DIGITAL CONCRETE COMPRESSION TEST (200 TON)
ASTM C39, BS EN 12390
1. Scope*
1.1 This test method covers determination of compressive
strength of cylindrical concrete specimens such as molded
cylinders and drilled cores. It is limited to concrete having a
density in excess of 800 kg/m3 [50 lb/ft3].
1.2 The values stated in either SI units or inch-pound units
are to be regarded separately as standard. The inch-pound units
are shown in brackets. The values stated in each system may
not be exact equivalents; therefore, each system shall be used
independently of the other. Combining values from the two
systems may result in non-conformance with the standard.
3. Summary of Test Method
3.1 This test method consists of applying a compressive
axial load to molded cylinders or cores at a rate which is within
a prescribed range until failure occurs. The compressive
strength of the specimen is calculated by dividing the maximum
load attained during the test by the cross-sectional area of
the specimen.
4. Significance and Use
4.1 Care must be exercised in the interpretation of the
significance of compressive strength determinations by this test
method since strength is not a fundamental or intrinsic property
of concrete made from given materials. Values obtained will
depend on the size and shape of the specimen, batching, mixing
. Procedure
7.1 Compression tests of moist-cured specimens shall be
made as soon as practicable after removal from moist storage.
7.2 Test specimens shall be kept moist by any convenient
method during the period between removal from moist storage
and testing. They shall be tested in the moist condition.
7.3 All test specimens for a given test age shall be broken
within the permissible time tolerances prescribed as follows:
Test Age Permissible Tolerance
24 h 6 0.5 h or 2.1%
3 days 2 h or 2.8 %
7 days 6 h or 3.6 %
28 days 20 h or 3.0 %
90 days 2 days 2.2 %
7.4 Placing the Specimen—Place the plain (lower) bearing
block, with its hardened face up, on the table or platen of the
testing machine directly under the spherically seated (upper)
bearing block. Wipe clean the bearing faces of the upper and
lower bearing blocks and of the test specimen and place the test
specimen on the lower bearing block. Carefully align the axis
of the specimen with the center of thrust of the spherically
seated block.
7.4.1 Zero Verification and Block Seating—Prior to testing
the specimen, verify that the load indicator is set to zero. In
cases where the indicator is not properly set to zero, adjust the
indicator (Note 9). As the spherically seated block is brought to
bear on the specimen, rotate its movable portion gently by hand
so that uniform seating is obtained.
NOTE 9—The technique used to verify and adjust load indicator to zero
will vary depending on the machine manufacturer. Consult your owner’s
manual or compression machine calibrator for the proper technique.
7.5 Rate of Loading—Apply the load continuously and
without shock.
7.5.1 The load shall be applied at a rate of movement (platen
to crosshead measurement) corresponding to a stress rate on
the specimen of 0.25 6 0.05 MPa/s [35 6 7 psi/s] (See Note
10). The designated rate of movement shall be maintained at
least during the latter half of the anticipated loading phase.
NOTE 10—For a screw-driven or displacement-controlled testing machine,
preliminary testing will be necessary to establish the required rate
of movement to achieve the specified stress rate. The required rate of
movement will depend on the size of the test specimen, the elastic
modulus of the concrete, and the stiffness of the testing machine.
7.5.2 During application of the first half of the anticipated
loading phase, a higher rate of loading shall be permitted. The
higher loading rate shall be applied in a controlled manner so
that the specimen is not subjected to shock loading.
7.5.3 Make no adjustment in the rate of movement (platen to
crosshead) as the ultimate load is being approached and the
stress rate decreases due to cracking in the specimen.
7.6 Apply the compressive load until the load indicator
shows that the load is decreasing steadily and the specimen
displays a well-defined fracture pattern (Types 1 to 4 in Fig. 2).
For a testing machine equipped with a specimen break detector,