Cationic Bitumen Emulsion Description
Cationic Bitumen Emulsion is a stable dispersion of bitumen in water in the continuous phase. The bitumen globules are positively charged due to the NH3 + group cover which is formed around bitumen droplets and provides stability for emulsion by electrostatic repulsion. These bitumen droplets have an affinity with the negatively charged aggregate, which is usually available in India. Dispersion is obtained by processing bitumen & water-based solution under controlled conditions through a colloidal mill having a high-speed rotor in the presence of scientifically selected surfactants/emulsifiers. The selection of emulsifier & its quality is significant for emulsion stability, it’s breaking & curing when applied over aggregates. The Cationic Bitumen Emulsion is chocolate brown and free-flowing at normal temperature. Once it breaks the bitumen breaks out and color changes to black. An Emulsion is said to break when the organic and the aqueous phase separate into two distinct layers i.e. the dispersion ceases to exist. Emulsions are classified as Rapid Setting-1(RS-1), Rapid Setting-2(RS-2), Medium Setting (MS), Slow Setting-1 (SS-1), and Slow Setting-1 h (SS-1h). The breaking time varies according to the designation of Emulsion although being largely dependent upon the climatic condition i.e. temperature, humidity, wind velocity, etc.
The term cationic is derived from the migration of particles of bitumen under an electric field also. The droplets migrate toward the cathode (negative electrode), and hence the emulsion is called cationic. The cationic emulsifying agent functions similarly to the anionic; the negative portion of the head floats around in the water leaving a positively charged head. This imparts a positive charge to all the droplets. Since positives repel each other, all the droplets repel each other and remain as distinct bitumen drops in suspension. A typical cationic emulsifying agent is shown below showing the orientation of the agent at the bitumen-water interface and the positive charge imparted to each drop.
Cationic Emulsion Bitumen
Cationic type: In which the bitumen particles are positively charged and the emulsifier used is a long chain amine. These are suitable for use with siliceous aggregates like quartzite, sandstone, granite, etc.
When the emulsion is being produced the cations are adsorbed by bitumen droplets, negative ions remain in the water. The undeniably most complete field of use is represented by the rapid setting emulsions.
The choice of bitumen emulsion (i.e. whether anionic or cationic) to be used depends upon the mineral composition of aggregate used for construction. In the case of silica-rich aggregates, the surface of the aggregates is electronegatively charged. Therefore a cationic bitumen emulsion should be used. This will help better the spreading and binding of bitumen with aggregates.
Anionic Bitumen Emulsion Description
HJ Oil Group is a supplier of high-quality Anionic Bitumen Emulsion.
The preparation of bitumen emulsion is essentially the grinding of bitumen in water with a surfactant. Therefore, the emulsifier is one of the most important components of bitumen emulsions, which directly influences the quality and characteristics of the product. The emulsifier is a surfactant. By chemical nature, surfactants are divided into several types, depending on the charge of its particles. Since water bitumen emulsions are used intensively as binding and film-forming material in construction, two types of emulsifiers are used: anionic and cationic.
Chemical surface-active agents, which serve as emulsifiers, are classified by the electrochemical charge that is attained when they dissociate in a water solution. In the case of anionic emulsions, the chemical charge is negative. The chemical type and quantity of surface-active agent used in the manufacturing process govern the process in which the resulting asphalt emulsion can be used.
The term Anionic Bitumen Emulsion is derived from the migration of particles of bitumen under an electric field. The droplets migrate toward the anode (positive electrode), and hence the emulsion is called anionic. In an anionic emulsion, there are “billions and billions” of bitumen droplets with the emulsifying agent at the water bitumen interface. The tail portion of the emulsifying agent aligns itself in the bitumen while the positive portion of the head floats around in the water leaving the rest of the head negatively charged and at the surface of the droplet. This imparts a negative charge to all the droplets. Since negatives repel each other, all the droplets repel each other and remain as distinct bitumen drops in suspension. A typical anionic emulsifying agent is shown below along with a diagram showing the orientation of the agent at the bitumen-water interface and the negative charge imparted to each drop.
The difference is that the anionic bitumen emulsion is negatively charged, while the cationic emulsions are positively charged. The choice of emulsifier used in the preparation of the emulsions determines the efficiency and reliability of the product.
For certain reasons, cationic systems have a significant advantage over anionic emulsions. Most of the fillers used in road construction have a limited amount of positively charged particles, which can attract the negatively charged particles of the anionic emulsion. Therefore, it is more difficult to create a uniform structure and ensure a high degree of adhesion with an anionic surfactant. When using anionic emulsion, bitumen should be modified by additives, while in the cationic emulsion, the emulsifier itself serves as an adhesion additive.
Unlike cationic emulsions, which readily interact with alkaline and acidic minerals, anionic emulsions are less versatile and work well only with alkaline minerals.
The amount of emulsifier applied influences emulsion breakdown rate, i.e. the time until the bitumen precipitating from the emulsion, returns to its original state.
Bitumen Emulsion Description
Bitumen emulsion is a mixture of water & asphaltum. Hey wait, we know that bitumen is a oil product and it cannot be mixed with water. That is why we add an emulsifier (a surface active agent) with water before adding bitumen. Addition of emulsifier with water facilitates breaking of asphaltum into minute particles and keeps it dispersed in suspension.Therefore we can say that bitumen emulsions are a liquid product consisting of three things, (i.e. water + Emulsion + Asphaltum) where droplets of Asphaltum are suspended in water.
Bitumen emulsions are usually dispersions of minute droplets of bitumen in water and are examples of oil-in-water emulsions.
The bitumen content can be varied to suit different requirements and is typically between 30% and 70%. The primary objective of emulsifying bitumen is to obtain a product that can be used without the heating normally required when using cutbacks and paving grade bitumen. In the manufacture of bitumen emulsions, hot bitumen is sheared rapidly in water containing an emulsifying chemical (emulsifier). This produces very small particles of bitumen (the dispersed phase) dispersed in water (the continuous phase). The bitumen particles are stabilised in suspension and do not readily coalesce due to the presence of the emulsifier, which is concentrated on the surface of the bitumen particles. During application, the water in a bitumen emulsion is either lost by evaporation, or it may separate from the asphalt because of the chemical nature of the surface to which the emulsion is applied. This process is referred to as breaking. Because Asphaltum has a density only slightly higher than water, sedimentation of the Asphaltum droplets in an emulsion during storage is very slow. Emulsions can usually be regenerated after long storage times by gentle stirring to redisperse the bitumen droplets.
Composition and Different Types of Bitumen Emulsion
The bitumen emulsion is classified into two types:
1- Based on Setting Time
When the bitumen emulsion is applied on the aggregate for the road works the water evaporates leaving behind the asphalt droplets. These droplets spread on the aggregate and bind with each other and gains strength eventually.
Based upon the time taken by the vitamin emulsion to evaporate the water and between particles to separate from water, bitumen emulsion is further classified into 3 types based on setting time:
a) Slow setting emulsion
In this type of emulsion, a special type of emulsifier is used to slow the process of water evaporation. This type of emulsifier are relatively stable.
b) Medium setting emulsion
This type of bitumen emulsion doesn’t break as when applied on aggregate. The process of evaporation starts when the fine dust of mineral are mixed with the aggregate emulsion mix.
c) Rapid setting emulsion
This type of bitumen emulsion breaks down rapidly as it comes with contact with aggregate helping in fast setting and rapid curing.
2- Based on Surface Charge
Bitumen emulsion is a combination of water and asphalt. 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 an 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 affects the molecules of emulsion and lead to the categorization of it into Cationic and Anionic.
– Anionic Bitumen Emulsion
– Cationic Bitumen Emulsion
In anionic bitumen emulsion, the tiny droplets of bitumen are electronegatively recharged. In Cationic bitumen emulsion, the tiny droplets of bitumen are electro positively charged.
The average and commonly used emulsions is cationic between emulsions. Selection of positive or negative recharge between emulsions depends upon the mineral composition of aggregate on which it is used
Ex: In the case of silica-rich aggregates the surface of silica is aggregate is positively charged therefore cationic bitumen emulsion is used which helps in better spreading and binding of bitumen with aggregates.
The electronic charge of BE decides on what kind of surface it should be used. Some aggregates (such as marble aggregates) mix better with anionic bitumen emulsion and some others are a better solution to cationic bitumen emulsion (such as granite aggregates).
Both cationic and anionic bitumen emulsions are categorized according to the setting time. Look at the table below to find the various categories of bitumen emulsion and their globally standard names.
Bitumen Emulsion Applications
Emulsion Bitumens primarily used for tack coats for use in between hot mix asphalt layers and prime coats for thin hot mix surfacing layers or a chip seal pavements. Each application places particular demands on the emulsion. There is a considerable amount of variation between countries on the choice of emulsion for each application, but the table summarizes the most common practice. Anionic emulsions are hardly used outside North America for road construction but may be used for some industrial coatings.
– It can be used in damp environment on wet aggregates
– Road repair work can be carried out in minimum time
– Provides better tack coat with better workable conditions
– It can be used in any season
– Since heating is not required it can’t pollute air
– Long storage stability in clean containers/Tanks
Advantages and Uses of Bitumen Emulsions are:
- used extensively in bituminous road construction. Other than this they are used for maintenance and repair work.
- Emulsions can be used in wet weather even if it is raining.
- it Is ecofriendly as it is water based.
- used in soil stabilization in desert areas.
- It doesn’t need extra heat while placing.
- There is no wastage in placing and laying of bitumen.
- They possess anti-stripping properties.
- Rapid setting type of emulsion are used in surface of roads.
- Medium setting type of emulsion are used in premixing of bitumen and coarse aggregate.
- Slow setting type of emulsion are used with fine aggregates as the surface area is large and requires time for uniform mixing.