asphalt emulsion manufacturers association

#Asphalt emulsion manufacturers association full

“Interfacial bonding is necessary to transmit traffic loads down through the whole pavement structure. “Tack coats are used to ensure a bond between the surface being paved and underlying course,” Mohammed said in November. In the paper co-authored by Mostafa Elseifi, Ph.D., and Ramendra Das, Mohammed spells out the whys of optimal bond coat placement and the problems of inadequate placements.

Mohammed, Ph.D., Louisiana Transportation Research Center of Louisiana State University, in his paper The Effect of Tack Coats on Asphalt Pavement Performance, presented at the International Symposium on Asphalt Emulsion Technology, Arlington, Virginia, Nov. Interlayer bonding is essential to optimize bituminous overlay performance, said Louay N.

#Asphalt emulsion manufacturers association full

The need for asphalt emulsion-based bond coats to be used consistently and placed full lane-width was emphasized in a technical presentation late in 2016. Tack is such a cheap component that it makes little sense to shortchange this critical step and introduce so much risk.” “Therefore, the risk of a poor or a compromised bond from not applying tack should be deemed too great when one considers the ramifications of the loss of fatigue life from this condition. “An analysis of bid tabs shows that the cost of tack coat is relatively minor compared to other components of a typical paving project,” consulting engineer Dale Decker said. If tack coats are not a contract pay item, their application may be at the mercy of the contractor, who might consider bond coats an additional expense. In its own way, at least one DOT doesn’t require them on milled surfaces. Some local road agencies don’t provide detailed bond coat specs. Shear strength is highest in top bituminous layer, suggesting need for firm bond between layers provided by properly executed asphalt emulsion bond coat Image courtesy Louisiana Transportation Research Center “Although we can design, construct and rehabilitate each layer independently, the layers must be bonded together for the pavement to respond to loads as intended,” NCAT said. Regardless of function, if the layers aren’t bonded together, the interface between layers becomes the weak link in the system, and the pavement will not perform as intended. “Intermediate layers can be designed to be highly crack-resistant if placed over an existing pavement with joints or cracks, or they can be designed as high-modulus layers to provide structural stiffness to the pavement to minimize tensile strains that lead to fatigue cracking, and limit high compressive strains that lead to permanent deformation in lower unbound layers.”

“Building asphalt pavements in layers provides a number of advantages, each layer can be engineered to have specific characteristics and properties,” the National Center for Asphalt Technology (NCAT) reported in Spring 2015.įor example, surface layers may be designed to provide high levels of friction, be porous to drain water and eliminate hydroplaning, and optimized to provide low levels of tire/pavement noise, NCAT said. Like plywood, asphalt pavements are built of layers, and their bonding is critical to good performance.

Thin veneers of wood are glued to each other to form a strong sheet of plywood. But if a strong bond is not created between the layer on which the asphalt driving course is placed, be it asphalt or concrete, the new asphalt surface is at risk of failure. Today, according to the Asphalt Pavement Alliance, some 94 percent of America’s roads are surfaced with asphalt.

Here we’ll talk about why you need to tack before paving.Īsphalt emulsion bond coats stop delamination and movement of conventional or thin asphalt overlays when they are placed over bituminous, Portland cement concrete or cold-milled pavements.Īlso called “tack” coats, bond coats adhere a fresh layer of asphalt to a lower layer of pavement. Asphalt emulsion bond coats glue layers of pavement together, give pavements durability by helping them resist shear forces.