Suggested Polymer
Modified Asphalt Emulsion Specifications
XXX.010 General
XXX.020 Materials
XXX.021 Asphalt Emulsion
XXX.022 SBR Latex Compound
XXX.030 Blending Procedures General
XXX.031 Blending Procedures for Field Production
XXX.032 Blending Procedures for Plant Production
XXX.010 General. This
work consists of blending aqueous latex compounds with asphalt emulsions
for use in the surface treatment of roads. Applications include chip seals,
slurry seals and tack coats.
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XXX.020 Materials. Unless
directed otherwise by the Engineer, the polymer modified asphalt emulsion
shall be composed of 97.0 + 0.3% residual asphalt solids and 3.0
+ 0.3% residual latex solids blended by weight.
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XXX.021 Asphalt Emulsion.
The asphalt
emulsion shall conform to ASTM standards for asphalt emulsions listed in
ASTM D977 for anionic asphalt emulsions and D2397 for cationic asphalt
emulsions.
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XXX.022 SBR Latex Compound.
The latex
compound shall be an unvulcanized virgin synthetic rubber in latex form.
It shall be specially compounded to obtain optimum dispersion in the asphalt
emulsion. The manufacturer of the latex compound shall furnish a written
certification containing the total solids content of the latex compound
being supplied for the project and actual test results of a typical sample
showing compliance with the requirements of these specifications. The latex
compound, when tested in accordance with the method of test on file with
the Engineer shall conform to the following:
Type
of latex
Styrene / Butadiene Ratio
Total Rubber Solids, % by
weight
Ash, % of total rubber solids
by weight
pH |
Anionic
24+1 / 76+1
65-70
3.5 Max
10 Min |
Cationic
24+1 / 76+1
60-65
3.5 Max
6 Max |
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XXX.030 Blending Procedures.
The latex
compound may be blended into the asphalt emulsion either in a bituminous
pressure distributor or in a colloid mill.
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XXX.031 Blending Procedures
for Field Production. Fill
the bituminous pressure distributor at least half full with the asphalt
emulsion at the temperature for the intended use as specified by the manufacturer
of the asphalt emulsion. Add the required amount of unheated latex compound
while the distributor pump is set and operating at maximum capacity on
“Recirculate”. Complete filling the distributor with the desired quantity
of the asphalt emulsion. Continue to recirculate for about 15 to 30 minutes,
raising the temperature up to that specified for using the asphalt emulsion.
It shall be noted that in some instances there may possibly be an incompatibility
of the emulsion systems of the asphalt emulsion and the latex compound.
Before mixing any asphalt emulsion with any latex compound, a small trial
blend shall be made at the temperatures to be actually used for the blended
materials to verify that the emulsion blend will not “break” while handling
at the required temperatures prior to application on the road. The heated
blend shall be used within twenty-four hours after blending or shall be
thoroughly remixed daily before use. Caution shall be taken when changing
from one bituminous emulsion to another to thoroughly clean the mixing
and hauling equipment. This shall be done by thoroughly draining the tank,
flushing with water, circulating approximately 20 gallons of fuel oil through
the pump and then flushing with water.
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XXX.032 Blending Procedures
for Plant Production. The
latex compound may be added to the water/soap tank prior to emulsification
of the asphalt cement or injected into the water/soap line of asphalt cement
line entering the colloid mill at the asphalt emulsion manufacturer's plant.
Adequate safety precautions shall be taken to prevent the latex from back
flowing into the asphalt cement storage tank
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IMPORTANT NOTICE TO THE
ENGINEER. The foregoing is for engineers only for the purpose of assisting
them in preparing job specifications. Suggested specifications are for
use under what may be termed “average conditions”. No single standard specifications,
however, will cover satisfactorily all variations in local conditions relevant
to individual jobs. Before adopting suggested specifications, the owner's
engineer should give particular consideration to any special problems and
make such changes as are necessary. Nothing contained herein shall be construed
as recommendations or inducements to practice any invention covered by
any patent without permission of the patent owner.
