Vibrating table, Flexural testing machine with
third-point loading arrangement, compression testing machine, jig, prism/beam
mould(4” * 4 “ * 16”), trowel . folats,c/agg,f/agg. Cement, water and graudated
glass cylinder.
2.
Procudure:
a.
Flexerual
Strength:
(1)
Prepare
the concrete with given or reqd proportion in reqd volume.
(2)
Prepare
the reqd number of specimens and fill the concrete mix into the molds in two
layers with the help of viberating table.
(3)
De-
mold the specimens alter 24 hours and cure it in curing tankk for 28 days.
(4)
After
28 days take out the specimens from the curing tank and mark the loading points
and supports on the specimen. Before marking turn the test specimen on its side
with respect to its position as molded/ casted.
(5)
Place
the specimen in the testing machine and bring the load applying block in
contact with the surface of the specimen at third- point between the suppors.
(6)
There
after apply the load cintionuly at the rate of 125-175 psi/min until the
ruputre occurs. Note down the load/reading.
b.
Calculation:
If
the fracture occurs with in the middle third distance then the flexural
str/modulus of reputure = PL/ bd2 where p is the max load on prism, L= Span
length inch /mm, b = width of peism inch/mm, d = Depth of prism. If the
fracture occuresout side the loading points say at a distance ‘a’ from the
nearest point then the Modulus of reputure = 3 Pa/bd2.
c.
Equivalent
cube strength :
(1) Take the broken portion of the prism/bcam.
The length of broken portion of beam selected
for equivalent cube str shall be at least 2
in greater then the width.
(2) Set this
portion in the jig and keep this whole assembly in the centre of the
compression testing machine.
(3) Apply the
load continously and without shock. The moving head of the serew type of testing
machine shall travel at the rate of approx 0.05 in /min (.3mm/min) and
in hydraulic machine, the
loading shall be adjust to a constant rate with in the limits of 35- 15 psi/min.
(4) Record the
total load indicated by the testing machine at failure of the test specimen.
The comp str. Can be
calculated as comp str = P/A where P
is the load and A= Area of specimen.
3. Precautions:
a. Ensure the volume calculation of pouring is
sufficient and the prism molds should be oiled
before filling.
b. Load should be applied without shock and at a
specified rate.
c.
Broken portion of prism selected for comp
test shall be at least 2 inch greater than the width
of the prism
d. The selected portion of prism for comp test
shall be free from cracks and other obvious defects.
Details of reading / obsns/ data to be
recorded/collected
a.
Identification Mark=
b.
Date of casting=
c.
Date of testing=
d.
Size of Span=
e.
Size of specimen=
5. Flexural STR/ Modulus of Rupture
|
S/NO.
|
Max load
(KN)
|
Modulus of Rupture
|
Average
|
Remarks
|
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1
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2
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3
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6. Equivalent cub strength
|
S/NO.
|
Load (T)
|
Area
|
Comp Strength (Psi)
|
Average
|
Remarks
|
|
1
|
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2
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3
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4
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7. Interpretation / collection of absns
readings graphs etc leading to the results
To be done with the standard specification of ASTM C
78-94 ASTMC 116-90
8. Comments
a.
b.
c.
d.
Feel free to write