Understanding Asphalt Paving a Beguiner’s Guide
Asphalt driveways, parking lots and roads take a severe beating from motored vehicles from the day they are paved.
It’s not just the thousands or millions of vehicles that pound on them dain in and day out, but it’s also the elements. From summer heat to winter snow, sleet and rain an asphalt pavement is needed for vehicles to park and drive on while experiencing a smooth and comfortable ride, and maximizing fuel efficiency with the confidence that it will provide reliable friction for vihicle tires to stop a fast moving vehicle confidently in case of a last minute slamming of the breaks.
After more than a century of use, asphalt has become a proven solution to pave driveways, parking lots, and roads. Aside from asphalt, there are several alternatives for paving material such as gravel, clay and stone, and concrete. Each of these alternatives have individual benefits but none are as widely used as asphalt.
Asphalt is a combination of fillers, binder, and aggregate. Aggregate can be a number of different materials used alone or in combination which include crushed rock, slag, sand or gravel. The binder is then added to the aggregate to hold it together. The binder that is most commonly used in making asphalt is bitumen. Bitumen is the residue that is obtained from the distillation process of petroleum. It is thick and highly viscous. It is what gives asphalt it’s cohesive properties and dark color.
There are three kinds of asphalt that are generally used for paving.
- Hot Mix Asphalt. As the name implies, this mix is made under the hottest conditions – between 150 to 180 degrees. For best paving results, the product must be kept at this temperature when pouring. This can make some of the toughest conditions for the asphalt crew when working with it.
- Mild Mix Asphalt. Mild Mix is made between 130 to 150 degrees and is easier to work with. It can be poured faster without the need to have the asphalt cool. In most cases, it is a good option to use for road repairs that need the section that is being repaired and need to reopened quickly.
- Cold Mix Asphalt that is not heated or melted but rather compressed to achieve the same result. The kind of bitumen that is used also differs. The bitumen is granular and when compressed will liquefy and coat the aggregate. That allows it to achieve its cohesiveness.
When paving roads or parking lots, asphalt paving companies have several options for asphalt mix; they can either transport their asphalt from the plant or they can construct a mobile plant to prepare the asphalt and pour it on the job site. Which they choose depends on the size of the project and the time to completion.
Why is Asphalt Preferred
There are several practical reasons for choosing asphalt. Not least among them is the fact that compared to other paving materials, asphalt is the most economical. There are two parts to asphalt economics. The first is that the recovery cost to pave the roads can be extended over a longer period. That is because asphalt roads last longer than other materials. The second element of the cost is that the roads require less maintenance over a given period of time.
Aside from the cost, there is the quality of the ride. Asphalt can be laid to provide ride comfort. Unlike other materials, especially concrete, which can be loud the have high vibration energy, asphalt can be quiet and smooth. This has a direct impact on safety. The louder the noise and vibration, the quicker drivers get tired. The longer they stay vibrant, the safer they are. Better ride quality and safety have been proven to be on asphalt roads.
It is also preferred because repair times are quick. In the event there is an accident or a section of asphalt needs to be replaced or repaired, it can be done quickly before the next high-traffic cycle. This is because asphalt does not have a cure-time. Once it is laid, it can return to service immediately.
Asphalt Paving Benefits
There are significant benefits one can derive from choosing asphalt over other materials. From an environmental perspective, there is a major recycling advantage when asphalt. All asphalt that is recovered from a site can be returned to the mill and crushed before it is used again without any degradation of quality. There are other materials that have the ability to be recycled, but most do not. The ones that can, are expensive to return to service.
The resistance to damage is less because it does not require pavement or expansion joints. Expansion joints are the crevices that are built into concrete pavements to allow for the expansion of the slab. Under the heat of the day, these slabs expand and if there are no expansion joints the two adjacent slabs will collide. This collision will result in buckling that will render the road unsafe and reduce its usability. Asphalt does not have that problem and thus does not require expansion joints. This is one of the reasons that the ride quality is significant;y better.
Another benefit of using asphalt is that it is flexible and customizable. Its flexibility allows it to be paved in tight space, around bends and corners or inclines. Its customization comes from the ability to alter the formulation of the asphalt to suit the environment that it is deployed in. Depending on the environment – whether it is constantly wet, frozen, or has heavy traffic, the formulation of the asphalt can be adjusted to provide the best outcome.
Asphalt has lower flooding issues because asphalt is porous. Unlike other surfaces, asphalt will allow water to penetrate and sink beneath the road and eventually be drained so that the pavement is dry. The crevices that are a natural feature of asphalt are at the perfect intervals that allow water to move into the crevices and dry beneath or to the side of the road while allowing the dry peaks of the asphalt to make contact with the tire’s surface.
What makes asphalt superior in addition to all the benefits mentioned above is that can be transported to the construction site in a piecemeal fashion. Unlike the slabs that have to be carried and paved, asphalt can be poured in sequence after the necessary aggregates and fillers are laid and rolled.