An emulsion is a two-phase system consisting of two immiscible liquids (unmixable or unblend able). The dispersed or internal phase is the liquid that is broken up into globules and the surrounding liquid is known as the continuous or external phase. Oil-in-water emulsions have the oil as the dispersed phase and water as the continuous phase. The reverse occurs when the emulsion is of water-in-oil type. Oil phase consisting of bitumen or tar.
In the preparation of emulsion of asphaltic bitumen or tar, emulsifiers have to be added in small proportions both to facilitate the formation of dispersion and to keep the globules of dispersed binder in permanent suspension. If no emulsifier is present, a dispersion of oil droplets in water brought about by stirring will rapidly separate into 2 layers. With emulsifier present, an adsorbed film of the emulsifier is formed round each globule in the emulsion. Emulsion are classified in to 3 types based on setting time:
1. Rapid setting: If the bitumen emulsion is intended to break rapidly, the emulsion is said to possess rapid-set quality and this type is used in surface dressing & penetration macadam.
2. Medium setting: Emulsion which does not break spontaneously on contact with stone but break during mixing or by fine mineral dust are MC. Used in premixing with coarse aggregate.
3. Slow setting: When specified type of emulsifying agent is used to make the emulsion relatively stable, they are called slow setting grade. Used in surface course along with the coarse aggregate.
Bitumen emulsions are divided into three categories:
- Cationic bitumen emulsion
cationic emulsion are positively charged, so this bitumen emulsion adheres better to rocky materials including silica and quartz compounds having negative electric charge. In cationic emulsion bitumen, breaking is performed chemically. In order to the lowest time breakings, the average and commonly used of emulsions is cationic types.
- Anionic emulsion
If the bitumen particles have a negative charge, this type of emulsion will stick to the calcareous rock material having a positive charge. Unlike cationic emulsion bitumen, anionic emulsion bitumen do not undergo chemical breakdown and may have to evaporate water due to emulsion breakdown which is less commonly used today due to their poor performance.
- Non-ionic emulsion
Non-ionic emulsion bitumen are mainly used in industrial applications and are not used in construction.
In the preparation of emulsion of asphaltic bitumen or tar, emulsifiers have to be added in small proportions both to facilitate the formation of dispersion and to keep the globules of dispersed binder in permanent suspension. If no emulsifier is present, a dispersion of oil droplets in water brought about by stirring will rapidly separate into 2 layers. With emulsifier present, an adsorbed film of the emulsifier is formed round each globule in the emulsion. Emulsion are classified in to 3 types based on setting time:
| BITUMEN CSS-1h | |||
| Property | Min | Max | Test Method |
|---|---|---|---|
| Viscosity, Say bolt Furol at 25°C,SFS | 20 | 100 | ASTM D244 |
| Storage stability Test, 24-h, % | – | 1 | ASTM D6930 |
| Particle Charge Test | Positive | ASTM D244 | |
| Sieve Test, % | – | 0.1 | ASTM D6933 |
| Cement Mixing Test,% | – | 2.0 | ASTM 6935 |
| Distillation | |||
| Residue % | 59 | – | ASTM D244 |
| Test On Residue From Distillation | |||
| Penetration, 25°C(77°F), 100g, 5s | 40 | 90 | ASTM D5 |
| Ductility, 25°C(77°F), 5 cm/min, cm | 40 | – | ASTM D113 |
| Solubility in trichloroethylene, % | 97.5 | – | ASTM D2042 |
| BITUMEN K160 | |||
| Property | Min | Max | Test Method |
|---|---|---|---|
| Viscosity, Say bolt Furol at 50°C,SFS | 20 | 100 | ASTM D244 |
| Storage stability test, 24-h, % | – | 1 | ASTM D6930 |
| Demulsibility, 35 ml, 8% Dioctyl sodium sulfosuccinate, % | 40 | – | ASTM D6936 |
| Particle Charge Test | Positive | ASTM D244 | |
| Sieve Test, % | – | 0.1 | ASTM D6933 |
| Distillation | |||
| Solvents, By Volume Of Emulsion % | – | 3 | ASTM D6997 |
| Residue % | 60 | – | ASTM D244 |
| Test On Residue From Distillation | |||
| Penetration, 25°C(77°F), 100g, 5s | 100 | 250 | ASTM D5 |
| Ductility, 25°C(77°F), 5 cm/min, cm | 40 | – | ASTM D113 |
| Solubility in trichloroethylene, % | 97.5 | – | ASTM D2042 |
| BITUMEN K170 | |||
| Property | Min | Max | Test Method |
|---|---|---|---|
| Viscosity, Say bolt Furol at 50°C,SFS | 20 | – | ASTM D7496 |
| Storage stability test, 24-h, % | – | 1 | ASTM D6930 |
| Particle charge test | positive | ASTM D244 | |
| Sieve test, % | – | 0.1 | ASTM D6933 |
| Distillation: | |||
| Oil distillate, by volume of emulsion, % | – | 4 | ASTM D6997 |
| Residue, % | 67 | – | ASTM D6997 |
| Test on residue from distillation: | |||
| Penetration, 25°C (77°F), 100 g, 5 s | 60 | 250 | ASTM D5 |
| Ductility, 25°C (77°F), 5 cm/min, cm | 20 | – | ASTM D113 |
| Solubility in trichloroethylene, % | 97.5 | – | ASTMD2042 |
Packing
- Drum 208 litr (0.8 mm Thickness )
Application of Emulsion Bitumen
Each application places particular demands on the emulsion bitumen. 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.
Emulsion bitumen can be used under a wide range of conditions, namely:
- With dusty or damp aggregates for chip sealing;
- A rapid setting type emulsion is suitable for surface dressing and penetration macadam type of construction.
- With uncoated aggregates for chip seals, as the adhesion of the cationic emulsion type to a range of aggregates is normally sufficient;
- Application at lower temperatures in the interests of Medium setting type is used for premixing with coarse aggregates.
- In case of fine aggregates, the surface area of aggregate is more and as a result long duration of time is required to mix the emulsion.
- slow setting emulsion is preferred which gives sufficient time for uniform blending of the mix.
- Where lower application rates are required through the dilution with water.
ADVANTAGES & LIMITATIONS OF BITUMEN EMULSION
ADVANTAGES
- The main properties of bitumen are preserved in emulsion mixes since emulsions do not need hot mixing. Generally cold mixing or just slightly warming the ingredients of the emulsion mix are done for construction of pavements.
- Emulsion can be used in humid weather even when it is raining.
- Emulsions possess anti-stripping properties.
- Emulsions with lower viscosity or thinner consistency improve spreadability and allows better coating of the bitumen on the surface of aggregate.
- There is no depletion during laying and storage.
- Since emulsions are water based, there is less effect on the environment.
- It is the least energy intensive of all construction material: there is no need to heat.
LIMITATIONS
- Not a single type of emulsion is suitable for every work. It depends upon whether the aggregate is acidic or basic in nature.
- The setting time may vary depending on the air temperature, wind velocity and type of emulsion.
- There is a wide range of curing time; a suitable emulsion mix needs to be designed for a particular need, i.e. we need to determine for each case, the optimum quantity of emulsion based on zone, type of emulsion, mix grade and desired mechanical properties
- It has limited storage time (ranging from few days to six months)
Standards of Emulsion Bitumen
Standards all have the same basic purpose of setting out agreed principles or criteria, so in different regions and countries, different Standards and Grading systems are used for determining the qualities. Most commonly used standard specifications for bitumen emulsions (ANIONIC; CATIONIC; UNMODIFIED; POLYMER MODIFIED) are as below:
1 .American Society for Testing and Materials (ASTM) & American Association of State Highway and Transportation Officials (AASHTO)
- for Anionic Emulsions: ASTM D 977 and AASHTO M 140
- for Cationic Emulsions: ASTM D 2397 and AASHTO M 208;
- Polymer Modified Cationic Emulsion: AASHTO M 316
2 .European Committee for Standardization (CEN):
- Harmonized Framework Standard EN 13808 for Cationic Unmodified and Polymer Modified Emulsions; many different national.
3 .Australian Standard AS1160
4.Kenya Standard specification for bitumen read emulsions :(Anionic and Cationic) KS 02-769: 1990 standard
5. British Standards
- Specification for anionic bitumen road emulsions BS 434-1:2011+A1:2016
- Code of practice for the use of cationic bitumen emulsions on roads and other paved areas BS 434-2:2006
- (anionic and cationic). Specification for bitumen road emulsions BS 434-1:1984
