A lot of thought and planning goes into creating an even, durable asphalt surface. Timing, temperature, and technique all work in concert to ensure the best possible results, and every step has an impact on the one after it. Here are six tips for creating smooth pavement that lasts:
Good asphalt starts long before the actual job does. From the design stages to procurement, each step requires attention to detail and a willingness to revise as needed.
Once it's time to start, you'll also want to inspect all of your equipment and ensure that it's been adequately maintained. If you're not completely sure whether a component will last for the length of the job, replace it. Check all of the fluids and gauges, and be prepared to take care of any components that come into contact with asphalt throughout the job. These will need a release agent applied to keep your machines operating at their best. Preheat your screed to keep the mat from dragging or sticking.
Once you've started, you have to keep an eye on your material. You need a consistent mass of material in front of the screed — nearly all material faults are a direct result of an inconsistent head of paving mix. If the level fluctuates, the paver won't be able to lay a smooth surface. If the head of material increases too much, the surface may develop waves. If it suddenly decreases, then the asphalt can develop flaws. Ideally, the mass of the paving mix will be consistent across the full width of the screed. Some newer models have sensors that manage the paving mix, but screed operators should still know how to monitor their machines to ensure the best results.
In addition to having a consistent head of material, you need to maintain a constant speed. Change your speed, and you impact your ability to lay down a smooth, uniform mat and keep your hopper of paving material adequately full.
Asphalt has a tough job. It needs to be able to cope with cold, wet weather, unpredictable loads, and heavy traffic. It can't do this if it isn't properly compacted. Compaction removes excess air and tiny gaps that will compromise the asphalt's performance over time.
Properly compacted asphalt comes from three things: The right temperature, mat thickness, and a good compactor rolling pattern. Compaction needs to happen while the asphalt is still hot, so it maintains enough fluidity to allow the paving mix to shift, fill voids, and release the trapped air. You should be able to predict how fast your mat is going to cool based on the materials and ambient weather conditions, and anticipate how long you have to work with it before it's too firm to compact.
The depth or thickness of the mat depends on its eventual purpose. The materials and mat thickness of a road surface are all chosen based on the conditions it's expected to face. A residential asphalt driveway, for example, may be 2-3" thick after compaction, while a heavy-duty parking lot will be thicker. As a rule, your mat should experience a roughly 20-25% compaction to its final thickness. If it's too thin, it may not be workable enough to compact properly. Too thick, and it may be too unstable to do so.
Consistent speed and head of material are important for ensuring road smoothness, but they aren't the only factors. A precise rolling pattern is a major contributor to the smoothness and durability of the finished surface. Since there's a narrow window of time where the mat is still hot enough to compact, you need to set your rolling pattern so you can efficiently complete it before the asphalt cools too much. This window might be as small as ten minutes, so use this time as efficiently as you can.
You need to cover as much surface area as you can in the shortest time possible, while simultaneously avoiding stopping the roller in the same place each time. Staggering your stops can help you avoid creating depressions and other imperfections. This will make sure that you're able to compact the whole surface before it hardens, and potentially leave you an opportunity to correct any problems that arise.
Asphalt paving is an art and a science. A lot of calculations and design considerations go into the planning stages of a good road or parking surface, but it also requires experience to know how different materials behave. These tips can help you ensure that you're able to lay down a smooth, high-quality asphalt surface, no matter whether you're paving a driveway, highway, or anything in between.