One essential component used in the building of roads and numerous other infrastructure projects is asphalt concrete. It is prized for being strong, adaptable, and reasonably priced. Knowing what makes it up can help us understand why it is so popular and how well it functions in different situations.
Bitumen and aggregates are the two main ingredients that make up asphalt concrete. Sand, gravel, and crushed stone are combined to create aggregates. These substances offer the required stability and strength. Bitumen, a black, viscous liquid or semi-solid petroleum product, is what binds the aggregates together. It is sticky and black.
These components work together to produce a robust, flexible pavement that is resistant to both severe weather and high traffic. The performance and longevity of the asphalt concrete may be impacted by variations in the proportion of each component based on the particular requirements of the project.
To improve specific qualities of the asphalt concrete, additional additives can be added in addition to the basic ingredients. For example, anti-stripping agents can increase the material’s resistance to water damage, while polymers can improve flexibility. These adjustments make it easier to modify asphalt concrete to fit the unique requirements and difficulties of various building projects.
| Component | Description |
| Aggregates | Crushed stone, gravel, or sand that forms the bulk of the mix |
| Binder | Bitumen that holds the aggregates together |
| Fillers | Fine materials like stone dust to fill gaps between aggregates |
| Modifiers | Materials like polymers to enhance performance |
| Water | Small amounts to help in mixing and compaction |
Often referred to as asphalt, asphalt concrete is a strong and adaptable substance that is used to pave parking lots, driveways, and roadways. It is mostly made up of a mixture of aggregates, such as crushed stone, sand, and gravel, held together by asphalt, a petroleum-based sticky, black liquid with a high viscosity. This combination produces a robust, adaptable surface that can withstand high traffic and a range of weather conditions, which makes it a crucial part of contemporary infrastructure.
- Properties and types of asphalt concrete
- Characteristics and properties
- Materials
- Gravel or crushed stone
- Sand
- Bitumen
- Road surface structure
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Properties and types of asphalt concrete
The elements of the asphalt concrete mixture are determined by the qualities and intended use of the coating. They then start developing each "ingredient" in percentage terms in order to get the materials needed for a particular road. Furthermore, the coating’s physical and chemical characteristics determine how it should be used. They are collectively referred to as "brand."
What is contained in the written work? Crushed stone, sand, and minerals are combined to make asphalt concrete. For viscosity and shape retention, bismuth is added.
Characteristics and properties
The functionality of the asphalt concrete mixture is dependent on the recipe and ratio of materials required. These are the following:
- laying feature;
- granularity (the grain composition is denser, therefore it can withstand greater loads);
- porosity (after laying, small voids remain in the rolled mixture – this phenomenon is called residual voids);
- crushed stone content;
- brand.
Asphalt concrete mixtures differ in their recipes even though their component compositions are similar.
Materials
According to the ways in which they are laid, asphalt concrete mixtures are divided into 5 categories:
"Warm." What makes it up? The foundation of the mixture is mineral filler. This has a very low viscosity percentage. The mixture is poured while still heated.
It will not compact the asphalt if the temperature falls below average. As a result, concrete pavers use specialized thermometers to continuously monitor the temperature.
Hot mixture has the greatest range of applications and is laid at a temperature above 100º.
"Warm." This type of asphalt is created by foaming and whipping bitumen. The mixture is exactly the same as when it was hot. It is already ready to be laid at a temperature between +70 and +80º. It is therefore simpler to work with.
"Cold." It is created by adding liquid bitumen to crushed stone or sand as a base. The powder does not need to be heated continuously and its temperature checked when it is laid.
It is possible to lay cold asphalt in the winter, even at -15°C. Simultaneously, this material is of a lower quality than the preceding two. Pothole repair is its primary application.
"Cast." In this mixture, "bitumen + mineral powder" is the primary ingredient. The mixture contains a very small amount of crushed stone. However, the material must be heated to between +190 and +250ºΡ before laying.
Workers that handle concrete thus get a liquid and extremely hot mass. It covers the surface where it was poured, spreading itself out.
When hardening, the coating is cast, waterproof and monolithic. The only drawback is the cost of production and laying of the composition. For this reason, the scope of application of cast asphalt concrete and its manufacture is limited.
"Cheese with asphalt." Chips are made by removing and crushing old asphalt surfaces. After that, they are restocked and packaged in bags.
Private home owners gladly purchase this coating for themselves because it is significantly less expensive. It is heated to lay such a powdery mixture.
Gravel or crushed stone
The following is the makeup of asphalt concrete. The two primary additives for road surfaces are crushed stone and gravel. They offer durability and strength.
The surface will not be strong enough for trucks and other large vehicles to drive over if there is not enough crushed stone added to the mixture. Under the wheels, it will quickly start to sag and crumble.
Sand
Sand is added to the asphalt concrete mixture to make it more environmentally friendly. Additionally, it shields pedestrians’ lungs from petroleum products.
Sand is a major component of asphalt used on pedestrian walkways. It is more convenient to walk on the surface because of this material.
Another use for sand is as a fine filler. Larger minerals are filled with its tiny particles (crushed stone).
Bitumen
The primary "shining" element in asphalt is bitumen. It’s made from oil, which has a lot of liquid resins in it. Oil clots were used in building even in antiquity.
Nitrogen and carbon are elements found in bitumen. This material is extracted from mines.
Gasoline and kerosene are extracted from the composition following fractional processing. The foundation for bitumen material will be obtained from the heavy residues.
Insufficient viscosity is one of the causes of low-quality asphalt. The degree of plasticity of the bitumen determines the quantity of oily materials in its composition.
This indicator is based on how well bitumen that has been extracted from oil stretches. Naturally occurring bitumen is another. It is not common. Usually, the material permeates rocks with pores. It is extracted from these rocks by melting it in a liquid solvent or by evaporating it in boilers.
Road surface structure
What will be used as the asphalt recipe is the design. Stated differently, what is the material ratio? Technical requirements and standards will be established based on their quantity.
In the modern world, where curves are used to construct the grain structure and mineral part, calculations are done using linear graphs.
The person in charge of the recipe for asphalt concrete verifies that:
- the mineral part is dense enough;
- the grain part corresponds to the permissible amount;
- and the minimum amount of bitumen – asphalt concrete of the required grade.
When it comes to creating long-lasting roads, highways, and pavements, asphalt concrete is a versatile and indispensable material in contemporary construction. Aggregates, binder, and fillers are some of the components that give it strength and flexibility.
The majority of asphalt concrete is composed of aggregates, which include sand, gravel, and crushed stone. They offer resilience to deterioration and structural integrity. As a kind of glue, the binder—typically bitumen—keeps the aggregates together and gives the mixture its cohesive qualities.
By filling the spaces between the larger aggregates, fillers like fine sand or stone dust improve the density and stability of the asphalt concrete. This mix of materials creates a surface that is strong and resilient enough to withstand heavy use and a range of weather conditions.
It is easier to recognize asphalt concrete’s importance in construction when one is aware of its constituent parts. Engineers guarantee the longevity and performance of roads and pavements by carefully choosing the proper mixture of materials, which improves and secures our everyday commutes.
