UFC 3-250-03
15 May 2001
emulsion. The current guide specification requires that the final FRS mixture developed be required to
meet several test requirements. The tests include curing time, resistance to heat, resistance to water,
resistance to kerosene, stiffness, and viscosity.
(2) Application rate. The rate of application of sealer will depend to a great extent on the
gradation of the aggregate used. The coarser the gradation, the thicker the application required. This
assures that the aggregate is embedded in the sealer and will not wear off under traffic. The rates given
are for general guidance and may vary depending upon the final proportions (solids content) of the
sealer that is applied.
(3) Requirements. The FRS mixture must meet the requirements as given in table 4-6. A
stiffness requirement is given in the current fuel-resistant sealer guide specification. The requirement for
stiffness is not applicable for coal tar emulsion sealers. The stiffness test should be required where an
alternate binder (i.e. an epoxy system) is used which may not be flexible enough for use as a sealer on a
flexible pavement. The amount of sand added to the FRS mixture should not exceed 480 to 720 grams
per liter (4 to 6 pounds per gallon) of coal tar emulsion. Sand loads of greater amounts will not normally
be fuel resistant and will fail the resistance to kerosene test. Higher sand loadings are usually only
possible through the use of polymer additives which increase the viscosity of the FRS mixture and can
hold the sand in suspension.
Table 4-6
Physical Properties of Sealer Mixtures
Referenced
ASTM
Property
Requirement
Test Method
Curing time, firm set
8 hours maximum
D 2939
Resistance to heat
No blistering, sagging or slipping
D 2939
Resistance to water
No blistering, loss of adhesion or tendency to
D 4866
re-emulsify
Resistance to kerosene
No penetration or loss of adhesion
D 4866
Viscosity of sealer
Viscosity shall be a minimum of 700 centipoises at
--
23EC 3EC (all constituents added excluding sand)
f. Equipment. Various types of hand-held squeegees, brooms, and other non-mechanical
equipment are needed on the typical FRS project. Small jobs can sometimes be completed with only
small mixers and hand-held squeegees. However, the basic equipment required for mechanical
application on a FRS project include a truck-mounted batch-mix machine, squeegee blades, power
broom, and front-end loader or fork truck. The truck mounted batch-mix machine is where the FRS
mixtures are proportioned and mixed and then taken to the project site and applied to the pavement
surface. FRS mixtures are always batch mixed and then applied, unlike slurry seals which are made in
a continuous mix operation. The batch-mix machine usually has a manufacturer supplied calibration
sheet showing the number of gallons per depth in the tank. The depth is usually monitored with a
marked dip stick. The squeegee blades apply the FRS material to the pavement surface. The power
broom cleans the pavement surface prior to application. The front end loader can be used for aggregate
handling; however, a fork lift is more often needed as bagged and manufactured aggregate is often
used.
4-10
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