TM
5-822-14/AFJMAN
32-1019
CHAPTER 1
INTRODUCTION
1-1. Purpose. This manual establishes criteria
e. Additive stabilization. Additive stabilization
for improving the engineering properties of soils
is achieved by the addition of proper percentages
used for pavement base courses, subbase courses,
of cement, lime, fly ash, bitumen, or combinations
and subgrades by the use of additives which are
of these materials to the soil. The selection of type
mixed into the soil to effect the desired im-
and determination of the percentage of additive to
provement. These criteria are also applicable to
be used is dependent upon the soil classification
roads and airfields having a stabilized surface
and the degree of improvement in soil quality
layer.
desired. Generally, smaller amounts of additives
are required when it is simply desired to modify
1-2. Scope. This manual prescribes the appropri-
soil properties such as gradation, workability, and
ate type or types of additive to be used with
plasticity. When it is desired to improve the
different soil types, procedures for determining a
strength and durability significantly, larger quan-
design treatment level for each type of additive,
tities of additive are used. After the additive has
and recommended construction practices for incor-
been mixed with the soil, spreading and compac-
porating the additive into the soil. It applies to all
tion are achieved by conventional means.
elements responsible for Army and Air Force
f. Modification. Modification refers to the stabi-
pavement and design construction.
lization process that results in improvement in
some property of the soil but does not by design
1-3. References. Appendix A contains a list of
result in a significant increase in soil strength and
references used in this manual.
durability.
1-4. Definitions.
1-5. Uses of Stabilization. Pavement design is
a. Soils. Naturally occurring materials that are
based on the premise that minimum specified
used for the construction of all except the surface
structural quality will be achieved for each layer
layers of pavements (i.e., concrete and asphalt) and
of material in the pavement system. Each layer
that are subject to classification tests (ASTM D
must resist shearing, avoid excessive deflections
2487) to provide a general concept of their engi-
that cause fatigue cracking within the layer or in
neering characteristics.
overlying layers, and prevent excessive permanent
b. Additives. Manufactured commercial products
deformation through densification. As the quality
that, when added to the soil in the proper quanti-
of a soil layer is increased, the ability of that layer
ties, improve some engineering characteristics of
to distribute the load over a greater area is
the soil such as strength, texture, workability, and
generally increased so that a reduction in the
plasticity. Additives addressed in this manual are
required thickness of the soil and surface layers
limited to portland cement, lime, flyash, and bitu-
may be permitted.
men.
a. Quality improvement. The most common im-
c. Stabilization. Stabilization is the process of
provements achieved through stabilization include
blending and mixing materials with a soil to
better soil gradation, reduction of plasticity in-
improve certain properties of the soil. The process
dex or swelling potential, and increases in durabil-
may include the blending of soils to achieve a
ity and strength. In wet weather, stabilization
desired gradation or the mixing of commercially
may also be used to provide a working platform
available additives that may alter the gradation,
for construction operations. These types of soil
texture or plasticity, or act as a binder for cemen-
quality improvement are referred to as soil modifi-
tation of the soil.
cation.
d. Mechanical stabilization. Mechanical stabili-
b. Thickness reduction. The strength and stiff-
zation is accomplished by mixing or blending soils
ness of a soil layer can be improved through the
of two or more gradations to obtain a material
use of additives to permit a reduction in design
meeting the required specification. The soil blend-
thickness of the stabilized material compared with
ing may take place at the construction site, a
an unstabilized or unbound material. Procedures
central plant, or a borrow area. The blended
for designing pavements that include stabilized
material is then spread and compacted to required
soils are presented in TM 5-822-5/AFM 88-7,
densities by conventional means.
Chap. 3, TM 5-825-2/AFM 88-6, Chap. 2, TM
1-1
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