Epoxy asphalt is asphalt mixture with epoxy modified bitumen as binder. Mostly, the epoxy modified bitumen is a two-component. It becomes a two-phase epoxy polymer that contains an asphalt extender after cured. The continuous phase is an acid cured epoxy and the discontinuous phase is a mixture of asphaltic materials. It is a thermosetting polymer. It will not melt when heated. This binder, mixed with high quality standard asphalt paving aggregates, forms a high quality polymer concrete called Epoxy Asphalt Concrete. Epoxy asphalt can be used for pavement design for many locations where requires special performances.
Epoxy asphalt is applied with conventional paving equipment. It was originally developed in the late 1950s by Shell Oil Company as a material designed to withstand the damage jet fuel could impart on pavement. In 1967, it was used to strengthen the surface of San Francisco Bay’s mile-long San Mateo–Hayward Bridge. After more than 40 years, the bridge’s surface is reportedly in excellent condition.
Advantages of epoxy asphalt
1. Fatigue Resistance: The excellent fatigue resistance of epoxy Asphalt enables it to maintain its integrity (on orthotropic steel bridge decks) without cracking even after the deflections caused by millions of wheel loads. The composite action of the epoxy asphalt, unlike that of more flexible pavements, increases the fatigue life of the steel deck and structure by reducing deflection, and thus strain, in the steel.
2. Corrosion Protection: Epoxy Asphalt provides another layer of corrosion protection (for the steel deck or asphalt pavement surface) because of its low void content. The voids that do exist are not interconnected. The result is an impervious pavement with extreme resistance to penetration of water and chloride ions.
3. Resistance to Rutting: Because Epoxy Asphalt binder is a thermosetting polymer (as opposed to a thermoplastic polymer such as conventional and rubber-modified asphalt), it provides excellent resistance to rutting even under high wheel loads in hot and cold climates.
4. Skid Resistance: Epoxy Asphalt pavements usually include high quality, polish resistant aggregates that provide outstanding skid resistance throughout their life. The Epoxy Asphalt binder does not “bleed” as do thermoplastic bituminous paving materials when the pavement gets hot. As soon as the binder on the aggregate exposed to traffic wears off, vehicle tires see only the aggregate.
5. Oxidation Resistance: Epoxy Asphalt binders exhibit extremely low rates of oxidation and loss of resiliency unlike standard and polymer modified binders. Pavements and overlays constructed with Epoxy Asphalt maintain their properties and do not become more rigid with time. These properties have been validated by several research studies. In addition, New Zealand is evaluating Epoxy Asphalt as a extended life binder for open-graded porous pavements, in an application where the binder is exposed to more air and water by design.
6. Delamination Resistance: Epoxy Asphalt pavements include a separate, high strength, temperature resistant (non melting at higher temperature) bond coat. Unlike regular or polymer modified asphalts, the Epoxy Asphalt bond coat provides a high strength bond to the underlying substrate (concrete or steel) even at elevated temperatures of 70C. In some cases, where delamination has been identified previously as a primary cause of failure, the Epoxy Asphalt bond coat has been successfully employed with polymer modified SMA pavements on steel decks.
7. Superior substrate adhesion: epoxy asphalt can provide high adhesion strength to hold the aggregate from vehicles. The adhesion between aggregates and at the interface between epoxy asphalt and asphalt mixture is much higher than traditional asphalt mixtures (2-4 times stronger than conventional asphalt mixture).
8. Minimum Traffic Delays: Epoxy Asphalt provides the absolute minimum delays for re-paving pavement surface under traffic. An Epoxy Asphalt pavement is ready for traffic in its partially cured state once it has cooled to ambient temperature (but may need one month to get fully cured). It develops full strength over two to four weeks depending on average daily temperatures.