TM 5-822-5/AFM 88-7, Chap. 1
frost areas. However, in addition to the procedures
18-14. Stabilization with Lime and with LCF.
for mixture design specified in TM 5-822-4, cured
a. Bound base. Soils containing only lime as the
specimens of cement-modified soil should be sub-
stabilizer are generally unsuitable for use as base
jected to the 12 freeze-thaw cycles in ASTM D 560
course layers in the upper layers of pavement sys-
(but omitting wire-brushing) or other applicable
tems in frost areas. Lime, cement, and a pozzolanic
freeze-thaw procedures. This should be followed by
material such as flyash may be used in some cases
determination of frost design soil classification by
to produce a cemented material of high quality that
means of standard laboratory freezing tests. The
is suitable for upper base course and that has
USACECRL in Hanover, NH, has the capability to
adequate durability and resistance to freeze-thaw
perform these tests. For cement-modified soil used
action. In frost areas, LCF mixture design will be
in the base course, the frost susceptibility, deter-
based on the procedures set forth in TM 5-822-4
mined after freeze-thaw cycling, should meet the
with the additional requirement that the mixture,
requirements set forth for base course in chapter 5
after freeze-thaw testing as set forth below, should
of this manual. If cement-modified soil is used as
meet the weight-loss criteria specified in TM 5-822-
subgrade, its frost susceptibility, determined after
4 for cement-stabilized soil. The procedures in
freeze-thaw cycling, should be used as the basis of
ASTM D 560 should be followed for freeze-thaw
the pavement thickness design if the reduced sub-
testing, except that the specimens should be com-
grade design method is applied.
pacted in a 6-inch diameter mold in five layers with
a 10-pound hammer having an 18-inch drop, and
18-16. Stabilization With Bitumen.
that the preparation and curing of the specimens
should follow the procedures indicated in TM 5-
Many different types of soils and aggregates can be
822-4 for unconfined compression tests on lime-
successfully stabilized to produce a high-quality
stabilized soil.
bound base with a variety of types of bituminous
b. Lime-stabilized soil. If it is economical to use
material. In frost areas the use of tar as a binder
lime-stabilized or lime-modified soil in lower layers
should be avoided because of its high temperature
of a pavement system, a mixture of adequate dura-
susceptibility. Asphalts are affected to a lesser
bility and resistance to frost action is still necessary.
extent by temperature changes, but a grade of as-
In addition to the requirements for mixture design
phalt suitable to the prevailing climatic conditions
of lime-stabilized and lime-modified subbase and
should be selected. Excepting these special condi-
subgrade materials set forth in TM 5-822-4, cured
tions affecting the suitability of particular types of
specimens should be subjected to the 12 freeze-
bitumen, the procedures for mixture design set forth
thaw cycles in ASTM D 560 (but omitting wire-
in TM 5-822-4 and TM 5-822-8 usually will ensure
brushing) or other applicable freeze-thaw pro-
that the asphalt-stabilized base will have adequate
cedures. This should be followed by determination
durability and resistance to moisture and freeze-
of frost-design soil classification by means of stand-
thaw cycles.
ard laboratory freezing tests. The USACECRL in
Hanover, NH, has the capability to perform these
18-17. Subgrade Requirements.
tests. For lime-stabilized or lime-modified soil used
It is a basic requirement for all pavements con-
in lower layers of the base course, the frost suscep-
structed in frost areas, that subgrades in which
tibility, determined after freeze-thaw cycling, should
freezing will occur, shall be prepared to achieve
meet the requirements set forth for base course in
uniformity of soil conditions by mixing stratified
chapter 5 of this manual. If lime-stabilized or lime-
soils, eliminating isolated pockets of soil of higher
modified soil is used as subgrade, its frost
or lower frost susceptibility, and blending the vari-
susceptibility, determined after freeze-thawing
ous types of soils into a single, relatively homoge-
cycling, should be used as the basis of the pavement
neous mass. It is not intended to eliminate from the
thickness design if the reduced subgrade strength
subgrade those soils in which detrimental frost
design method is applied.
action will occur, but to produce a subgrade of uni-
form frost susceptibility and thus create conditions
18-15. Stabilization with Portland Cement.
tending to make both surface heave and subgrade
Cement-stabilized soil meeting the requirements set
thaw-weakening as uniform as possible over the
forth in TM 5-822-4, including freeze-thaw effects
paved area. In fill sections the least frost-susceptible
tested under ASTM D 560, may be used in frost
soils shall be placed in the upper portion of the
areas as base course or as stabilized sub- grade.
subgrade by temporarily stockpiling the better ma-
Cement-modified soil conforming with the
terials, cross-hauling, and selective grading. If the
requirements in TM 5-822-4 also may be used in
upper layers of fill contain frost-susceptible soils,
18-16
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