TM 5-830-3/AFM 88-17, Chap. 3
with 1 to 5 or more parts water to one part emulsified
material will remain on the surface as an asphalt film that
asphalt by volume prior to use. As a general rule, a 3
is tacky at a ground temperature of approximately 100
part water to 1 part emulsion dilution is satisfactory for
degrees Fahrenheit and above. The APSB must be
most applications. The slow-setting cationic emulsions
heated to a temperature between 130 and 150 degrees
of grades CSS-1 and CSS-1h are easiest to use without
Fahrenheit to permit spraying with an asphalt distributor.
(2) Resinous materials.
These dust
dilution. If dilution is desired, the water used must be
free of any impurities, minerals, or salts that might cause
palliatives may be used as either surface penetrants or
separation (breaking) of the emulsion within the
surface blankets as they have a tendency to either
distribution equipment.
penetrate the surface or form a thin surface film
(c) Road tars.
Road tars (tars) are
depending on the type used, the soil type, and the soil
viscous liquids obtained by distillation of crude tars
condition. The materials are normally applicable to
obtained from coal. Tars derived from other basic
nontraffic areas and occasional traffic areas where
materials are also available, but are not normally used as
rutting will not occur. They are not recommended for use
soil treatments. Tars are graded by viscosity and
with silts and clays.
(a)
Resin-petroleum-water
emulsion.
available in grades ranging from 1 to 12. Tars are also
available in the cutback (RTCB) form of viscosity grades
Resin petroleum water emulsions are quite stable and
5 and 6, and in the emulsified form. Tar emulsions are
highly resistant to weathering. A feature of this type dust
difficult to prepare and handle. The low viscosity grades
palliative is that the soil remains readily permeable to
RT-1 and RT-2 and the RTCB grades can be applied at
water after it is treated. This type of product is principally
temperatures as low as 60 degrees Fahrenheit without
manufactured under the trade name Coherex.
The tar cutbacks generally have better
Application rates range from 0.33 to 0.5 gallon per
penetrating characteristics than asphalts and will
square yard. The material may be diluted 4 parts water
normally cure in a few hours. Tars will produce excellent
to 1 part concentrate for spraying. This material is
surfaces, but curing proceeds very slowly, and several
primarily suited for dry sandy soils and has been found to
days or even weeks may be required to obtain a
provide unsuitable results when used on silty and clayey
completely cured layer.
Tars are susceptible to
soils.
(b) Lignin. Lignin is a by-product of the
temperature changes and may soften in hot weather or
become brittle in cold weather.
manufacture of wood pulp. It is soluble in water and
(d) Asphaltic penetrative soil binder
therefore readily penetrates the soil. Its solubility also
(APSB). This commercial product is a special liquid
makes it susceptible to leaching from the soil; thus
application is repeated as necessary after rainfall. Lignin
asphalt composed of high penetration grade asphalt and
is readily available in the continental United States and
a solvent blend of kerosene and naphtha. It is similar in
certain other sections of the world, and has utility in
character to a standard low viscosity, medium curing
areas where dust control is desirable for short periods of
liquid asphalt, but differs in many specific properties.
time. It is not recommended for use where durability is,
The APSB is suitable for application to soils that are
an important factor. Application at a rate of 1 gallon per
relatively impervious to conventional liquid asphalts and
square yard of a resinous solution of 8 percent solid
emulsion systems. Silts and moderately plastic clays (to
lignin sulphite is recommended.
a plasticity index of 15) can be treated effectively. Curing
time for the APSB is 6 to 12 hours under favorable
ground temperature and weather conditions. On high
plasticity solids (plasticity index greater than 15), the
3-4
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