Types of Bitumen in Road Construction: Specifications + Important Factors in Selection!

The types of bitumen in road construction include petroleum asphalt, natural bitumen, and tar-based bitumen. Each of these bitumen products plays a crucial role in the quality and durability of road projects because of their various properties. Bitumen is a sticky, waterproof material derived from petroleum products or natural resources. Due to its strong adhesive and high resistance, bitumen is a key component in asphalt paving and road surfacing. The selection of bitumen for road construction should be based on the project type, climate conditions, and technical requirements. In this article from Iran E-Trade, we examine the different types of bitumen suitable for road construction and the factors influencing the choice of the best bitumen.

Bitumen and its composition

Bitumen is a hydrocarbon material with a dark brown to black color. It consists of carbon, hydrogen, sulfur, oxygen, and nitrogen and is easily soluble in carbon disulfide and carbon tetrachloride. At ambient temperatures, bitumen is solid. But it becomes soft and liquid as the temperature increases.

Four types of compounds constitute the composition of bitumen: Naphthalene and polycyclic aromatic hydrocarbons, polar aromatics such as phenols, saturated hydrocarbons, and heterocyclic compounds. These substances can be derived from various sources and classified into different categories. Due to its adhesive properties, water resistance, and flexibility, bitumen has many uses in road construction and maintenance. In the following sections, we will explore the different types of bitumen in road construction.

Specifications and Characteristics of Bitumen in Road Construction

Types of bitumen in road construction should have the following characteristics:

• High softening point: for withstanding different temperatures
• Strong adhesion: Ensures a firm bond with aggregates
• Moisture resistance: Prevents water penetration
• Proper flexibility: Reduces cracking on road surfaces
• High durability: Maintains quality over time

Types of Bitumen in Road Construction

There are various types of bitumen in road construction, each of which has its specific properties and applications. The road construction industry mainly utilizes three types of bitumen: petroleum bitumen, natural bitumen, and tar-based bitumen. The following sections provide more details for each type.

1. Petroleum Bitumen

This bitumen is derived from crude oil refining and is one of the most common types of bitumen in road construction. Petroleum bitumen is typically solid or semi-solid and includes soluble bitumen, penetration-grade bitumen, and bitumen emulsion. Because of its high mechanical properties and adjustable characteristics, petroleum bitumen has many applications in different asphalt mixtures and protective coatings.

2. Natural Bitumen

Natural bitumen, also known as mineral bitumen, is a type of bitumen found in nature in underground reserves. Compared to petroleum bitumen, it has greater durability and longevity. Natural bitumen has good solubility in organic solutions, high purity, consistent characteristics, and a high molecular weight and nitrogen content.

Natural bitumen is one of the types of bitumen in road construction. Known for its high purity and greater durability, natural bitumen is suitable for projects that require high resistance. However, it also has uses in waterproofing, asphalt, paints and inks, chemical industries, casting, and other applications.

3. Tar-Based Bitumen

Another type of bitumen used in road construction is tar-based bitumen, which is similar to petroleum bitumen but differs in its resources. Tar-based bitumen has different chemical compositions and physical properties. Tar-based bitumen has three categories: β, α, and γ, and is produced through the distillation of coal or petroleum materials. This Is one of the types of bitumen in road construction which has high chemical resistance and anti-corrosive properties and has many applications in industrial and specialized coatings.

Uses of Different Types of Bitumen in Road Construction

As mentioned previously, there are various types of bitumen used in road construction. Bitumen is a common material for mixing with aggregates to produce asphalt, adhering to different pavement layers, waterproofing old or new asphalt, and many other purposes.

Pure bitumen has wide usage in the road construction industry for producing hot mix asphalt. However, the application of various types of bitumen in road construction, including soluble and emulsified bitumen, also includes the following:

• Production of cold mix asphalt
• Manufacturing sealing and protective asphalt
• Applying single or multi-layer asphalt
• Surface dressing of roads

Important Factors in Choosing Bitumen for Road Construction

One of the key factors in selecting types of bitumen in road construction is the climate conditions. The choice of bitumen should be based on the region’s temperature and humidity levels. Additionally, the volume of road traffic also influences the bitumen selection. In general, the heavier, denser, and more directed the traffic is, and the hotter and sunnier the region, the firmer the bitumen should be.

What is the Best Bitumen for Road Construction?

There are various types of bitumen in road construction, each with its unique features, capabilities, advantages, and disadvantages. Although bitumen used in road construction can be quite diverse, the best one is natural bitumen or Gilsonite. Some of the key features of Gilsonite for use in the road construction industry include the following:

• High content of asphaltenes and nitrogen
• High solubility in organic solvents
• Excellent water repellency and high gloss
• Melting point between 160 and 220°C with high resistance to temperature changes
• Resistance to acids and bases
• Non-toxic
• Lower mineral ash content compared to other mineral materials

However, Gilsonite is more expensive than other types of bitumen used in road construction and is more brittle. reference