Compression Test of Concrete Cylinders

bulgefetaUrban and Civil

Nov 29, 2013 (3 years and 7 months ago)

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Compression Test of Concrete Cylinders


Purpose:

To determine the compressive strength of concrete.


Related Standards:

ASTM C39, C192, C617


Equipment:

Concrete molds, tamping rod, mallet, trowel, scoop, compression test
machine


Sample:

Concrete mixed as

follows:

1.

In a damp, watertight pan, mix the cement and fine aggregate (sand).

2.

Add the coarse aggregate and mix the entire batch without the addition of


water until the coarse aggregate is uniformly distributed throughout the



base.

3.

Add water
and mix until the concrete is homogeneous in appearance.


Procedure:


1.

Place the concrete in the molds using a scoop, trowel, or shovel.

2.

Distribute the concrete inside the mold using a tamping rod prior to consolidation.

3.

Fill the mold in three equa
l layers, rodding each layer 25 times using a 5/8
-
in.

tamping rod.

4.

Tap the sides of the mold gently with a mallet to close any voids.

5.

Finish the top surface by striking it off with the tamping rod.

6.

To

prevent evaporation of water, cover the speci
men immediately after finishing

with a sheet of impervious plastic or wet burlap.

7.

Remove

the specimen from the mold not less than 20 h
.

nor more than 48 h after

casting.

8.

Moist cure the specimens at 73.4 ±
3

o
F
(23 ±
o
C)
from the time of molding unt
il

the moment of test. Specimens will be tested at 7 and 28
-
day curing times.

9.

The ends of the specimens that are not plane within 0.002
-
in. should be capped.

10.

Compression tests are made as soon as practicable after removal from moist

storage. The

specimens are tested in moist condition.

11.

Wipe clean the bearing faces of the upper and lower bearing blocks and of the test

specimen.

12.

Place the specimen on the lower bearing block.

13.

Carefully align the axis of the specimen with the center of t
hrust of the spherically

seated upper block.

14.

Bring the upper block to bear on the specimen. Adjust the load to obtain uniform

seating.

15.

Apply the load at a loading rate of 20
-
50 psi/s. Time to failure for 3000
-
psi

concrete is 1
-
2.5 min, and for

6000
-
psi concrete is 2
-
5 min.

16.

Apply the load until the specimen fails.


Report:

Record the maximum load. Note the type of failure and the appearance of
the concrete (see p. 212 of Somayaji). Calculate the compressive strength as the average
of three

specimens.