Asphalt is the most common type of paved surface in the United States. It is used in roadways, parking lots, and driveways. Asphalt installation begins with the demolition and removal of the existing surface. Heavy machines haul away the old material and prepare the underlying gravel base.
Once the sub-base is laid and graded, it's rolled over with heavy machinery in a proof roll process. It ensures the underlying surface is strong enough to support the top layer of asphalt.
Sub-Base
Asphalt pavement is a composite material consisting of stone, sand, and additives – most importantly, it contains bitumen, making it black and sticky. This asphalt is poured, rolled, and compacted to create a smooth surface that is both durable and attractive. The most common asphalt is made from petroleum products, but there are also many alternative binders such as slag, fly ash, and treated swine manure (that's right – it's not just for cooking).
Before asphalt paving can begin, the old pavement must be removed, and any structures like wires or pipes must be adjusted to avoid damage during construction. Then the ground must be graded and sloped to promote water drainage. Once the base is in place, it's time for the binder and topping. The binding is applied to the aggregates and then heated. This heat softens the bitumen, which clings to the aggregates and holds them together. The top course is then rolled and compacted to create the jet-black asphalt we all know and love.
Binder & Surfacing
Asphalt is a durable, affordable, and sustainable paving solution. It is made of aggregates (crushed stone, sand, gravel, or recycled material) bound together by bitumen.
To make the asphalt mixtures that paving companies use, the ingredients are weighed at an asphalt plant with a belt-weighing instrument and then dried using a rotary dryer. The dried components are sifted and then stored in silos.
Once the base is ready, your paving contractor will do an inspection called a proof roll. This process checks for soft spots in the sub-base layer. The sub-base layer will be undercut and repaired if it is deemed soft.
Next, the binder and surface course are installed. The binder course is a thicker, heavier layer that provides the load-bearing capacity of the finished pavement. The surface course, the wearing course or blacktop, is lighter and uses a smaller aggregate than the binder course. It helps the surface look tighter and smoother while shedding water faster than the more porous binder course.
Paving
Before new asphalt can be laid, any existing concrete or pavement must be removed using large equipment like forklifts and bobcats. The material is then recycled and used in the new mixture to reduce waste as much as possible.
After the sub-base is installed and any soft spots are undercut and repaired, it's time to install the binder and surface course. The binder layer uses larger aggregate to create a strong and durable base, while the top surface is made of smaller particles to provide a fast and smooth ride.
Both layers are then rolled and compacted to ensure the asphalt has reached a specific density. Once this is achieved, the new road or parking lot can be driven on – carefully! The asphalt will take a little while to harden fully, though. It is an excellent opportunity to check that any traffic markers, speed bumps, or other structures have been installed as needed.
Sealcoating
Asphalt paving is only complete with the final step of seal coating. Professionals best conduct this preventive process regularly to preserve the life of your asphalt surfaces and minimize cracking.
After the sub-base is laid and soft spots identified and undercut, it's time to install the binder layer and surface course. That is the strength of any new asphalt surface and consists of large aggregate mixed with oil to produce jet-black pavement that provides a beautiful and durable surface.
When the binder and surface courses are installed, the entire paved area is compacted with multiple passes from compaction roller machines to ensure it's densely packed. It's also smoothed to ensure no small bumps of aggregate or stone are poking through the new surface. It is a vital part of the process and can dramatically improve the overall appearance of your asphalt surface. It also protects the asphalt from oxidation and the sun's UV rays, slowing down deterioration.