Using Polymer Modified Asphalt Emulsions in Surface Treatments A ...

into the emulsion. High boiling point petroleum-based solvents that are high in aliphatic
content are generally preferred because they promote swelling and softening of the
rubber which improves particle wetting and increases adhesion (21), while also meeting
U.S. Environmental Protection Agency (EPA) emissions requirements. “RG-1”
represents a mixture of 40-50% CRM dispersed in a petroleum-based solvent, which is
post-added to the emulsion through simple mixing. RG-1 modifiers exhibit good stability
when blended with either cationic or anionic asphalt emulsions (21), with typical
treatment applications including chip seals and slurry surfacing.
Laboratory and short-term field testing of RG-1 modified asphalt emulsions indicate
improved crack and rut resistance, higher viscosity, lower thermal susceptibility, better
stone retention, and improved elasticity when compared to unmodified asphalt
emulsions, though results are generally less impressive than conventional forms of
polymer modification (21). In addition, some research shows that the use of RG-1
does not adversely impact setting times for slurries or microsurfacings (21). When used
in chip seals, RG-1 costs are approximately 2 to 5 cents per square foot, and for slurry
or microsurfacing the cost is about 1.5 to 3 cents per square foot (21). No special
equipment is required to add RG-1, and standard batch plant transfer pumps are
adequate for the task.
Another use of reclaimed rubber and emulsions involves the direct addition of 15-22%
of CRM to the hot asphalt binder used in some chip seals. In such instances, the
modified binder is sprayed on top of the pavement surface followed by an overlay of
stone, and then rolled. A fog seal of asphalt emulsion (generally, a 1:1 dilution) may
then be applied over the top of the chip seal to improve stone retention (23), although
this particular type of application does not constitute a direct form of polymer
modification of the emulsion per se. Cape seals may be constructed using CRM in a
similar fashion, by modifying the chip seal binder coat prior to the application of the
overlying microsurfacing or slurry seal.
21