Test: Bituminous Material

The guidelines for the penetration test have been laid down in IS 1203. As per the same, the time allotted to the needle for penetration into the sample is 5 seconds. There are machines that automatically stop the penetration at the end of 5 seconds.

Revelling: It is characterized by progressive disintegration of the surface due to the failure of the binder to hold the material together.
The following are the causes of raveling:

• Insufficient binder in the mix.
• Inadequate compaction during construction.
• Construction during wet weather leads to the stripping of binder from aggregate.
• Construction during cold weather results in fracture, crushing, and opening of new faces.
• over-heating of mix or the binder.
• Improper coating of aggregates by binder

The indirect test consists of the determination of time taken by 50 mL of sample in the fluid state to flow through an orifice in a cup. This is carried out under standard test conditions and specified temperatures. Modified bitumen consists of additives and cannot be subjected to this test.

Bitumen

• Bituminous materials consist of bitumen which is a black or dark-colored solid or viscous cementitious substance consisting chiefly of high molecular weight hydrocarbons derived from the distillation of petroleum or natural asphalt. It has adhesive properties and is soluble in carbon disulfide.
• Tars are residues from the destructive distillation of organic substances such as coal, wood, or petroleum and are temperature sensitive than bitumen.
• Bitumen is soluble in petroleum oils where, unlike tar.

In IS 73:2013, the softening point of various grades of bitumen are noted down. There are four grades of bitumen and corresponding softening points are mentioned in the code. For VG 10, it is 40; for VG 20 – 45; for VG 30 – 47 and for VG 40 – 50.

Various tests conducted on bitumen for testing its various properties are as follows:

Marshal test is used for designing the bituminous concrete for pavement construction, Beckenham Beam Method is used to determine the deflection of the pavement slab.

Briquette mould is metallic and can be split into two halves. Bitumen is filled in the mould after it is fixed properly. Block mould is made of silicone and can be used for casting items. Urethane mould and latex mould can be used for casting concrete or plastic.

IS 1210-1978 is used to refer to procedure and specifications for conducting float test. IS 1209 is used for flash and fire point test, IS 1211 for determination of water content and IS 1212 for determination of loss on heating.

Ductility of bitumen is measured by the distance by which the bitumen gets elongated before breaking. It is expressed in cm. the sample in the mould is allowed to stretch gradually and the distance is read using the scale in the apparatus.

Tar can be of five types based on its viscosity. They are RT-1, RT-2, RT-3, RT-4 and RT-5. RT-1 has the least viscosity and is used for surface painting in extremely cold weather, RT-2 is used for standard surface painting in Indian climate, RT-3 is used for renewal coats, RT-4 is used for premixing tar macadam in the base course and RT-5 is used for grouting.