Since ancient times, the black cementing material known as asphalt has been used to construct roadways. Although there are natural reserves of asphalt, often known as rock asphalt, the industry that refines oil produces the vast bulk of asphalt used today. During the distillation step of refining, asphalt can be removed from the majority of petroleum types. Then the refined asphalt is turned into a mixture with different components. Bitumen is a form of hydrocarbon that is soluble in carbon disulfate; because of this quality, asphalt, which contains bitumen, is known as a bituminous substance. Bitumen is also contained in the tar that is formed by the destructive distillation of soft coal. This category includes both petroleum asphalt and coal tar, which are both bituminous compounds. Due to the major differences in their qualities, coal tar and petroleum asphalt should not be confused with one another. In contrast to petroleum asphalt, which is virtually entirely composed of bitumen, coal tar contains a somewhat higher amount of bitumen. Both of these components should be treated as separate entities. As a material for use in engineering construction and maintenance, asphalt's adaptability is one of its defining characteristics and benefits. At room temperature, asphalt is only semi-solid, but it is possible to transform it into a liquid by adding heat, dissolving it in solvents, or emulsifying it. As asphalt is a durable, easily-sticky cement that is also exceedingly waterproof and durable, it is ideally suited for use in the construction of roadways. 
In addition, it is very resistant to the corrosive effects of the vast majority of acids, alkalis, and salts. Asphalt concrete is utilized to construct more than ninety percent of all paved roads in the United States. It surpasses all other materials in terms of versatility, durability, and ease of installation. Asphalt is mixed with aggregates in order to form a consistent material for paving. Sand, gravel, crushed stone, slag, and rock dust are all examples of aggregates, which are sometimes known as mineral aggregates. Aggregates are hard, inert materials. In order to create pavements, aggregates are combined with asphalt, a cementing media, after being carefully chosen and graded. In an asphalt concrete pavement, the aggregates are the primary components that support the load of the vehicle. They make up around 90–95 percent of the combination based on weight, and approximately 75–85 percent based on volume. Aggregates used in asphalt concrete paving are divided into different categories based on their source or method of preparation. After this, a succinct explanation of the categories will be presented.
- Pit or Bank-Run Aggregates
Sand and gravel are two types of natural aggregates that are often extracted from pits or bank runs. Prior to being utilized for the purpose of asphalt concrete paving, they are typically screened to the appropriate size and washed to remove any debris. 
- processed aggregates
A natural pit or bank-run aggregate is considered to be a processed aggregate after it has been subjected to crushing and screening in order to make it appropriate for use in asphalt concrete pavements. Crushing often results in an improvement to the particle form by producing angular particles from rounded particles. The size distribution and range are both improved as a result of crushing. Additionally classified as a processed aggregate is broken stone. When bits of bedrock and huge stones are crushed to the point where all of the particle faces are cracked, it results in the formation of this material. Screening is a technique that is used to produce particles of varying sizes. Crusher runs are a type of aggregate that have gone through very little to no screening at all. These aggregates are often more cost-effective than screened aggregates and can be utilized in the construction of asphalt concrete pavements in a variety of settings. The rock dust that is created during the crushing of limestone is separated from the other crushed aggregate so that it can be utilized either as crushed sand or as a mineral filler in asphalt concrete pavements.
- Synthetic Aggregates
Synthetic or artificial aggregates are those that are generated by modifying the source material's physical and chemical properties. These aggregates are called "aggregates." Some are manufactured and processed particularly for use as aggregates, while others are the waste of production and a final burning process. Both types of aggregates are used in the construction industry. An example of a synthetic aggregate is the slag left behind from blast furnaces. Aggregate Materials' Favorable Characteristics When constructing an asphalt concrete pavement, the choice of aggregate material to be used in the pavement is determined not only by the availability, cost, and quality of the aggregate but also by the type of construction for which it is designed. Evaluating an aggregate material in terms of the following attributes will allow you to assess whether or not it is suitable for use in the creation of asphalt: 
- Size and classification system. The smallest sieve that an aggregate will pass through entirely unimpeded is considered to be the aggregate's maximum allowable size. Not only the largest size aggregate that can be used but also the gradation that is required is determined by how the asphalt concrete is going to be employed (distribution of sizes smaller than the maximum).
- Cleanliness. Certain materials cannot be used in the production of paving mixtures because they include foreign elements or substances that are harmful.
- Toughness. The ability of the aggregate to withstand crushing or disintegration while being mixed, placed, or compacted, as well as under the weight of passing traffic, is referred to as its toughness or hardness.
- Soundness. Soundness is the aggregate's ability to withstand deterioration induced by natural forces such as the weather, and it is quite comparable to toughness.
- The form of the particle. The aggregate particles' various forms have an effect on the overall strength and workability of the asphalt mixture, as well as the density that may be reached through compaction. When compressed, particles with an irregular shape, such as crushed stone, have a tendency to "lock" together and resist being moved.
- Surface texture. Surface texture has an effect on both the workability and the strength of the pavement. When compared to a smooth texture, the strength of something with a sandpapery or rough texture is significantly greater. Even though smooth-faced aggregates are simple to cover with a layer of asphalt, in general, their performance is not as good as that of aggregates with uneven surfaces. When applied on a smooth surface, asphalt has a more difficult time "gripping" the ground.
- Absorption. The ability of an aggregate to absorb asphalt and form a link between the particle and the asphalt is made possible by the porosity of the aggregate. Although some degree of porosity is required, extremely absorbent aggregates are typically not employed because of this preference.
- Stripping. The term "stripping" refers to the process in which the asphalt film becomes dislodged from the aggregate as a result of the action of water. Aggregates that have been coated with an excessive amount of dust can also create poor bonding, which results in stripping. Aggregates readily susceptible to stripping action usually are not suitable for asphalt paving mixes unless an anti-stripping agent is used.
There are also various forms of cold mix asphalt concrete, including aggregate base treated with bitumen. This may involve processing gravels, crushed stones, or combinations of gravel, sand, and crushed stone, each of which is stabilized with a predetermined percentage of asphalt. These combinations are frequently employed as a base course and to stabilize the surface of stabilized shoulders, while other functions may be provided by specific designs. In every design, a surface course or seal coat should be included to defend against the abrasive effects of traffic and the elements. Our sales executives are ready to answer any of your inquiries regarding bitumen purchases. You can contact them and they will reply as soon as possible.