Bitumen itself comes from the fractional distillation of crude oil, but that is not the only way of acquiring it, it also exists as deposits naturally. It’s a unique combination of excellent water-proofing, and adhesive properties make it stand out. Therefore, bitumen is being used for various purposes. There are so many benefits to this low-cost thermoplastic material, as its usage in roofing, road and pavement applications. However, in cold environments, it is brittle and in warm climates softens readily.
Modifying bitumen with polymers is one of the many ways of toughening it.
The polymer used in the process of modification can be, either virgin or scrap, to produce polymer modified bitumen (PMB).
Polymer Modified Bitumen (PMB) Additive
Polymer Modified Bitumen (PMB) Additive, it is a functional polyolefin that is used to modify asphalt.there are different uses to The Polymer Modified Bitumen (PMB) Additive, a. making hot bitumen mixtures (BSK) b. Binder coating. C. Corrosion coatings.
The Polymer Modified Bitumen (PMB) Additives are also helpful for preventing permanent wheel tracks as well as cracks on roads.
Advantages
· You can get the best results according to the AASTHO M320 / EN 14023, standards regarding its softening point and to settle performance of wheel track when being used as a “hybrid” with the SBS polymer.
· The melting point on it is low. The Polymer Modified Bitumen (PMB) Additive tends to melt quickly within bitumen under 130-140 °C. With applying only a basic mixture, it can melt within bitumen quickly and distribute homogeneously.
· With the Polymer Modified Bitumen (PMB) Additive, the machinability of modified asphalt will not get difficult as in asphalt modified with SBS, and its machinability is much more comfortable in comparison with SBS modification.
· the elastic module of the asphalt increases, which is a great value, material fatigue, Marshall stability, and indirect tensile strength.
· It raises the peeling strength and cohesiveness of asphalt.
· It is compatible with any types of bitumen having different characteristics.
· The price of it is more economic and has more stability in price when compared to SBS.
· It is the most efficient solution in the prevention of wheel tracks, and it does not change even in the worst environmental temperature.
· Having perfect storage stability.
· The polymers are immune to decomposition during storage.
· With polymer, the resistance of asphalt will increase against fuels and solvents.
Application
· It is capable of being added to both bitumens in prior or directly adding to the plant mixer.
· Dosage varies between 3% - 5% of the bitumen weight by asphalt design calculation.
· The typical temperature for mixing it with bitumen is It is under 150 °C. then it becomes easy for it to melt and then distribute within the asphalt.
· It is recommended, especially for use in crossways, bus lines and bus stops, runways, airport taxiways, industrial facilities, and container storage.
The benefits of modified asphalts
Highway agencies know modified asphalt for a more economically efficient material; they also recognize it as a more secure pavement.
Enhancing rutting resistance and is the primary benefit of this type of asphalt in addition to less thermal (cold-temperature) cracking and improved mixture durability.
Some particular modified types can enhance the bitumen resistance towards moister damage (stripping).
Many agencies have estimated that modified bitumen binder can help increase the life of bitumen by four to six years.
Changing times
Agencies are continually trying to prolong the service life of pavements. These days the traffic demands regarding our roadways are considerably more severe than they were in the past.
The AASHO Road Test (1958-1962) is still very popular with pavement design. That study was based on a legal load limit of 73,280 pounds. In 1982, they raised the load limit to 80,000 pounds – which apparently is not a huge increase. However, technically that 10 percent load-level increase is equal to 40 to 50 percent more stress to the pavement.
There is also one more change that has brought higher demands to the pavement, the introduction of radial truck tires. The pavement contact pressure of the Bias-ply tires is about 75 pounds per square inch (psi). 125 psi of pressure is how much Radial truck tires applies to today’s pavements.
Due to the increase of truck traffic volume modified binders are a better solution to meet this challenge
What is Useful Temperature Interval (UTI)?
This concept means the spread between the PG high and low-temperature classifications.
The UTI “Rule of 92” indicates the modification of a binder. Also, in the case that the UTI is less than 92 degrees Celsius, then the asphalt binder is not modified probably. Most adhesives with a UTI value of 92 are modified, but there are a few crude sources that might meet this value without modification.
If the UTI is greater than 92, the binder is probably modified. For instance, the commonly used PG 76-22 grade has a UTI value of 98 degrees Celsius (76°-(-22°)) so is considered as a modified binder.