Advantages of Asphalt Paving

Asphalt Paving is an ideal solution for parking lots and roadways. Its multiple layers are designed to support heavy loads for years without requiring full reconstruction.

The first ingredient is aggregate (gravel, sand, or crushed stone) bound by bitumen—a dark, viscous substance made from petroleum byproducts. This is mixed at an asphalt plant.

Asphalt has long been a popular material for highways, roads, and parking lots. Its durability and longevity are dependent upon the proper mix, thickness, compaction, and asphalt materials used. However, the mix and thickness of an asphalt pavement can vary from project to project, and the paving contractor’s experience and expertise are also factors that determine how well your asphalt will last.

When laying asphalt, contractors begin by first grading the area. This slopes the soil toward grassy areas and keeps water from pooling on the surface of the new road or driveway. Once the grading is complete, workers put down a sub-base layer. This is the load bearing layer made from crushed stones. This is followed by a binder course which helps reduce rutting. A well-constructed binder course requires stability, good stone-on-stone contact, and stiff or modified binders.

Once the asphalt mixes are prepared, they are loaded into specialized trucks and transported to the construction site. The hot asphalt is mixed with other materials such as sand and crushed stone to create the final product. Throughout the mixing process, samples are taken and tested to ensure that the asphalt meets specifications and quality standards. If needed, adjustments can be made to ensure that the asphalt is suitable for a particular application.

Over time, long-term aging can occur in HMA pavements due to environmental loading and exposure, traffic loads, temperature variations, the freeze-thaw cycle, and asphalt ingredients. TFHRC researchers are planning a new approach to evaluating the long-term performance of asphalt binders by measuring the dynamic stability of an asphalt mixture using bending beam tests.

Flexibility

Asphalt flexibility refers to the ability of pavements to flex and adapt to traffic loads, weather conditions, and other external stressors. Flexibility allows asphalt surfaces to bend and deflect, rather than crack or break, which can prolong the lifespan of the pavement.

The flexible structure of an HMA pavement is composed of several layers that work together to absorb and spread the load generated by traffic. The surface course is the stiffest layer and contributes the most to the overall strength of the pavement, while the underlying base and subbase courses are less stiff and provide a number of other functions, including drainage and frost protection.

One of the most important functions of the base layer is to distribute the accumulated loads from vehicles over a wider area (compared to the surfacing section) and to prevent ingress of water into lower pavement layers, which would weaken them. The base layer can be comprised of either a high-quality unbound aggregate or a bitumen bound aggregate mixture. The latter type is often referred to as the “paving material” and can be made of hot or cold mix, with or without fiber reinforcement.

Cold mix asphalt mixtures are typically used as an overlay and have a short life span. However, they do have some advantages, such as a soft nature that resists damage and stays soft in cold temperatures. Additionally, they repel water and can be mixed with gravel to improve wet weather skid resistance.

Energy Efficiency

Asphalt pavements require 20% less energy to install than other paving materials. This translates to fewer carbon emissions and better fuel economy for cars on the road. In addition, asphalt’s ability to reduce friction means that less energy is used to push cars along the road. This helps to reduce vehicle maintenance costs and lower the need for oil changes.

The primary source of energy in asphalt production is natural gas. This energy is required to heat the mixture to high construction temperatures in the hot regeneration process. This type of asphalt is typically used to construct high traffic roadways and interstates. However, at TFHRC we are researching cold mix asphalt, which can be constructed at room temperature and does not require heating.

In the paving phase, most of the energy consumed is generated by the paver and rollers. During this stage, the paving material is compacted into a layer that can withstand traffic loads. This requires a significant amount of mechanical energy, but it is a very efficient process.

Once the base and binder courses are built, the surface course is then laid on top of the layers. This final surface provides strong load bearing qualities, which reduce rutting in the base and binder courses. In the long run, this results in a road that can last decades or more without requiring full reconstruction. Additionally, asphalt’s water drainage capabilities redirect water to grassy areas instead of accumulating on the road, which can cause heaves and require expensive road repair.

Noise Absorption

The acoustic properties of asphalt pavement make it a popular choice for road construction projects. Its porous structure reduces noise from tire rubbing and vibration, while its surface texture offers a smoother driving experience. Additionally, noise-reducing asphalt often uses eco-friendly materials, making it a great option for sustainable and green urban development initiatives.

The main ingredients of asphalt are aggregates (crushed stone, gravel, and sand) and bitumen, which binds the aggregate together. The aggregates are mixed with the bitumen in a hot-mix plant, and the mixture is then delivered to the project site for paving. To increase its acoustic performance, some contractors use additives in their mixes. These include calcium sulfate, which helps prevent cracking, and polycyclic aromatic hydrocarbon extenders (PAHE), which help improve durability and reduce surface friction.

Studies have shown that the acoustic properties of a road surface depend on its porosity, pore size, and morphology. A noise test can be conducted by placing a microphone in close proximity to the tire-pavement contact surface and measuring the vehicle sound pressure level at different speeds.

In addition to its acoustic benefits, noise-reducing asphalt also provides other advantages like improved water drainage, reduced spray in wet conditions, and enhanced visibility. However, these benefits are not guaranteed, and specialized asphalt needs to be tested before its use on high-speed roads. It’s important to understand these differences and choose the right type of asphalt based on location, traffic density, environmental considerations, and budget.

Water Drainage

Water drainage is a critical factor in asphalt construction. A pavement that is not properly drained will experience moisture accumulation which can cause structural damage and deterioration. Standing water can also cause unsafe driving conditions for both pedestrians and vehicles. Proper asphalt paving should include at least a 1% slope, so that any water that accumulates is quickly conveyed away from the surface. Regular maintenance is another important factor to consider when it comes to preventing asphalt damage from water.

During construction, asphalt is mixed with binder and aggregate to form the final product. This asphalt is then placed on the surface of a road and molded to create a smooth, even, safe surface for walking or driving.

Proper drainage is essential to the lifespan of any paved structure. Moisture in any of the HMA (Hybrid Mix Asphalt) structures can cause structural problems such as differential heaving (the roadway heaves up and down due to a buildup of moisture in the underlying soil).

One way to prevent this from happening is to install a permeable base layer. This layer is comprised of a porous aggregate, usually with a class-5 aggregate. It is designed to help the underlying subgrade and/or aggregate base layer drain more quickly than a traditional, dense-graded permeable base. To ensure proper functioning, a 12-18 inch thick layer of good quality sand is typically included to help promote drainability. Another option is to install a drain tile, also known as an underdrain, which is a channel built below the pavement. The drain tile consists of geofabric as a filter, round river gravel, and a perforated pipe connected to a catch basin or stormwater pipe.

Safety

Asphalt is a flammable material, and it must be kept away from sources of heat, flames, and sparks. Workers should also avoid smoking near the work area. Fire suppression systems are essential for preventing and controlling asphalt fires. Additionally, ventilation systems should be installed to minimize the build-up of potentially harmful fumes.

Long-term exposure to asphalt fumes may cause breathing and lung issues such as bronchitis. Contact with high-temperature liquid asphalt can cause severe skin burns. The proper PPE should be worn to protect the body from these hazards.

To minimize the risk of exposure, paving contractors should try to enclose asphalt mixing operations to reduce worker exposure. This can be accomplished by utilizing mechanical devices that stir the asphalt in an enclosed space. This will also help to prevent contaminating the asphalt with other substances. It is also a good idea to improve onsite ventilation and scheduling the mixing process when fewer workers are on site.

For workers who will be working with asphalt, protective equipment should include gloves that are thermally insulated to protect against burns. Safety glasses or a face shield should be worn to protect the eyes, and a respirator should be used for protection from fumes. Ensure that all workers are properly trained on the handling procedures for each type of asphalt mix. Also, a clearly visible set of warning signs and the SDS should be easily accessible so that employees are aware of the risks associated with working with asphalt.