Bitumen CSS1

Whatever the end use, application conditions usually require bitumen to behave as a mobile liquid. In principle, there are three ways to make highly-viscous bitumen into a low-viscosity liquid:

• Heat it
• Dissolve it in solvents
• Emulsify it

Bitumen emulsions are two-phased systems consisting of bitumen, water, and one or more additives to assist in formation and stabilization and to modify the properties of the emulsion. The bitumen is dispersed throughout the water phase in the form of discrete globules, typically 0.1 to 50 microns in diameter, which are held in suspension by electrostatic charges stabilized by an emulsifier. Bitumen emulsions can be divided into four classes. The first two are, by far, the most widely used:

• Cationic emulsions
• Anionic emulsions
• Non-ionic emulsions
• Clay-stabilized emulsions

The terms anionic and cationic stem from the electrical charges on the bitumen globules. This identification system originates from one of the fundamental laws of electricity – like charges repel, unlike charges attract. If an electrical potential is applied between two electrodes immersed in an emulsion containing negatively charged particles of bitumen, they will migrate to the anode. In that case, the emulsion is described as “anionic”. Conversely, in a system containing positively charged particles bitumen, they will move to the cathode and the emulsion is described as “cationic”. The bitumen particles in a non-ionic emulsion are neutral and, therefore, will not migrate to either pole. These types of emulsion are rarely Bitumen emulsions are divided into three categories in terms of setting:

• Rapid-setting (RS)
• Medium-setting (MS)
• Slow-setting (SS)

Cationic RS emulsion is currently the widely used category in Iran. Emulsion setting is irreversible phenomenon which may occur due to the evaporation of the water phase or the attraction of water by stone materials. Throughout this phenomenon, the water phase disappears and bitumen particles will have less space. Then, the bitumen gradually moves towards the surface or coats the aggregate. Cationic Emulsions These emulsions are known as cationic because their bitumen aggregates carry positive charges by using Ammonium salts or Amines compounds. They are divided into the following categories:

Cutback Bitumen is by Adding Controlled Amounts of Petroleum Distillates Such as Kerosene. This is Done to Reduce the Viscosity of the Bitumen Temporarily so it Can Penetrate Pavements More Effectively or to Allow Spraying at Temperatures that are too Cold for Successful Sprayed Sealing with Neat Bitumen. The Materials Used to Cutback Bitumen Will Evaporate After Application to Leave the Remaining Material Similar in Hardness to the Original Bitumen Cutback Bitumen Applications is Asphalt Pavement Construction, Maintenancem, Prime and Tack Coating and ...

Bitumen emulsions are basically an O/W – Oil on Water solution – A dispersion of bitumen particles on water phase, stabilized with the addition of surfactants – Surface active agents – or most commonly known as emulsifiers. They are 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, other cold mixed asphalt and maintenance binder . Bitumen emulsions are divided into three categories: * Anionic with negatively charged globules * Cationic with positively charged globules * Non-ionic with neutral globules. Base on the time of setting after spraying, Bitumen emulsions classification as Quick Set (QS), Rapild set (RS), Medium set (MS) and Slow set(SS)