Bitumen Emulsion is a liquefied type of bitumen with a low viscosity. By dispersing bitumen in water and adding an emulsifier, ordinary bitumen turns into a low viscosity liquid that can easily be used in a variety of applications, including repairing and maintaining roads, waterproofing, spraying, etc.
Emulsions make it easy to handle, store, transport, and apply bitumen at a lower temperature: Since this type of bitumen is liquid, there is no need to heat it before application. Moreover, applying bitumen emulsions using cold techniques reduces the consumption of energy and makes road construction environmentally friendlier.
What is Bitumen Emulsion Composition?
It is a combination of water and bitumen. As the mixture of water and oily products quickly separate, a third component is normally added to the mixture, in order to make it more stable. Known as emulsifier, this third component is used for making a mixture of water and oil dispersed in each other. In addition to their ability to reduce the tension between oil and water molecules, emulsifiers have an electronic charge that affect the molecules of bitumen emulsion and lead to the categorization of it into Cationic and Anionic.
Cationic emulsifiers, for example, form a layer of positive charge around the bitumen droplets that prevent them from joining each other. This makes bitumen dispersion in water more durable. The electronic charge of bitumen emulsion decides on what kind of surface it should be used. Some aggregates (such as marble aggregates) mix well with anionic bitumen emulsion and some others are a better solution to cationic bitumen emulsion (such as granite aggregates).
How is it produced?
Bitumen emulsion is usually made using a collide mill, which mixes bitumen with water and emulsifier. In this process, bitumen is milled into very small droplets that can easily suspend in the water. With the addition of emulsifiers, bitumen droplets become more water friendly. Water droplets as well move closer to the tiny droplets of bitumen, making sure that the final bituminous product is stable enough.
In the manufacturing process, many factors such as droplets’ size, chemical addition, and the temperature of various components are accurately controlled. The resulting bitumen has a consistent structure that makes it unique for various applications.
What are Different Types of Bitumen Emulsion?
Various emulsions are classified based on two main factors: particles’ electrostatic charge and breaking or setting time. In an emulsion, if the particles’ charge be negative, it is called Anionic and introduces itself wit letter “A”. Otherwise, the bitumen is known as cationic and has the “C” letter.
The second grading system of bitumen emulsion is closely related to the application. When applied to a surface, it must break and set. Technically, breaking means the evaporation of water, which makes bitumen strong enough for sticking to aggregates and setting on the place of application.
The time that is needed for it to lose water and behave like an ordinary bitumen, is called the reactivity rate. This parameter determines whether the bitumen is rapid setting emulsion, medium setting emulsion, and slow setting medium.
Another factor that can affect the reactivity of bitumen emulsion is the temperature of the surface onto which it is applied. In a hot weather, evaporation of water can accelerate. Both cationic and anionic bitumen emulsions are categorized according to the setting time.
What Factors are Important in Grading?
The first vital factor for grading is the viscosity value. The viscosity is determined by its bitumen content. An emulsion with small droplet size and a narrow distribution will give a higher viscosity.
To indicate the bitumen resistance to breaking, a ductility test is done. This testing system measures the extent to which a sample of bitumen can stretch before breaking. A bitumen emulsion that its ductility is more than 40 cm makes the surface of a road safe and strong to heavy traffic and do not break easily.
The softness level of bitumen is indicated by entering a standard needle into it. The harder the bitumen, the better it is for using in hot temperatures. The standard range of penetration can vary among different grades of bitumen emulsion.
This parameter evaluates the stability of bitumen emulsion during the storage. known also as sedimentation, storage stability shows if the bitumen emulsion droplets settle after manufacturing or not. For testing the sedimentation of bitumen emulsion, a sample of bitumen is stored in a cylinder in the room temperature. After 24 hours, two sample will be taken, one from the top of the cylinder and the other from the bottom. The weight of two samples will be compared at the next stage. The difference between two samples’ weight should not exceed 1 unit. Two main factors that affect the storage stability of bitumen emulsion are viscosity level and the droplet size. A bitumen with smaller droplets has less risk of settlement.
Various Standard Specifications Of Cationic Emulsion Bitumen Grade
Various Standard Specifications Of Anionic Emulsion Bitumen Grade