Determining Moisture-Unit Weight Relations of Soil (Compaction Test) - Soil Properties: Testing, Measurement, and Evaluation - page 166

The usual practice in a construction project is to perform labora-
tory compaction tests on representative samples from the construction
site to determine the optimum moisture content and maximum dry
unit weight. The maximum dry unit weight is used by designers in
specifying design shear strength, resistance to future settlement, and
permeability characteristics. The soil is then compacted by field com-
paction methods to achieve the laboratory maximum dry unit weight
(or a percentage of it). In-place soil unit weight tests (discussed in
Chapters 14, 15, and 16) are used to determine if and when the labora-
tory maximum dry unit weight (or an acceptable percentage thereof)
has been achieved.
A common compaction test is known as the Standard Proctor test .
The exact procedure for conducting a Standard Proctor test is described
later in this chapter, but the basic premise of the test is that a soil
sample is compacted in a 4- or 6-in. (101.6- or 152.5-mm) diameter mold
by dropping a 5.5-lb (24.4-N) hammer onto the sample from a height of
12 in. (305 mm), producing a compactive effort of 12,400 ft-lb/ft 3
(600 kN-m/m 3 ). An alternative test, known as the Modified Proctor test ,
uses a 10-lb (44.5-N) hammer that is dropped 18 in. (457 mm). The lat-
ter produces greater compaction and, hence, greater soil unit weight (be-
cause the hammer is heavier, drops farther, and therefore exerts greater
compaction effort on the soil sample). Therefore, the Modified Proctor test
may be used when greater soil unit weight is required. Only the Standard
Proctor test is described in detail in this topic. For details regarding the
Modified Proctor test, the reader is referred to ASTM D 1557 [2].
Three alternative methods are provided for carrying out a Stan-
dard Proctor test [2]:
(1) Method A:
(1.1) Mold —4-in. (101.6-mm) diameter.
(1.2) Material —Passing No. 4 (4.75-mm) sieve.
(1.3) Layers —Three.
(1.4) Blows per layer —25.
(1.5) Use —May be used if 20% or less by mass of the material is
retained on the No. 4 (4.75-mm) sieve.
(1.6) Other Use —If this method is not specified, materials that
meet these gradation requirements may be tested using Methods
B or C.
(2) Method B:
(2.1) Mold —4-in. (101.6-mm) diameter.
(2.2) Material —Passing 3 ⁄ 8 -in. (9.5-mm) sieve.
(2.3) Layers —Three.
(2.4) Blows per layer —25.