Manufacture of asphalt is one of the most elaborate processes in the construction industry. In fact, it is like baking a cake where all the ingredients must be mixed in the right proportions. An asphalt plant can either be a batch plant or a drum plant. Batch plants manufacture asphalt concrete in batches which are used directly in construction sites. On the other hand, drum plants make asphalt continuously and store it in storage silos. An asphalt plant works by manufacturing the asphalt pavement material and delivering it to the sites. Here is a sneak peak of the whole process.
The manufacturing process of asphalt.
Manufacture of asphalt is the main business of an asphalt plan, and it is done in several steps. The first step is the mixing of sand, aggregate, and filler in the correct proportions. The different aggregates are metered accurately at the cold feed bins for delivery into the dryer. Bins are of different sizes and gradations and their gates are adjustable to control the amount of aggregates entering the plant. This further determines the mix gradation.
This mix is then heated at high temperatures in the dryer drum. Aggregates move either in the direction of hot air (parallel flow drum) or in the opposite direction (counter flow drum) as they are heated. They are mixed with asphalt cement as they are being heated. This cement is normally stored in tanks at about 3000 F or 3500 F awaiting delivery into the drum.
In the primary collector, dust particles are removed from the exhaust gases before entering the secondary collector, where fine particulate date is removed before exhaust gases are released into the atmosphere. There is an additive silo in some cases that is located next to the secondary collector. This silo is used to store special fillers, fines or additives that are added to the mixture to make different types and grades of asphalt.
The mix is then taken to the storage silos. Surge silos are insulated but unheated because the mix stored in them for a short period of time. Storage silos on the other hand are insulated, heated and air-tight since they hold the mixture for a long period of time. Trucks are loaded from the storage silos to transport the mix to the construction site.
The process is however not as simple as it seems. Typically, an asphalt plant is highly mechanized and uses state-of-the-art facilities in the manufacturing process. Computerized manufacturing systems are used to enhance the efficiency of the manufacturing process.
At the construction site, surface material is first removed from the surface to make it suitable for asphalt application. The surface is cleaned by a brooming machine. The distributor truck then spreads the tack coat and the asphalt pavement material is spread and compacted by rollers.
In summary, the asphalt paving industry has been very important in the construction of asphalt motorways, highways, airport running ways, streets, drive ways, parking areas, airport runways, footpaths and even cycle paths, among other structures. Asphalt plants manufacture asphalt concrete for use in the construction of these structures and deliver it directly to the construction sites or store it in heated form in storage silos for future use.