Modified Bitumen Membrane lv.2
“A viscous liquid, or a solid, consisting essentially of hydrocarbons and their derivatives, wich is soluble in trichloro – ethylene and is substantially nonvolatile and softens gradually when heated.” it is black or brown in colour & possesses waterproofing and adhesive properties.
Chemical Compostion of Bitumen
Bitumen is defined as a viscous liquid, or a solid consisting essentially of hydrocarbons and their derivatives, wich is soluble in carbon disulphate. Bitumen is a mxture of about 300 – 2000 chemical components, with an average of around 500 – 700. elementally, it is around 87 to 92% carbon and 6 to 8% hydrogen, and up to 5% sulphur, 1% nitrogen, 1% oxygen.
Production of Bitumen
- Bitumen is Manufactured from crude oil.
- Bitumen is obtained as the last residue in fractional distillation of crude
- The haviest material obtained from the fractional distillation process is further treated and blended to ake different grades of paving grae bitumen
Properties of Bitumen
- They contain predominantly hydrocarbons, with small quantities of sulphur, oxygen, nitrogen and metals.
- They are predominantly soluble in carbon disulphide (CS2) the portion insoluble in CS2 being generally less than 0.1%
- Most bitumens are colloidal in nature
- Bitumens are thermoplastic, i.e. they soften on heating and harden on cooling.
- They have no specific melting point, boiling point or freezing point, though a from of softeing point is used in their characterization.
- Bitumens are insolube in water
- They are highly impermeable to the passage of water.
- They are generally hydrophobic(water-repellent), but may be made hydrophilic(water liking) by the addition of small quantity of surface active agents.
- They are chemically inert.
- They oxidize slowly.
Advantage of Bitumen
- They are more tolerant.
- They can be used in relatively cold weather.
- They are ideal for patching and repair work.
- They are useful for sealing cracks.
Penetration test
- To determine the penetration grade of bitumen to be used for road construction.
- It gives the choice to select the grade of bitumen according to the climate condition of the area where the road is to be constructed.
- Consistency of a bituminous material expressed as the distance 1/10th of mm that a standard needle vertically penetrates a sample under standard conditions of load, time and temperature.
- Standard test condition:
temperature: 25°C
Load on needle: 100 grams
Time in which penetration are recorded: 05 seconds
Procedure:
- Temperature raised up to 100°C above its softening point.
- Sample is cooled to a temperature of 5°C.
- Place the sample in the penetrometer.
- Standard needle is approximately 50mm in length and 1.00 to 1.02mm in diameter.
- At least three penetration are carried out, then the nearest whole value unit the average of the three penetration, whose values do not differ maximum by 8, gives the penetration value of the bitumen.
