Introduction
Definition of Bitumen Emulsion
Bitumen emulsions are colloidal mixtures of bitumen and water. Due to the different surface tensions of the two liquids, stable emulsions cannot be created simply by mixing. Therefore, various emulsifiers and stabilizers are added. Emulsifiers are amphiphilic molecules that differ in the charge of their polar head group. They reduce the surface tension of the emulsion and thus prevent bitumen particles from fusing.[1]
Composition of Bitumen
An emulsifying agent is used to aid in dispersing the bitumen in water to form a bitumen emulsion. A typical bitumen emulsion is composed of several essential ingredients, each of which affects the performance and characteristics of the emulsion. Based on the table given, the following is a detailed description:
Bitumen
Role: Primary component providing the binding properties.
Details: Viscous road bitumens with penetration are commonly used (25 °C, 0.1 mm) 60–200; it is possible to use bitumen modified by polymers.[2]
Water
Role: Acts as the medium for dispersing bitumen.
Details: The use of hard water and the absence of mechanical impurities are not allowed. A large number of electrolytes can result in decay. Also, decay may occur on the surface of solids. The hardness of used water should not exceed 6 mEq/l.[2]
Emulsifier
Role: Facilitates the dispersion of bitumen in water.
Details: Anionic and cationic emulsifiers. The obtaining of three classes of emulsions - EBC-1,2,3.[2]
Acid
Role: Adjusts the pH and helps in forming the emulsion.
Details: Hydrochloric acid of 25–37%, the pH of the aqueous phase makes 1.5–3.5. It transfers the emulsifier into ionic form, allowing for adjustment of the pH of an aqueous phase and an emulsion.[2]
Solvent
Role: Increases stickiness and aids in film formation and dispersion.
Details: The introduction of a variety of solvents to increase the stickiness emitted during the decay of the bitumen emulsion (as the film-forming agent) and to facilitate its dispersion in water is possible.[2]
Modifier of a Disperse Phase
Role: Enhances the performance of the bitumen.
Details: Polymers may act as a modifier of a dispersed phase. They serve as the polymers that are used for an extended temperature range performance of viscous bitumen with the simultaneous increase of their heat and crack resistance and flexibility.[2]
Stabilizer
Role: Stabilizes the emulsion.
Details: Calcium chloride as 30–35% aqueous solution is often introduced as a stabilizer.[2]
Thinner
Role: Adjust the penetration of the bitumen.
Details: It is used to increase the penetration of bitumen up to the desired value. Vacuum gas oils, oil fractions are used, etc.[2]
Classification of Bitumen Emulsion
Emulsions can also be categorized by the rate at which bitumen droplets coalesce and return to bitumen. This is related to the rate at which the emulsion becomes unstable and breaks after mixing with aggregate and filler. Bitumen emulsions are divided into Rapid-Setting (RS), M-Setting (MS), and Slow-Setting (SS). In addition, bitumen emulsions are classified based on EN 13808, with various letters and numbers indicating viscosity and basic bitumen type. The table shows the abbreviations for cationic emulsions. For example, C69BF3 70/100 is a cationic bitumen emulsion made from 70/100 pen-grade bitumen with a 69% bitumen fraction containing more than 3% (m/m) flux and a breaking class 3.[3]
Cationic emulsion abbreviated description adapted from [3]
Rapid-Setting (RS)
A quick setting emulsified bitumen is used for penetration, surface treatment, tack coating, and mulch treatment.[4] Rapid setting (RS) grade emulsion has been divided into two different grades of emulsions. The nomenclature for the proposed emulsions has been indicated as RS-1 emulsion and RS-2 emulsion.[5]
M-Setting (MS)
A medium setting emulsified bitumen used for plant mixes with coarse aggregate, all of which is retained on a 2.80 mm IS Sieve with practically no material passing 75 microns IS Sieve.[4] M-Setting (MS) grade emulsion has been divided into two different grades of emulsions. The nomenclature for the proposed emulsions has been indicated as MS-1 emulsion and MS-2 emulsion.
Slow-Setting (SS)
A slow-setting emulsified bitumen used for fine aggregate mixes in which a
substantial quantity of aggregate passes a 2.80-mm IS Sieve, and a portion may also pass a 75-micron IS Sieve.[4] Slow setting (SS) emulsion has also been divided into SS-1 and SS-2 emulsion.[5]
