Asphalt plants build the construction materials that build America including road construction. In this video we learn how asphalt is made in asphalt batch mix plants and in asphalt drum mix plants.
Asphalt is a mix of rocks (aggregate) and oil (bitumen-class hydrocarbon mixture some time referred to as asphalt binder). Amazingly, asphalt is one of the most recycled commercial materials in the United States. Ground up asphalt pavement can be added back into the mix of newly produced asphalt. Asphalt is just about everywhere but most people don't know much about it. It is used to build roads, parking lots, airport runways, sidewalks, tennis courts, playgrounds and bike paths.
This video is about Hot Mix Asphalt. Its called hot-mix because not only is it mixed hot, it must remain hot for the paving and compaction for repair or installation. The need for the asphalt to remain warm while paving and compaction is performed is one of the reasons so much paving is done during the summer and asphalt plants are near where the construction is performed. Also, the heavy weight of asphalt makes local delivery less expensive.
Asphalt Batch Mix Plant Production Process
Step 1 – Cold Feed Bins
Aggregate cold feed bins hold the necessary aggregates to produce asphalt. At this point the aggregates are cold and wet. Then, aggregates are conveyed to the dryer.
Step 2 – Drying Aggregate at 200 - 350 degrees Fahrenheit
The drying process is designed for three purposes:
To take moisture away from the aggregates.
To heat up the aggregates. This is important when all the ingredients are put together as the high temperature will give workability to the mix.
Take very fine aggregate through the air and reuse it as filler in the final mix.
Step 3 – Hot Elevator
After the aggregates are heated up, they are transported through an elevator. It also helps to transfer the heat throughout the aggregate.
Step 4 – Screening
At the top of the plant, the aggregate is divided by size. Each screen has holes of different sizes, allowing the aggregate to filter properly. The rocks that are too big are sent down through the right side elevator.
Step 5 – Mixer
The aggregate has been divided in four sizes. The sizes of aggregate used in the mix will depend on the type of asphalt to be prepared. Recycled Asphalt is conveyed into the mixer too. Bitumen is added to the mix from the tanks. Reclaimed Filler from the dryer is used instead of new filler when possible. (Allowing the discharge of dust-free, clean air into the atmosphere). Almost 95 % of the asphalt mixture is aggregate & its dust and 5 % is bitumen oil and recycled asphalt
Step 6 – Transport to Site or Hot Storage
The asphalt is now ready to be transported to the working site or hot storage.
Asphalt Drum Plant Production Process
Rock aggregate sorting is done prior to heating. Drum plants combine the dryer and mixing tower into a single drum that dries the aggregate, heats it to mixing temperature, adds the heated asphalt cement and dust, mixes it with the aggregate, then deposits the finished product onto a conveyor that takes it to the storage silo. And it does all of that continuously making it ideal for large projects that require the same asphalt mix recipe.
Getting the Right Asphalt Mix - Quality Control
Completed asphalt is evaluated for its quality in terms of consistency or viscosity, and purity as well as compaction.
There is also something called cold mix asphalt that is prepared differently and is normally used on small projects
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