TM 5-822-5/AFM 88-7, Chap. 1
(9) Frost-susceptible soil is soil in which
pavement surfacing layer where its high strength
significant detrimental ice segregation will occur
and low deformability make possible a reduction in
when the requisite moisture and freezing conditions
the required thickness of the pavement surfacing
are present.
layer or the total thickness of pavement and base, or
(10) Granular unbound base course is base
both. If the stabilizing additive is portland cement,
course containing no agents that impart higher co-
lime, or lime-cement-flyash (LCF), the term bound
hesion by cementing action. Mixtures of granular
base is applicable only if the mixture meets the
soil with portland cement, lime, or flyash, in which
requirements for cement-stabilized, lime-stabilized,
the chemical agents have merely altered certain
or LCF-stabilized soil set forth herein and in TM 5-
properties of the soil such as plasticity and
822-4.
gradation without imparting significant strength
(3) Boulder heave is the progressive upward
increase, also are classified as granular unbound
migration of a large stone present within the frost
base. However, these must meet the requirements
zone in a frost-susceptible subgrade or base course.
for cement-modified, lime-modified, or LCF-modi-
This is caused by adhesion of the stone to the
fled soil set forth in TM 5-822-4 and in this chap-
frozen soil surrounding it while the frozen soil is
ter, and they must also meet the base course com-
under-going frost heave; the stone will be kept from
position requirements set forth below.
an equal, subsequent subsidence by soil that will
(11) Ice segregation is the growth of ice as
have tumbled into the cavity formed beneath the
distinct lenses, layers, veins and masses in soils,
stone. Boulders heaved toward the surface cause
commonly but not always oriented normal to the di-
extreme pavement roughness and may eventually
rection of heat loss.
break through the surface, necessitating repair or
(12) Nonfrost-susceptible materials are cohe-
reconstruction.
sionless materials such as crushed rock, gravel,
(4) Cumulative damage is the process by
sand, slag, and cinders that do not experience sig-
which each application of traffic load or each cycle
nificant detrimental ice segregation under normal
of climatic change produces a certain irreversible
freezing conditions. Nonfrost-susceptible materials
damage to the pavement. When this is added to
also include cemented or otherwise stabilized ma-
previous damage, the pavement deteriorates con-
terials that do not evidence detrimental ice segre-
tinuously under successive load applications or cli-
gation, loss of strength upon thawing, or freeze-
matic cycles.
thaw degradation.
(5) Frost action is a general term for freezing
(13) Pavement pumping is the ejection of
and thawing of moisture in materials and the re-
water and soil through joints, cracks, and along
sultant effects on these materials and on structures
edges of pavements caused by downward move-
of which they are a part, or with which they are in
ments of sections of the pavement. This is actuated
contact.
by the passage of heavy axle loads over the pave-
(6) Frost boil is the breaking of a small
ment after free water has accumulated beneath it.
section of a highway or airfield pavement under
(14) Period of weakening is an interval of the
traffic with ejection of soft, semi-liquid subgrade
year that starts at the beginning of a frost-melting
soil. This is caused by the melting of the segregated
period and ends when the subgrade strength has
ice formed by the frost action. This type of failure is
returned to normal summer values, or when the
limited to pavements with extreme deficiencies of
subgrade has again become frozen.
total thickness of pavement and base over frost-
b. Temperature terms.
susceptible subgrades, or pavements having a highly
(1) Average daily temperature is the
frost-susceptible base course.
average of the maximum and minimum
(7) Frost heave is the raising of a surface due
temperatures for a day, or the average of several
to formation of ice in the underlying soil.
temperature readings taken at equal time intervals,
(8) Frost-melting period is an interval of the
generally hourly, during a day.
year when the ice in base, subbase, or subgrade
(2) Mean daily temperature is the mean of
materials is returning to a liquid state. It ends when
the average daily temperatures for a given day in
all the ice in the ground has melted or when freezing
each of several years.
is resumed. In some cases there may he only one
(3) Degree-days are the Fahrenheit degree-
frost-melting period, beginning during the general
days for any given day equal to the difference
rise of air temperatures in the spring, but one or
between the average daily air temperature and 32
more significant frost-melting intervals often occur
degrees Fahrenheit. The degree-days are minus
during a winter season.
18-3
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