To determine specific gravity, flash & fire point and ductility of bitumen.

OBJECT:

1. To determine the specific gravity of the given bitumen sample by the Balance method.
   
2. To determine the flash and fire point of the given bitumen sample.
   
3. To determine the ductility value of the given bitumen sample
   
   
   

1.SPECIFIC GRAVITY TEST OF BITUMEN (AASHTO T-228, ASTM D-70)

EQUIPMENT:

Specific gravity bucket, balance machine, and water tub.

THEORY:

The density of the bitumen binder is a fundamental property frequently used as an aid in identifying the binder for use in paving jobs. In most applications, the bitumen is weighed, but finally, in use with an aggregate system, the bitumen content is converted on a volume basis. Thus an accurate density value is required for the conversion of weight to volume.

The specific gravity is greatly influenced by the chemical composition of the binder increased amount of aromatic-type compounds causes an increase in the specific gravity. The specific gravity of all types of bituminous materials could be determined by the pycnometer method. However, the bitumen which is semi-solid state at 27^oC can be tested by the balance method. If the bituminous material is in liquid form at 27⁰C, the specific gravity may be found by the pycnometer method by completely filling the specific gravity bottle with the liquid material.

Specific Gravity:

“It is the ratio of the mass of a given volume of the bituminous material to the mass of an equal volume of water, the temperature of both being specified as 27⁰C.”

PROCEDURE:

1. Make a cube-shaped bitumen specimen of about 12 mm on each edge
   
2. Prepare it by pouring the liquefied bitumen sample into the brass mould to provide the sample of the required dimensions and then it is cooled. Keep it in a water container for at least half an hour at a temperature 27⁰C.
   
3. Weight the sample in air and weigh it again in the distilled water maintained at 27oC to the nearest 0.1 mg.
   

CALCULATIONS:

Balance Method:

Specific Gravity =

Where,

e = weight of the dry specimen.

f = weight of the specimen when immersed in distilled water.

RECOMMENDED VALUES:

The specific gravity of pure bitumen ranges from 0.97 to 1.02. According to International Standard (I.S) minimum specific gravity of paving bitumen at 27°C.

RESULT:

2.FLASH AND FIRE POINT TEST (AASHTO T-48, ASTM D-92)

EQUIPMENT:

Cleve land Flash and Fire point apparatus (It consists of a cup, heating plate, thermometer clip and test flame).

THEORY:

The Flash and Fire point test is a safety test conducted on a bituminous material so that it indicates the critical temperature at and above where precautions should be taken to eliminate fire hazards during its applications. Bituminous materials leave out volatiles at high temperatures depending upon their grade. These volatile vapors catch fire causing a flash. This condition is very hazardous and it is, therefore, essential to qualify this temperature for each bitumen grade, so that the paving engineers may restrict the mixing or application temperature well within the limits.

Flash Point:

The flash point of a material is the lowest temperature at which the vapour of a substance momentarily takes fire in the form of a flash under specified conditions of test.

Fire Point:

The fire point is the lowest temperature at which the material gets ignited and burns under the specified conditions of the test.

PROCEDURE:

1. All parts of the cup are cleaned and dried thoroughly before the test is started.
   
2. The material is filled in the cup up to a mark. The lid is placed to close the cup in a closed system. All accessories including thermometers of the specified range are suitably fixed.
   
3. The bitumen sample is then heated. The test flame is lit and adjusted in such a way that the size of a bed is 4mm in diameter. The heating of the sample is done at a rate of 5° to 6°C per minute. During heating the sample the stirring is done at a rate of approximately 60 revolutions per minute.
   
4. The test flame is applied at intervals depending upon the expected flash and fire points and corresponding temperatures at which the material shows the sign of flash and fire are noted.
   

Figure: Cleveland Flash and Fire Point Tester.

RESULT:

3. DUCTILITY TEST OF BITUMEN (AASHTO T-51, ASTM D-113)

EQUIPMENT:

Briquette Mould, Water bath, Ductility Machine, and Thermometer

THEORY:

The ductility test gives a measure of the adhesive property of bitumen and its ability to stretch. In flexible pavement design, it is necessary that binder should form a thin ductile film around aggregates so that the physical interlocking of the aggregates is improved. Binder material having insufficient ductility gets cracked when subjected to repeated traffic loads and it provides a pervious pavement surface. The ductility of a bituminous material is measured by the distance in centimetres to which it will elongate before breaking when two ends of a standard briquette specimen of material are pulled apart at a specified speed and a specified temperature.

Ductility:

The ductility is expressed as a distance in cm to which a standard briquette of bitumen can be stretched before the thread breaks.

Ductility value:

The distance stretched by the moving end of the specimen up to the point of breaking of the thread measured in cm is recorded as ductility value.

PROCEDURE:

1. Melt the bituminous test material completely at a temperature of 75°C to 100 °C above the approximate softening point until it becomes thoroughly fluid.
   
2. Strain the fluid through IS sieve 30.
   
3. After stirring the fluid, pour it into the mould assembly and place it on a brass plate. In order to prevent the material under test from sticking, coat the surface of the plate and interior surfaces of the sides of the mould with mercury or a mixture of equal parts of glycerin and dextrin.
   
4. After about 30-40 minutes, keep the plate assembly along with the sample in a water bath.
   
5. Maintain the temperature of the water bath at 27° C for half an hour.
   
6. Remove the sample and mould assembly from the water bath and trim the specimen by levelling the surface using a hot knife.
   
7. Replace the mould assembly in a water bath for 80 to 90 minutes.
   
8. Remove the sides of the mould.
   
9. Hook the clips carefully on the machine without causing any initial strain. Adjust the pointer to read zero.
   
10. Start the machine and pull clips horizontally at a speed of 50 mm per minute.
    
11. Note the distance at which the bitumen thread breaks.
    

The mean of two observations rounded to the nearest whole number is the ductility value.

Note:Themachine may have a provision to fix two or more moulds so as to test three specimens simultaneously.

OBSERVATIONS:

• • Bitumen Grade =
    
  • Pouring Temperature =
    
  • Test Temperature =
    
  • Period of cooling in minutes =
    
• In air =
  
• In water bath before trimming =
  
• In water bath after trimming =
  

Briquette MouldDuctility Machine

RESULT: