KNOWLEDGE BASE

Bitumen, being the cheapest binder available, finds extensive use in road construction. However, the physical and chemical properties of bitumen vary from refinery to refinery. Similarly, there is a vast variety of aggregate available in India. For eg. Marble, limestone, basalt, sandstone, granite, quartzite etc. These are classified as acidic or alkaline. They may also be classified as hydrophilic (water loving) or hydrophobic (water hating). These aggregate have different characteristics, properties, stripping values etc. Furthermore, due to the vast number of roads and highway projects, good quality aggregate is not always easily available. In India the Ministry of Road Transport and Highways has specified permissible stripping value of aggregate as 5% only, when tested as per IS 6241:1971. Any aggregate which has stripping value of more than 5% should either not be used in road construction or suitable remedial measure(such as addition of anti- stripping agent in bitumen) should be taken to bring the stripping value within permissible limit. Surface texture, porosity and absorption properties of aggregate also effect the adhesion to bitumen . In majority of the cases, the bitumen-aggregate bond is not sufficiently strong and complete by itself.

Antistripping agent, Super Bond XS , is the most effective and economical solution for providing a strong, durable and lasting binder-aggregate bond Anti Stripping Agent Supplier Thermoplastic Road Marking Paints in India.

Water - It's Damaging Effect :
Water is on of the most damaging factors responsible for premature failure of bituminous pavements. The various mechanisms by which water affects the pavements are:-

• Water form a thin, invisible film around the aggregate in the form of moisture during road construction. This obstructs the complete, strong coating of aggregate by bitumen. Therefore, when the initial bond itself is weak, the pavement is unable to take normal stress and disintegrates
• In post construction period, when water intrudes the surface of the pavement and penetrates between aggregate and bitumen film, it starts the process of stripping the binder from the aggregate.
• Pore pressure, which is the increased pressure caused by the circulation of trapped water through the void structure of aggregate also initiates stripping. The water may be present due to ground water ingress or surface intrusion.
• Hydraulic scouring which occurs on surface courses because of a compression tension cycle caused by the interaction of tire pressure with surface water

SUPER-BOND XS is extremely effective in considerably enhancing both Active Adhesion and Passive Adhesion Active Adhesion

ACTIVE ADHESION :
When the bitumen has the property to coat even wet aggregate, it is called active adhesion. This is essential at the time of construction, as this would result in a complete bond between bitumen and aggregate. Even thin film of moisture would cause improper weak bonding. It has been observed that active adhesion is possible only with the addition of a good quality anti stripping agent. The test for Measuring this adhesion is the under water coating test.

PASSIVE ADHESION :
In this case dry aggregate are first coated with bitumen and then immersed in water for 24 hours. Thereafter, if the bond/ coating of bitumen and binder stays intact, and there is minimum damaging effect of water, it is called passive adhesion. The test for measuring passive adhesion is as per IS 6241-1971. In practice this bond starts weakening after some time but by incorporating Super Bond XS in the binder the bond remains intact and there is no stripping of bitumen from aggregate surface.