Adhesive coatings are used in pavement construction to bond layers of asphalt together on roads. It is an emulsion of asphalt binder, water, and emulsifying chemicals. The coating must cover 90% of the road surface to prevent degradation effects. The thickness and volume of material required have been quantified since 2001. Bonded liner is also used to seal layers of precast concrete together. A preventive primer is sometimes used to reduce dust on the surface. In some countries, a cutback layer is applied instead of true tack coating.
An adhesive coating is essentially a type of industrial glue that is used in the pavement construction industry to bond layers of asphalt together on roads. It is an emulsion which is a liquid-liquid mixture of asphalt binder, water, and emulsifying chemicals that work to mix the ingredients together in a colloidal suspension. This asphalt emulsion is applied in a thin layer between layers of hot asphalt (HMA) when a road surface is being built and serves to create an adhesive bond between them. The coating must cover 90% or more of the road surface to prevent slippage, and if incomplete coverage is done, the roadway will be more prone to long-term degradation effects such as crocodile cracks, ruts and potholes.
The main ingredient in adhesive coatings is a bituminous liquid which is a liquefied hydrocarbon version of the solid asphalt surface itself. The emulsion may also contain a water dilution, which is common in some US applications of the product and serves to provide a more uniform application to the road surface. In European countries, a faster setting type of tack coat is used which does not require the evaporation of water from the emulsion, but still has a low viscosity or thickness. In some cases, an adhesive coating is also used that contains a liquid polymer base that acts as a binder in the latex. These variations create surfacing materials that can range from slow to fast setting and low to high viscosity depending on the demands of the road surface being worked on and the local climate.
The thickness of the tack coat layer applied and the volume of material required to perform an adequate job have been precisely quantified since 2001 based on the type of road surface being worked on. When the road surface is new construction of HMA, 0.03 to 0.04 gallons per square meter (0.14 to 0.18 liters per square meter) is required. These levels increase slightly if the surface is oxidized HMA and nearly double for milled HMA at 0.06 to 0.08 gallons/yd2 (0.27 to 0.36 liters/m2).
Bonded liner is also used to seal layers of precast concrete (PCC) together. Where milled PCC layers require the same amount of adhesive coating as milled HMA, plain PCC requires the same amount of material as oxidized HMA. The amount of tack coating also increases significantly if it is diluted in advance with water to promote complete diffusion on the road surface, with the volume of material used three to four times the volume of normal asphalt binder needed.
Some cases of liquid asphalt application also require the use of a preventive primer, which can reduce dust on the surface. If the road surface is not cleaned of dust when the coating is applied, it will bond to the dust instead of the top and bottom layers of asphalt, which leads to the failure of its adhesive properties known as delamination. In some countries, a cutback layer is applied instead of true tack coating, which is a mixture of asphalt that has been dissolved in hydrocarbon-acting solvents such as kerosene, and is then applied between layers of asphalt to bond them together.
Protect your devices with Threat Protection by NordVPN
