What Is The Prime Coat And Tack Coat Difference: Applications and Comparison!

The prime coat and tack coat difference is an important topic in road construction and asphalt production, as it directly impacts the quality and performance of road layers. The distinction between prime coat and tack coat relates to the type of materials used, their applications and purposes, the execution process, and their consumption rates. Prime coat, which can create adhesion between the underlying layers and asphalt, is mainly applied on roads with soil or non-asphalt foundation. In contrast, a tack coat can increase adhesion between two asphalt layers and usually contains bitumen with lower viscosity. These differences are due to the varying needs of projects and environmental conditions of each layer, and the proper selection of each coat plays a crucial role in the durability and final quality of the road surface. Therefore, in this article from IranETrade, we will discuss more about.

What is prime coat bitumen and what are its uses?

The first step for explaining the prime coat and tack coat difference is explaining each. Therefore, a prime coat is a thin layer of bitumen that can prepare the underlying road surfaces (such as its soil bed or base layer). This layer can improve the bond between the foundation and the upper layers of the pavement. The prime coat increases adhesion, reduces dust, and enhances resistance to water penetration.

Type of Bitumen Used In Prime Coats

For producing prime coats, road workers usually use bitumen emulsion or cutback bitumen. Common types include:

Bitumen Emulsion

A mixture of bitumen and water with chemical additives that manufacturers apply to it in liquid form. Because of its ease of use and reduced environmental hazards, it is a popular product.

Cutback Bitumen

The manufacturers dilute this bitumen with petroleum products (such as naphtha or kerosene) to increase its permeability and fluidity. Types of cutback bitumen include MC-30, RC-70, and RC-250. Therefore, the choice of cutback bitumen depends on the weather conditions and soil.

Amount of Bitumen Used Per Square Meter In The Prime Coat Method

One of the important prime coat and tack coat differences is their amount of use. For instance, the amount of bitumen used in the prime coat depends on the type of bitumen, the foundation conditions, and the project objectives. The typical consumption amount is as follows: (These values are adjusted based on soil type (permeable or compact), temperature, and moisture levels.)

• For bitumen emulsion: 0.7 to 1 litre per square meter.
• For cutback bitumen: 0.6 to 1.5 liters per square meter.

Ideal Temperature For Applying Penetration Grade Bitumen

Applying the prime coat is an essential step in road construction and foundation improvement because it plays a key role in enhancing the durability and quality of the road’s upper layers. The selection of bitumen type, the amount of its application, and temperature should be based on environmental conditions and soil types to achieve optimal performance.

The prime coat and tack coat difference is also in their temperature of use. The suitable temperature for using penetration-grade bitumen is a crucial factor in the proper application of the prime coat. This temperature depends on the type of bitumen:

• Bitumen emulsion: Applicable at ambient temperature (20 to 50°C).
• Cutback bitumen: Usually heated to 50–70°C to achieve the proper fluidity for soil penetration.
• Ambient and foundation temperature: The minimum ambient temperature should be above 10°C to ensure optimal bitumen performance.

What is Tack Coat?

Now that we have explained the prime coat and tack coat difference, let us see what a tack coat is. A tack coat is a thin layer of bitumen applied between different pavements and especially between asphalt layers. It can enhance adhesion and ensure proper bonding between layers and prevent their separation due to traffic and temperature. This method improves structural integrity and extends pavement lifespan.

Types of Bitumen Used For Tack Coat

The following types of bitumen are suitable for applying tack coat due to their technical properties and strong adhesion:

Bitumen Emulsion

Bitumen emulsion is the most common choice for a tack coat as it spreads easily and provides excellent adhesion. Its types include CSS-1, SS-1, RS-1, and CRS-1. Due to their water content, these products are safer and more environmentally friendly.

Cutback Bitumen

Cutback bitumen is usable in specific conditions and at low temperatures. Suitable types include MC-30 and RC-70.

Pure Bitumen

Using pure bitumen is generally less common, but you can use it in specific projects with prior heating.

Bitumen Consumption per Square Meter in Tack Coat Method

As we mentioned previously, the consumption rate of bitumen is a prime coat and tack coat difference. The amount of usable bitumen is determined based on its type, surface conditions, and project objectives. Common quantities for these bitumen are as follows:

• Bitumen Emulsion: 0.25 to 0.5 litres per square meter
• Cutback Bitumen: 0.2 to 0.4 liters per square meter
• Pure Bitumen: 0.15 to 0.3 litres per square meter (if used)

Application Temperature of Bitumen in Tack Coat Method

The temperature for applying tack coat bitumen varies based on the type of bitumen:

Bitumen Emulsion

For tack coat application, bitumen emulsion is usually applicable at ambient temperatures (minimum 10°C). If needed, it can be heated to 50–60°C.

Cutback Bitumen

For tack coat application, cutback bitumen is usable at a temperature of 50–70°C.

Pure Bitumen

Tack coat is a thin layer of low-viscosity bitumen used to enhance adhesion between two asphalt layers. This method is particularly effective in preventing layer separation and increasing the durability of asphalt structures.

Pure bitumen requires a higher temperature for tack coat application and is heated to 150–180°C.

The Difference Between Prime Coat and Tack Coat

The prime coat and tack coat difference is that prime coat and tack coat are two distinct methods of applying bitumen in road construction and maintenance. The main difference between a tack coat and a prime coat is that each process has a specific purpose. For example, these two methods differ in several aspects, such as the type of bitumen, consumption amount, application goals, and execution methods. We will discuss these differences further in this article from the Iran E-Trade blog.

1. Definition and Purpose of Use

A major point of prime coat and tack coat difference is their purpose of use. Prime Coat is a layer of bitumen with a high grade of penetration that is applicable to non-asphalt surfaces (such as gravel or aggregate). But tack coat is a thin layer of bitumen that road workers apply between two asphalt layers or between asphalt and a concrete surface. The purpose of using the prime coat is to strengthen the bond between the base and the asphalt layer, while the tack coat enhances adhesion between layers and prevents separation or slippage of pavement layers. The key characteristic of prime coat bitumen is its ability to penetrate surface pores and fill voids for deeper bonding. However, the main trait of tack coat is creating a sticky layer on the surface without requiring deep penetration.

2. Type of Bitumen Used in Prime Coat and Tack Coat

The type of bitumen used is another prime coat and tack coat difference. Prime coat primarily uses low-viscosity cutback bitumen such as MC-30 and, occasionally, diluted emulsions. However, in tack coat, bitumen emulsion like CSS-1 is commonly used, while cutback bitumen is rarely utilized in special cases.

3. Bitumen Consumption

Another prime coat and tack coat difference is in their consumption rate. For instance, prime coat application requires 1.0 to 1.5 litres per square meter, as it needs to penetrate the base layers. On the other hand, applying a tack coat uses 0.2 to 0.5 litres per square meter, focusing on surface adhesion.   reference Bitumen Price