UFC 3-250-03
15 May 2001
g. Surface preparation. All loose material should be removed from the pavement surface prior to
application of the FRS. Cracks wider than 3 millimeter (1/8 inch) or with vegetation should be cleaned
and sealed prior to application of the FRS.
h. Application. After sufficient mixing the FRS mixture should be poured directly on the pavement
surface and squeegeed across the pavement surface. In hot weather conditions where the pavement
surface gets hot, the application of a fog spray of water prior to application of the FRS material would
assist in bonding the FRS to the pavement surface. A minimum of two applications of the FRS material
should be used to eliminate the possibility of any continuous, full-depth voids in the FRS. When
possible, each additional application should be made perpendicular to the previous one. Whenever
possible, consecutive lanes should be placed while the sealer mixture applied in the first lane is still
semifluid and workable. If operations preclude fresh working joints, the previously laid pass must be
allowed to set and cure sufficiently so it is not scarred, torn, or scraped from the pavement surface
during the placement of the adjoining pass.
i. Curing. FRS's cure by evaporation of the water from the sealed pavement surface. Sunlight and
warmer temperatures will increase the rate of curing. The time for curing can vary from 2 to 24 hours
depending on the thickness of FRS applied and the existing climatic conditions. FRS's should not be
applied when freezing temperatures (<0EC, <32EF) are possible within the curing time required.
5.
MICRO-SURFACING.
a. General. Micro-surfacing, also known as micro-texturing, macroseal, or macro-pavement, is a
latex-modified asphalt emulsion slurry paving system. This system was originally developed in West
Germany in the 1970's and has been used in the U.S. since 1980. The total system generally consists
of a latex-modified asphalt emulsion, chemical additives, high quality crushed aggregate and mineral
filler (usually Type 1 portland cement), and water.
b. Equipment. The methods of mixing and application are similar to those of a slurry seal. Other
equipment such as brooms, loaders, and asphalt distributors are the same as for a slurry seal. The
equipment required for mixing and application of microsurfacing mixtures are different than these
required for slurry seals. Mixing is accomplished in a multi-bladed twin-shaft pug-mill mixer. Application
equipment with constant agitation within the slurry box is required to achieve a uniform placement of
slurry. Micro-surfacing mixtures are placed with self-propelled mixing and placement vehicles. These
vehicles have bins and tanks to carry all the aggregate, filler, asphalt emulsion, water, and additives
required to make the mixture. There are two basic types of continuous vehicles with the capability to
keep placing with the help of nurse or resupply trucks, and units which place and then leave for
resupply. These vehicles have the ability to apply a fog spray of water to the pavement directly in front
of the spreader box. The spreader box will contain blades to continually agitate the slurry. On relatively
smooth surfaces the rear seal is rubber and acts as a strike-off (screed). On rough surfaces a steel
strike-off is normally used to form an intermediate leveling course with another slurry over it. Rut boxes
are used to fill ruts in individual traffic lanes. These boxes are V-shaped with the point of the V toward
the rear of the box. They have two shafts with multiple blades on each side of the V to continuously
agitate the slurry. The box is designed to push the larger aggregate to the center and is equipped with
two metal leveling plates and a rubber strike-off.
c. Material requirements.
(1) Emulsion. The binder used in micro-surfacing is a latex-modified asphalt emulsion. The
base asphalt emulsion used is normally a cationic slow setting emulsion with a hard base asphalt
(CSS-1H) as specified in ASTM D 2397. The latex polymer is combined with the asphalt cement during
the emulsifying process, typically at a rate of 3.0 percent by weight of residual material.
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