About Asphalt Calculator
What is Asphalt Made Of?
Asphalt, a crucial material in infrastructure, is essentially a blend of aggregates, binder, and filler. It’s commonly used for a variety of surfaces, from sidewalks and bike lanes to parking lots, railways, and even airport runways. The aggregates in asphalt can include sand, gravel, crushed rock, and even slags. In a more sustainable world, asphalt has adapted to incorporate waste materials and byproducts, such as construction and demolition debris, as part of its aggregate mix.
Interestingly, asphalt is soft and elastic when heated. However, it’s not the material’s mechanical strength that makes it useful, unless it's functioning as an adhesive. The primary use of asphalt
through various methods. For example, a hard surface can be formed by repeated applications of light oil "dust layer" treatments, adding granular aggregate to an asphalt coat, or by mixing asphalt with components from the road surface itself.
Asphalt binds together stone, sand, and gravel to form asphalt cement, which is then used for roads and highways. Beyond paving, asphalt also appears in products for waterproofing, sealing, and insulation. According to the National Asphalt Pavement Association, the US alone has around 3,500 asphalt factories, producing approximately 400 million tonnes of asphalt pavement annually, valued at over $30 billion.
Benefits of Hot Mix Asphalt
Hot mix asphalt offers a range of advantages compared to other paving materials. It’s highly resistant to common issues like insects, weeds, and water, making it a durable and long-lasting option. It’s also one of the most cost-effective choices, suitable for both commercial and residential projects. Unlike paving materials such as bricks or slabs, asphalt can easily conform to curves and corners, creating a tighter seal with kerbing and minimising gaps where water or debris could enter. Materials like bricks and slabs can shift or separate over time, but asphalt remains flexible and strong.
Hot mix asphalt is produced by heating the asphalt binder to high temperatures—typically between 150°C and 175°C. At this temperature, it becomes more flexible and pourable, allowing any moisture in the mix to evaporate. This process makes hot mix asphalt particularly water-resistant and durable. As it cools, it hardens and solidifies, making it ideal for road surfaces. Fortunately, in places like Perth, where the climate remains warm year-round, hot mix asphalt can be used continuously, whereas in colder climates, it’s restricted to the warmer months.
Types of Asphalt
There are several types of asphalt used for different purposes, each with its own characteristics:
Natural Asphalt
Natural asphalt comes in two forms: lake asphalt and rock asphalt. Lake asphalt, for instance, can be found in layers of fossilised material in places like Trinidad, buried as deep as 60 metres. It’s a bitumen-rich substance, containing around 30% water, with purity levels ranging from 40% to 70%.
Residual Asphalt
This type of asphalt is produced through the distillation of crude petroleum oil, mixed with a base, to create a round, solid material.
Mastic Asphalt
Mastic asphalt is made by combining liquid bitumen with limestone and other fine and coarse minerals. When it cools, it becomes a solid, elastic block that’s highly durable, water-resistant, and non-flammable. It’s used for both paving and waterproofing, with the blocks reheated on-site for application.
Asphalt Cement
A mixture of bitumen, asphalt, and flux oils, asphalt cement is commonly used to create bituminous pavements.
Cutback Asphalt
Cutback asphalt is a liquid mixture made by blending asphalt cement with a petroleum-based solvent. It reduces asphalt viscosity, making it suitable for lower temperatures. It’s often used in roofing repairs, bituminous coatings, and other specialised applications.
Asphalt Emulsion
This is a blend of small asphalt cement globules, suspended in water with a tiny percentage of emulsifying agent. It’s used in low-temperature applications like tack coatings, fog seals, and bituminous surface treatments.
Hot Mix, Warm Mix, and Cold Mix Asphalt – What’s the Difference?
Hot mix asphalt is commonly used for city roads and highways. It’s heated to high temperatures (up to 350°F) to increase its pliability and water resistance. Warm mix asphalt, on the other hand, is produced at lower temperatures, which means it cools more slowly but is easier to transport and better for the environment. Finally, cold mix asphalt is a user-friendly, cost-effective option, ideal for winter construction and pothole repairs, as it can be packaged in bags and applied directly in colder conditions.
Hot mix asphalt is spread and rolled on roads, interstates, and highways, while warm mix is particularly well-suited for tunnels or days with poor air quality. Cold mix asphalt is excellent for pothole and crack repairs, lasting longer than the surrounding pavement. Contractors also use cut-back asphalt for tack coats, fog seals, and surface stabilisation, while mastic asphalt is preferred for construction, waterproofing roofs, and underground storage.
Asphalt Beyond Roads
Asphalt isn't just used for roads and highways; its versatility extends to many industries. Architects use asphalt for building dams, reservoirs, playgrounds, and parks. Farmers use it to line the bases of retention ponds and cattle containment areas, and even for fish farming. Asphalt is also used to prevent soil erosion and flooding. In the automotive industry, manufacturers use it to protect car fenders and hoods from rust, and to reduce road noise.
How to Prepare Asphalt Paving and Surface
Before applying asphalt pavement, the surface must be prepared properly. This starts with spraying a thin layer of liquid asphalt binder using an asphalt distributor. This process strengthens the bond between the new surface and the underlying ground. Once the mix is ready and transported to the construction site, it’s spread out using an asphalt paver. Afterward, asphalt rollers compact the mixture to achieve a solid surface.
The quality of the final asphalt pavement depends on two factors: the quality of the mix and how well it's compacted. Proper rolling techniques are essential to ensure that the surface is as compact as possible, providing the best possible road surface for vehicles and pedestrians alike.
In conclusion, asphalt remains a fundamental material in modern infrastructure. From roads and highways to parks and playgrounds, its versatility, durability, and sustainability ensure its continued use across a wide range of applications. Whether you’re driving on a city street or walking on a playground path, there’s a good chance that asphalt is underfoot, playing a vital role in shaping the world around us.
