REP04837

• Permit No: M1977342
• IBM Index Class Name: Report
• Doc Date: 9/28/2001
• Doc Name: CRUSHER CLOSURE CAP PLANS & SPECIFICATIONS RN 1 HENDERSON MILL PN M-77-342
• From: CLIMAX MOLYBDENUM CO
• To: DMG
• Media Type: D
• Archive: No

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CHAPTER I4
Control Tests for Quality Concrete
Satisfactory concrete construction and performance
requires concrete possessing specific properties. To as-
sure that these properties are obtained, quality control
and acceptance testing are indispensable parts of the
construction process. Past experience and sound judg-
ment must be relied on in evaluating tests and assess-
ing their significance in the ultimate performance of
the concrete.
CLASSES OF TESTS
In general, specifications for concrete and its compo-
nent materials give detailed requirements for limits of
acceptability. The requirements may affect (I) charac-
teristics of the mixture, such as maximum size of
aggregate or minimum cement content; (2) character-
istics ofthe cement, water, aggregates, and admixtures;
and (3) characteristics of the freshly mixed and hard-
enedconcrete, such as temperature, slump, air content,
or compressive strength.
Cements are tested for their compliance with estab-
lished standards to avoid any abnormal performance
such as early stiffening, delayed setting, or low strengths
in concrete.
Tests of aggregates have two major purposes: First.
to determine the suitability of the material itself for
use in concrete, including tests for abrasion, sound-
ness, specific gravity, and petrographic and chemical
analysis; second, to assure uniformity, such as tests for
moisture control and gradation of aggregates. Some
tests are used for both purposes.
Tests of concrete to evaluate the performance of
available materials, to establish mixture proportions,
and to control concrete quality in the field include
slump, air content, unit weight, and strength. Slump.
air content, and strength tests are usually required in
project specifications for concrete quality control,
whereas unit weight is used more in mixture propor-
tioning.
Following is a discussion of frequency of testing and
descriptions of the major control tests to ensure uni-
formity ofmaterials, desired properties of freshly mixed
concrete, and required strength of hardened concrete.
Special tests are also described.
FREQUENCY OF TESTING
Frequency of testing is a significant factor in the effec-
tiveness of quality control ofconcrete.
The frequency of testing aggregates wind concrete for
typical batch-plant procedures depends largely upon
the uniformity of materials, including the moisture
content of aggregates. Initially it is advisable to make
tests several times a day, but as work progresses the
frequency often can be reduced.
l3sually, moisture tests are made once or twice a day.
The first batch of fine aggregate in the morning is often
overly wet since moisture will migrate overnight to the
bottom of the storage bin. As fine aggregate is drawn
from the bottom, the moisture content should become
stabilized at a lower level and the first moisture test
can be made. After a few tests, changes in moisture
content can be judged fairly accurately by sight and by
feel. Subsequent tests are usually neces:cary only when
a change is readily apparent.
Slump tests should be made for the first batch of
concrete each day, whenever consistency of concrete
appears to vary, and whenever strengtlrtest cylinders
are made at the jobsite.
Air-content tests should be made often enough at the
point of delivery to ensure proper air content, particu-
larly if temperature and aggregate grading change. An
air-content test is desirable for each sample ofconcrete
from which cylinders are made; a record of the temper-
ature of each sample ofconcrete should also be kept.
.j,t~ pf.strength tests made wiJ#~pend on
t }06 specificattons and the occurrenct: of variations.
tldiag Cade Requirements for Reinforced Concrete
(_CI 318) specifies that strength tests of each class of
Concrete placed each day should be taken not less than
once a day, nor Jess than once for each 150 cu yd of
(~ncrete, nor less than once for each 5000 sq ft of
surface area for slabs or walls. The average strength of
.two cylinders is required for each test. Additional spec-
imens may be required when high-strength concrete is
involved or where structural requirements are critical.
The specimens should be laboratory cured. Specifica-
tions may require that additional specimens be made
and fiGld•cured, as nearly as practical in the same
manner a~the concrete in the structure. A 7-day test
cylinder, along with the two 28-day test cylinders, is
often made and tested to provide an early indication