Bitumen modification is most used in a production of high quality materials for road construction and repair of highways, as well as roofing of buildings. It would therefore be useful to consider this product more carefully.
What is bitumen modification? Scope of use.
Bitumen modification is a water insoluble black substance that contains high molecular weight hydrocarbons and their derivatives. It generally is in a solid or resinous state.
Bitumen mixtures use natural and artificial ingredients. Natural bitumen is formed from natural oxidative polymerization of petroleum. Artificial bitumen is a result of modern upgrading processing of “black gold”.
Natural bitumen was used by Assyrians and Babylonians as far back as 3000 BC. Artificial bitumen was first obtained in 1898 from oil residues heated to a temperature of 300-320 ° C and oxidized by air.
Today, the main application of bitumen is in road construction and industrial construction (repair of roads and airfields, roofing, insulation of pipelines, obtaining paintwork materials).
Why do bitumen properties require improvement?
In the road industry, bitumen is needed to bind mineral materials that form road surfaces (sand, gravel, etc.), improve hydrophobic properties of concrete and fill gaps. Bitumen as a surface is affected by a number of negative factors: temperature changes, solar radiation, air oxygen, intensive loads from moving transport. As a result, the road surfaces prematurely lose integrity due to the destruction of bitumen.
Bitumen, as a building material:
- sensitive to changes in ambient temperature, becoming soft in the heat, and brittle in the cold;
- has low elasticity and insufficient mechanical characteristics;
- is prone to aging.
Methods for improving bitumen properties
The properties of any substance, including road bitumen, can be improved in two different ways: by changing the technology of production or an upgrading of the finished product. The first approach requires the restructuring of the production line, starting from the preparation of the raw material and finishing with the type of equipment used. To change every part of the production at one time and with minimal financial costs is impossible. Therefore, preference is given to the second approach by modifying bitumen.
Bitumen modification – origin and formation
First time bitumen modification was tried in the 30s of the last century in several countries of Western Europe. Small sections of highways were covered with modified bitumen. The first modifier was natural rubber.
Further research in this area was aimed at finding new modifiers. Twenty years later, Canada and the United States, began to use neoprene rubber as bitumen modifier, which was an emulsion based on synthetic rubber and water. Even then, there was a positive effect of modified bitumen on asphalt concrete fatigue endurance in heavy traffic conditions.
The new material attracted a great interest, which substantially expanded its area of application. Since the 1970s, modified bitumen has been used not only for the preparation of asphalt concrete, but also for surface treatments.
Benefits of bitumen modification
Bitumen modification obtains a building material that has the following performance properties:
- binds well with mineral materials;
- flexible and elastic at low-temperature, and resists deformation at high temperatures;
- quickly absorbs thermal and turbulent stresses in asphalt layers of pavement;
- resistant to fatigue loads during temperature changes;
- wide plasticity interval and wider service temperature interval;
- better mechanical properties and hardness.
Modifiers for bitumen
The most used substances in bitumen modification are thermoplastic polymers, rubbers and rubber resins, and thermoplastic elastomers.
Thermoplastic polymers have the ability to soften with increasing temperature and solidify when temperature drops. Such phenomena can be explained by their molecular structure, which has a linear character. Heating weakens the bond between the molecules, making thermoplastics into a soft viscous material. Among the thermoplastic polymers for bitumen modification are polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), viscoplastic and thermoplastics.
Crumb rubbers and rubber resins differ from other polymers in their ability to elongate up to 10 times with an applied load and to return to the initial state when the load is removed. This ability is explained by the structure of rubber macromolecules which are coils and extend like a simple elastic string. Also rubber molecules are so long, like ropes that they bend and coil randomly.
Rubber modifiers used improve the properties of bitumen are styrene butadiene rubber (SBR) and ethylene-propylene polymers, as well as butyl rubber.
Thermoplastic elastomers (TPE) have elastic properties for adhesive application. The production of TPE is established in many industrialized countries. Modifiers of this type are available in the form of granules and powders.
Styrene butadiene diblock copolymers (SB) styrene-butadiene-styrene polymers (SBS), styrene-isoprene-styrene polymers (SIS) and styrene-ethylene / butylene-styrene polymers (CE / BS). SBS polymers are used in the modification of road and roofing bitumen, SIS polymers are used as mastics for joints and cracks, and CE / BS polymers increase resistance of bitumen in unfavorable atmospheric conditions.
SBS polymer additives for bitumen modification provide:
- deformation resistance of asphalt concrete at various ambient temperatures;
- durability of road surfaces regardless of climate conditions and traffic loads.
There are three types of thermoplastic elastomers:
How to modify bitumen
The quality of road and roof surfaces depends not only on the components, but also on the technology of bitumen modification. The special equipment UVB-2 produced by GlobeCore have the capacity 6 – 22 m3 / h.
Bitumen modification happens in a colloid mill, which performs preliminary mixing of bitumen and polymer, and homogenization. One more function of the colloid mill as part of this equipment is grinding components. This optimizes the design of the unit by eliminating additional nodes.
The colloid mill is designed so that grinding and homogenization is realized in one passage of products through the mill, and the fineness of grinding is regulated by changing the gap between the rotor and stator.
UVB-2 is design specifically for bitumen modification and can implement any modification scheme, working with all known polymer additives and their forms.
In addition to bitumen modification units, GlobeCore also produces laboratory equipment that successfully operates in scientific research laboratories. Also, laboratory bitumen modification units are used by road construction organizations to obtain samples for future testing.