3.1.2.2
Testing Procedures
Strength test specimens for acceptance tests shall be molded and cured in
accordance with ASTM C 31/C 31M. Strength test specimens and testing for
mortar shall conform to ASTM C 109/C 109M. Cylinders shall be tested in
accordance with ASTM C 39/C 39M and beams shall be tested in accordance
with ASTM C 78. A strength test shall be the average of the strengths of
two specimens made from the same sample of concrete and tested at 28 days
or at another specified test age. Tests for total air content and slump
shall be made on fresh samples of the concrete and mortar. Tests shall be
performed on site, on samples taken at the location of placement.
Slump
shall be determined in accordance with ASTM C 143/C 143M. Air content
shall be determined in accordance with ASTM C 231. Testing for shrinkage
shall be determined in accordance with ASTM C 1107.
3.1.2.3
Evaluation of Results
Concrete and mortar shall have a compressive strength at 28 days as
determined by ASTM C 39/C 39M and ASTM C 109/C 109M respectively, which
matches the present compressive strength of concrete in the structure
within a tolerance of from -0 MPa to +3.5 MPa from -0 psi to +500 psi.
Concrete and mortar strengths will be considered satisfactory if the
averages of all sets of three consecutive strength test results equal or
exceed the specified strength and no individual strength test result falls
below the required strength. For flexural strength concrete, the strength
level of the concrete will be considered satisfactory if the averages of
all sets of five consecutive strength test results equal or exceed the
required flexural strength, and not more than 20 percent of the strength
test results fall below the required strength by more than 0.35 MPa 50 psi.
The required minimum strength shall be the strength determined from
testing of samples taken from the structure.
3.1.2.4
Investigation of Low-Strength Test Results
When any strength test of standard-cured test specimen falls below the
specified strength requirement by more than 3.5 MPa 500 psi, or if tests of
field-cured specimens indicate deficiencies in protection and curing, steps
shall be taken to ensure that load-carrying capacity of the structure is
not jeopardized. Nondestructive testing in accordance with ASTM C 597,
ASTM C 803/C 803M, or ASTM C 805 may be permitted by the Contracting
Officer to determine the relative strengths at various locations in the
structure as an aid in evaluating concrete strength in place or for
selecting areas to be cored. Such tests, unless properly calibrated and
correlated with other test data, shall not be used as a basis for
acceptance or rejection. When strength of concrete in place is considered
potentially deficient, cores shall be obtained and tested in accordance
with ASTM C 42/C 42M. At least three representative cores shall be taken
from each member or area of concrete in place that is considered
potentially deficient. The location of cores shall be determined by the
Contracting Officer to least impair the strength of the structure. If the
concrete in the structure is dry under service conditions, the cores shall
be air-dried (temperature 16 to 27 degrees C 60 to 80 degrees F, relative
humidity less than 60 percent) for seven days before testing and shall be
tested dry. If the concrete in the structure is more than superficially
wet under service conditions, the cores shall be tested after moisture
conditioning in accordance with ASTM C 42/C 42M. Concrete in the area
represented by the core testing will be considered adequate if the average
strength of the cores is equal to or at least 85 percent of the specified
strength requirement and if no single core is less than 75 percent of the
SECTION 03900
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