The original purpose of bitumen emulsion was to facilitate working with hot bitumen as well as to stabilize and blend it with moisturized material at room temperature.
Emulsion involves a combination of two liquids that do not blend into a single liquid. The small droplets of one liquid are evenly dispersed in the other.
Bitumen emulsion consists of bitumen droplets that are distributed in the water phase of production. It also includes active surface agents known as emulsifiers, necessary to prevent the merging of bitumen particles.
The most common bitumen emulsions are comprised of 60% bitumen and 40% water. Emulsion is blended with construction materials necessary for construction projects. After that, water vapors and bitumen particles are merged and spread evenly along the surface of rock material. This phenomenon is called “emulsion breaking.”
The following factors have a great impact on this process:
- the chemical composition of the emulsion;
- mechanical damages, caused by excess pump pressure, blending and compression;
- chemical coagulation, caused by the reaction between emulsion and rock material; and
- water loss during evaporation or absorption by miscible material.
Types of Emulsion
There are anionic and cationic bitumen emulsions. They are distinguished by the negative or positive charge of bitumen suspended particles in the suspension phase. Bitumen particles of anionic bitumen emulsions have a negative charge in an alkali phase, while bitumen particles of cationic emulsions have a positive charge in the acid phase.
Both anionic and cationic types of emulsion are blended with special emulsifier substances to increase the time for breaking.
Bitumen Emulsion Production
There are two types of equipment for bitumen production: continuous and batch. A colloid mill is considered to be the main part of this equipment. It provides for super fine grinding of bitumen particles and for even distribution in the water phase.
GlobeCore colloid mills have additional micropatterns on the surface of their rotors and a stator that together tear apart the particles of the product being processed.
This process favors the production of super stable bitumen emulsions that meet the international standards of the international road construction industry.
Application of bitumen Emulsions
To perform proper recycling with bitumen emulsion, it is necessary to provide and/or create the following conditions:
- Mixture Design: It is very important to determine the flow of bitumen emulsion and necessary to provide the desired strength characteristics. When working with different materials, the rate of flow of bitumen emulsion will be different;
- Treatment: Bitumen emulsion is a material that is sensitive to temperature and pressure. It is therefore, necessary to have information on the separation of bitumen from water in order to prevent such a phenomenon at the construction sites. To choose a proper emulsion, one should know everything about the working conditions on the construction site:
- Fluid quantities: During the recycling, it is very important to control the amount of water allocated as a result of emulsion breaking;
The humidity of the recycled material is of no less importance.
- Time for compaction: During the emulsion breaking, bitumen transits from a suspension state to a viscous state. Some particles of the recycled material are partially enveloped by a solid film of cold viscous bitumen that prevents compaction, so it should be completed before the emulsion breaking.
- Quality control: To monitor the quality, it is necessary to take samples just after the application of a recycler.
They are prepared before the emulsion breaking to fully model the compacted material of the road pavement.
- application of bitumen solidification;
When stabilizing the pavement with bitumen emulsion, some materials can acquire the necessary strength relatively fast (about a month).
Other materials acquire the necessary hardness value in a year.
The main factors that influence the time of acquiring the necessary strength, include:
- type and the quality of bitumen emulsion;
- moisture of material during compaction;
- achieved density;
- type of the material, its granulometric composition and absorption properties; and
- the amount of lime or cement added.
Through experimentation, it has been proved that cement has a great impact on the strength development of bitumen. At the same time, cement has an adverse effect on the fatigue characteristics of the stabilized layer. Consequently, the quantity of cement is limited to between 2