In the first place, we have to say that bitumen Emulsion has generally two types which are anionic and cationic.
To explain more, cationic emulsion bitumen types became popular from 1951 onwards and, due to their properties,
quickly replaced anionic bitumen types.
Generally speaking, water and bitumen do not mix, but emulsion bitumen technology
has made it possible for a significant percentage of bitumen to disperse in the continuous phase of water.
In other words, a compound which is an emulsifier keeps bitumen particles
charged (electrically charged) and suspended in a continuous phase of water.
The combination of bitumen emulsion grades
As a matter of fact, in the mixture, bitumen (which should only be 50-40, 70-60, or 100-85 industrial grade)
does not dissolve in water but floats in the water in the form of very small cells.
In some cases, we can use a stabilizer in conjunction with the emulsifier.
Largely, bitumen emulsion types are liquid-in-liquid emulsions in which the bitumen disperses in the water phase.
Important to know that in this type of bitumen , the amount of bitumen depends on its application,
which usually varies from a minimum of 52% to a maximum of 69%.
Important to realize that emulsion has three categories in terms of breaking rate, which are rapid breaking (RS), slow breaking (MS),
and slow breaking (SS). Moreover, it divides into three types in terms of bioelectricity of bitumen particles: cationic (C),
anionic (A) and amphoteric or neutral.
Since emulsifiers are active surface chemicals, they determine the electric charge of the emulsion.
Additionally, in the preparation of emulsion bitumen, we add a small amount of this chemical
to facilitate the formation of bitumen cells and permanent suspension.
Needless to mention that most binders in emulsion surface asphalts are cationic,
this means that bitumen particles in these emulsions have a positive charge.
Note that the positive ions that surround the bitumen particles in this emulsion adhere to them in contact
with rock materials and attach the bitumen particles to the materials by establishing an ionic bond.
Consequently, the beginning of bitumen adsorption is the beginning of emulsion failure and with the beginning of failure,
bitumen particles stick to the materials and each other and get bigger and bigger.
To clarify, this process fails faster with the compaction of materials or the use of accelerators.
Emulsion bitumen properties
- First thing to mention is the possibility of transportation to distant places in bulk (by bitumen tanker, truck, and trailer) or barrel (preferably oil barrel).
- Second, is the ability to use asphalt with low thickness.
- Third, high spreading speed of surface or thin asphalt as well as increasing asphalt operation due to drying in less than 2 hours.
- Finally, it is suitable for any type of asphalt, foundation, and coating (street-highway-airport runway).