To do this, the maltenes must disperse into the existing hard binder. This process is diffusion controlled and depends on the temperature, the viscosity of the binder and the viscosity of the oil. Emulsification makes very fine oil particles, allowing optimum penetration into the aged binder.
A rejuvenation seal is a form of chip seal. It's done by application of a specially formulated product that acts as both the binder and the rejuvenation medium. The product is an asphalt emulsion based on a grade of asphalt chosen for the climatic conditions (soft for cold climates, harder for hotter places). This emulsion contains the rejuvenation oil. This has two effects. The first is to make sure the rejuvenation oil is evenly distributed, and the second is to take advantage of the many benefits of emulsion binders in terms of adhesion and safety.
The emulsion is able to coat the surface evenly, penetrate, and rejuvenate. The binder will then hold a chip rock.
The emulsion also contains polymer modification. This ensures that the oil presence does not decrease viscosity too far and cause flushing problems. The following case study refers to Styraflex ERA, a product of VSS Emultech California.
Eldorado County, CA 2004
Eldorado county stretches from the foothills of the mountains above the Sacramento Valley through rugged mountains to Lake Tahoe. The "Golden County" of California has diverse terrain and climatic conditions. Eldorado county is a progressive county and its engineers are always ready to try new products.
The job consisted of several locations throughout the county. The product used was Styraflex ERA, a high binder rejuvenating emulsion with polymer modification.
The road surfaces were distressed by age cracking and raveling, and in normal circumstances would have been resurfaced or overlaid with hotmix. Styraflex ERA represented the most economic method of resurfacing and rejuvenating to prevent reflection cracking, and was capable of giving five to eight years of life before resurfacing may be necessary again.
Styraflex ERA was applied using a computer controlled and calibrated spray distributor truck at 0.35 to 0.45 gpm. An experienced onsite supervisor refined this application rate. Higher application rates were needed for higher levels of aging.
Weather conditions were fine and warm, and the Styraflex ERA generally penetrated about 1/16 to 1/8 of an inch. The aggregate, a 1/4-inch black volcanic rock, was spread by a computer controlled chip spreader. This allowed a high contrast and hardwearing seal to be formed.
Rejuvenation seals are a method of extending road service life. They are one of a tool kit of pavement preservation and maintenance methods that include slurry surfacing, chip seals and overlays. Used at the right place, Styraflex ERA is an effective tool.