Table 15-4.-Recommended Slumps for Various Types of Construction
Slump, inches*
Types of construction
Maximum
Minimum
Reinforced foundation walls and footings
Plain footings, caissons, and substructure walls
Reinforced slabs, beams, and walls
Building columns
Pavements
Heavy mass construction
Bridge decks
Sidewalks, driveways, and slabs on ground
5
4
6
6
3
3
4
6
2
1
3
3
2
2
3
3
*When high-frequency vibrators are used, the values may be decreased approximately one-third;
in no case should the slump exceed 6 inches.
gradation; specific gravity, absorption, and sur-
face moisture; impurities, such as organic
material, clay, or other water-absorbing particles;
and soundness, which is the property of an
aggregate to resist disintegration due to freezing
and thawing. Although these tests are not included
in this TRAMAN, you may refer to NAVFAC
MO-330, Materials Testing, should you desire to
learn more about them.
Slump Tests
As you are aware from your study of chapter
7, WORKABILITY is the relative ease or diffi-
cult y of placing and consolidating concrete. When
placed, all concrete should be as stiff as possible,
yet maintain a homogeneous, voidless mass. Too
much stiffness, however, makes it too difficult or
impossible to work the concrete into the forms
and around reinforcing steel. On the other hand,
too fluid a mixture is also detrimental. The mea-
sure of the workability or consistency of concrete
is its slump, which is a design consideration that is
inversely proportional to the stiffness of the mix.
As shown in table 15-4, the recommended values
for slump vary for different types of construction.
To measure slump, either during the preparation
of concrete trial batches or as a quality control
check during construction, testers perform slump
tests. The procedures for performing slump tests
will be explained later in this chapter.
Strength Tests
In the design of concrete structures, the design
engineer specifies given strengths that the final
concrete products must be capable of attaining.
When trial batches are prepared during mix design
or as a quality control measure to ensure that con-
crete mixed or delivered in the field satisfies those
specified strengths, the following tests are
performed.
COMPRESSION TEST.— Compression tests
are conducted to determine the compressive
strength of concrete (or its ability to resist a
crushing force). In this test, a standard test load
is applied parallel to the longitudinal axis of a
premolded and properly cured concrete cylinder
of a standard size. When the testis properly con-
ducted, a maximum load is obtained at the point
at which the cylinder ruptures. With this max-
imum load, the compressive strength, measured
in pounds per square inch (psi), can be easily
calculated. Although the test procedures will be
covered at the EA2 level, the procedures used to
prepare the cylinders for testing will be discussed
later in this chapter.
FLEXURAL STRENGTH TEST.— The flex-
ural strength (modulus of rupture) test determines
the flexural strength of concrete (or its ability to
resist a breaking force). In this test, a standard
15-35
