Pavement construction can vary widely depending on the local climatic conditions and traffic requirements. In general, most paved surfaces are made up of three layers: an asphalt or concrete base course, a wearing (surface) course; and, surface treatments such as seal coats. Each surface has its own design criteria that affect durability, safety, cost-effectiveness, and ride quality. To provide a basis for understanding the role of seal coatings in pavement management, it is necessary to know the equipment used in this process and their functions.
1) Belt-fed seal coating equipment
Belt-fed seal coating equipment has a large roller that is on the end of a long conveyor belt. The roller squeezes out the asphalt (bitumen) material through an opening which coats the road surface as it travels over the said road. Afterward, it collects in a storage tank until it exits the machine at a different opening and drops onto a landscaped area.
2) Spraying Seal Coating Equipment
Spraying seal coating equipment works much in the same way as a paint sprayer in that it has a storage tank for the sealant material. When in use, this type of machine pours out asphalt through an opening that coats the road surface before draining back into its collection tank. The thickness of said coat depends on how often operators must stop to refill said tanks with more material or "makeup" new mix if it has become too hard to spread out evenly after multiple passes over the same area.
3) Vacuum-assist seal coating equipment
Vacuum-assisted seal coating equipment uses the vacuum feature to pull both air and excess seal coating material back into its storage tank. Asphalt is poured out through an opening, covering the road surface, after which some of the excess seal coat drops back onto this same area due to said suction-assisted "drawing up." This type of equipment typically has a thicker roller than belt-feed or spraying models, producing a thicker coat in one pass rather than multiple passes. The trade-off with such equipment includes longer times for preheating and longer drying periods during which road users cannot use these roads.
4) Heated spray seal coating equipment
Heated spray seal coating equipment works in much the same way as spraying models but instead relies on an airless propulsion system which requires less material and makes it easier to cover large areas in a single pass. The drawback to this type of equipment is that the operator must fill the storage tank with hot seal coat material; otherwise, it becomes difficult to pump through the cold system. Also, such machines do not use vacuum assistance features or have heated rollers like their counterparts.
5) Cold-applied seal coating equipment
Cold applied seal coating equipment preheats asphalt until it reaches a state just before liquefaction (a gooey consistency). It then applies to the road surface in one or more coats depending on thickness requirements. It does not reach a point where asphalt actually begins melting and thus does not require preheating. This type of equipment is belt-fed. It typically has a roller that does not need to be as wide or thick as those typically seen on heated spray models, but it must cover large areas in only one pass from start to finish. However, the trade-off is that cold asphalt often takes longer to dry before road users can use said road surface.
All five types of seal coating equipment produce the same basic results: an even layer covering old coatings, cracks, and potholes while making new roads look more attractive with a freshly sealed surface. From there, decision-makers choose what works best for their own specific needs based on cost vs. time effectiveness and environmental sustainability.
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