Epoxy Asphalt

Nanjing, China Project

Detailed Information

What is Epoxy Asphalt?

	Laying the levelling course

The two-component Epoxy Asphalt binder, when cured, becomes a two-phase epoxy polymer that contains an asphalt extender. The continuous phase is an acid cured epoxy and the discontinuous phase is a mixture of asphaltic materials. It is a thermoset polymer (it will not melt). This binder, combined with high quality standard asphalt paving aggregates, forms a tough polymer concrete called Epoxy Asphalt Concrete. A hot spray application of an Epoxy Asphalt bond (tack) coat precedes the laying of the Epoxy Asphalt Concrete.

Advantages

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.

Corrosion Protection

Epoxy Asphalt provides another layer of corrosion protection for the steel deck in addition to the primary corrosion protection coating because of its low void content of less than 3%. The voids that do exist are not interconnected. The result is an impervious pavement with extreme resistance to penetration of water and chloride ions.

Completed replacement deck plate. Over 800 of these panels were installed on the Golden Gate bridge over a period of two years.

Resistance to Rutting and Shoving

Because Epoxy Asphalt binder is a thermoset polymer (as opposed to a thermoplastic polymer such as conventional and rubber-modified asphalt), it provides excellent resistance to rutting and shoving even under high wheel loads in hot and cold climates.

Skid Resistance

Epoxy Asphalt pavements 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.

Oxidation Resistance

Epoxy Asphalt binders exhibit extremely low rates of oxidation and loss of resiliancy unlike standard and polymer modifed 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 OECD research studies seeking a long-lived pavement for busy roads conducted by the International Transport Forum. 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.

Delamination Resistance

Epoxy Asphalt pavements include a separate, high strength, temperature resistant (non melting) 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 158F (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.

Minimum Traffic Delays

	Epoxy Asphalt bond coat is sprayed onto the inorganic zinc-coated deck plates. The bond coat is about 0.03 inches (0.68mm) thick.

Epoxy Asphalt provides the absolute minimum delays for re-paving existing bridges under traffic. An Epoxy Asphalt pavement is ready for traffic in its partially cured state once it has cooled to ambient temperature. It develops full strength over two to four weeks depending on average daily temperatures.

Local Paving Crews

Local paving crews using conventional asphalt paving equipment install Epoxy Asphalt. ChemCo Systems engineers provide training and technical support during the project. ChemCo supplies the special blending equipment (meter-mix machine) for the two Epoxy Asphalt components. This special equipment is operated by local labor. There is no need to import specialized labor.

Applications

Epoxy Asphalt placements on orthotropic steel decks range from the San Mateo-Hayward bridge, paved in 1967, to the SuTong Bridge, which was completed in 2007 and many others [see last table]. The San Mateo-Hayward pavement is in excellent condition today after 39 years of service with minimal maintenance. Orthotropic decks using epoxy asphalt include bridges paved in Canada, Australia, and Brazil. Two bridges have been paved with Epoxy Asphalt and then, after 20 years of successful service, re-paved with the same material. Epoxy Asphalt has been successfully used in climates with winter temperatures below 0°F and summer deck temperatures reaching 170°F.

Installation

Epoxy Asphalt helps meet the challenge of replacing old concrete bridge decks with orthotropic steel decks while minimizing traffic interruption. Shop applied Epoxy Asphalt Chip Seal provides a durable skid resistant surfacing that protects each steel plate from wear and corrosion until all plates are in place and welded together. Epoxy Asphalt concrete provides the long term wearing surface when it is installed after all deck plates are in place. Both the Golden Gate Bridge and the Lions Gate Bridge used this system for their deck replacement projects.

	2nd Yangtze River Bridge, bridge deck side view

The concrete deck of the heavily traveled Golden Gate Bridge was replaced and paved with no daytime lane closures. Lane shutdown began at 8 PM, paving began at 10 PM and all lanes were opened at 5 AM the next morning. Throughout the night at least one lane was always open in each direction for traffic.

Epoxy Asphalt Concrete vs. Asphalt Concrete

Epoxy Asphalt Binder & Bond Coat (neat)

Epoxy Asphalt Concrete/Binder — Bond Strength

Fatigue Resistance

Properly designed Epoxy Asphalt Pavements for orthotropic steel bridge decks provide a durable surface that resists fatigue cracking in the pavement in the negative moment area above the longitudinal stiffeners. Additionally, the pavement, acting as one element in the compsite deck system, reduces deck deflection under load and thus increases the fatigue life of the steel deck plate itself.

Dynamic testing conducted in independent civil engineering laboratories have shown that Epoxy Asphalt pavements resist fatigue cracking over a wide range of conditions. The following table summarizes recent results.

Above test results from study conducted by Transportation College of Southeast University, Nanjing, China, 2000
1. Test specimen: 14 mm plate 100 mm wide, center point load from underside.
2. Test load: 5kN load @ 10 Hz frequency

Left: Fatigue test setup in dynamic testing machine for 18°C test. Right: Environmental chamber for fatigue tests at 0 and 60 °C.

History of Epoxy Asphalt Pavements

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