Adhesion loss to the substrate is usually an important cause for the deterioration of the wearing surface. What is ChemCo’s solution to this problem?
Epoxy Asphalt concrete uses a bond coat of Epoxy Asphalt that is sprayed onto the deck with special equipment (provided by ChemCo Systems). This bond coat provides tensile pull-off bond strength to the corrosion protection coating on the steel deck of at least 2.5 MPa. Unlike thermoplastic material based bonds, the Epoxy Asphalt bondcoat maintains its high performance even when the deck reaches temperatures over 70 °C.
What are the key points to successful placement of epoxy asphalt concrete pavement?
What are the material requirements of the adhesion layer and waterproofing layer?
No waterproof membrane layer is required. The low void Epoxy Asphalt pavement and bond coat are impervious to water. The steel deck is initially protected from corrosion with inorganic zinc coating or a zinc rich paint coating.
What information have past projects shown about rutting resistance of Epoxy Asphalt?
Properly mixed and installed Epoxy Asphalt does not rut, even with overloads at 70°C. Only one Epoxy Asphalt pavement in the US has reported rutting. The rutting occurred because the Epoxy Asphalt binder content was too high ( at 7%). Marshall stability of Epoxy Asphalt pavements at 60° C is usually between 12,000 and 17,000 pounds. Marshall stability at 204° C is over 4,000 pounds (above the common value of ordinary asphalt at room temperatures).
What is the main cause of failures in epoxy asphalt concrete?
When properly designed and applied, Epoxy Asphalt has not failed. The few decks that have had the surfacing replaced exhibited fatigue cracking long after the design life of the pavement and after the pavement had been subjected to many years of truck traffic (fatigue cracks that occur after the design life of the pavement can be filled with a thermo-set polymer to extend the life of the surfacing). Insufficient compaction of the surfacing can result in a void content higher than the required 3% max. High void content can result in premature wear and/or fatigue cracking. An excessively high binder content can result in reduced stability and displacement under heavy loads. Early replacement of surfacing showing displacements can prevent progressive failure.
Can the life of an Epoxy Asphalt pavement on an orthotropic steel bridge deck be predicted?
Dynamic flexural load testing of a specimen plate that simulates the deck system has been very effective in predicting the suitability of the paving system. The test program takes into consideration the range of deck temperatures the deck will be exposed to, the magnitude and number of wheel loads (including and differentiating truck loads). The test is carefully designed to produce the same radius of curvature in the test specimen as will exist in the pavement over the longitudinal stiffeners on the actual bridge deck.
How do traffic volume and overload influence performance of Epoxy Asphalt?
A properly designed Epoxy Asphalt surfacing with excellent aggregates on a steel deck plate 16 mm or thicker should withstand about 15 to 25 million cycles of U. S. legal-limit wheel load without cracking. However, wheel overloads can significantly reduce fatigue life. One very heavily overloaded truck can cause a comparable loss in fatigue life to many legal trucks.
For new projects or existing deck rehabilitation, fatigue tests should be made with the mix design and actual aggregates that will be used in the pavement.
On the San Francisco Bay Bridge, each lane carries in excess of 1 million vehicles per year and the bridge has carried over 250 million vehicles since paving was completed in 1976.
Can Epoxy Asphalt be installed over conventional asphalt pavement?
Epoxy Asphalt can be placed on conventional asphalt. However, a sound base is required. Any deficiencies in the underlying asphalt pavement, such as cracks or instability will sooner or later reflect through the Epoxy Asphalt pavement.