OBJECT: TO DETERMINE PENETRATION VALUE (GRADE) AND SOFTENING POINT OF BITUMEN

PENETRATION TEST OF BITUMEN

(AASHTO T-49, ASTM D-5)

PERFORMANCE OBJECTIVE:

Upon successful completion of this lab experiment, the student will able to:

• To determine the consistency of bituminous material
  
• To assess the suitability of bitumen for use under different climatic conditions and various types of construction.
  
• To classify the bitumen into different grades.
  

EQUIPMENTS:

1) Needle 2) Water Bath 3) Penetrometer

DISCUSSION:

Penetration test is the most commonly adopted test on bitumen to grade the material in terms of its hardness. Depending upon the climatic condition and type of construction, bitumen of different penetration grades are used. For example, 80/100 bitumen denotes that the penetration value ranges between 80 and 100. For bituminous macadam and penetration macadam bitumen grades 30/40, 60/70 and 80/100 are used. In warmer regions lower penetration grades are preferred and in colder regions bitumen with higher penetration values is used.

PROCEDURE:

1. Soften the bitumen to a pouring consistency between 75⁰C and 100⁰C above the approximate temperature at which bitumen softens.
   

1. Stirrer the sample material thoroughly stirred to make it homogenous and free from air bubbles and water.
   

1. Pour the sample material into the container at a depth of at least 15 mm or more than the expected penetration.
   

1. Cool the sample containers in an atmosphere of a temperature of not lower than 13⁰C for one hour.
   

1. Then place them in temperature temperature-controlled water bath at a temperature of 25⁰C for one hour.
   

1. Place the sample container in the transfer tray with water from the water bath and place it under the needle of the penetrometer.
   

1. 
   Check the weight of the needle, shaft, and additional weights. The total weight of this assembly should be 100g.
   

1. 
   By using the adjusting screw, lower the needle assembly as the tip of the needle just touches the top surface of the sample, the needle assembly is clamped in this position.
   

1. 
   Either the initial reading of the penetrometer dial is either adjusted to zero or the initial reading is taken before releasing the needle.
   

NOTE: The needle is released exactly for a period of 5.0 seconds by pressing the knob and the final reading is taken on the dial.

1. Take three measurements on this sample by testing at distances of not less than 100 mm apart.
   

1. After each test, disengage the needle and clean it with benzene, and dry it carefully.
   

1. Before the next testing, transfer the sample container to the water bath to maintain a constant temperature of 25⁰C.
   

NOTE: The penetration test is not used to estimate the consistency of the softer materials like cutback or tar, which are usually graded by a viscosity test in an orifice viscometer.

HIGIIWAYS ENGINEERING LABORATORY OBSERVATION SHEET

PENETRATION TEST

RESULT:

COMMENTS:

SOFTENING POINT TEST

(AASHTO T-53, ASTM D-36)

PERFORMANCE OBJECTIVE:

Upon successful completion of this lab experiment, the student will able to:

• To determine the temperature at which the bituminous binders have an equal viscosity.
  
• Classify the bitumen for different regions for example bitumen with a higher softening point may be referred to in warmer regions.
  

EQUIPMENT:

1. Steel balls having a diameter of 9.5mm and weight of 3.5 ± 0.05g
   

1. 
   
   Brass rings of the following dimensions,
   

Depth ————– 6.4mm,

Inside Diameter at Top —————- 7.5mm

Inside diameter at Bottom ———— 15.9 mm

Outside diameter ————- 20.6mm

1. A metallic supports is used for placing pair of rings.
   

1. A heat resistant glass beaker of 85mm diameter and 120 mm depth is used.
   

1. A temperature controlled heating plate.
   

1. Thermometer
   

DISCUSSION:

Softening point is the temperature at which the substance attains particular degree of softening under specified condition of test. Bitumen does not melt, but as the temperature increases, it changes gradually from solid to liquid.

For determining softening point Ring and Ball apparatus is used for the test.

It is a fact that harder bitumen possesses higher softening point than softer bitumen.

PROCEDURE:

1. Heat the sample material to a temperature between 75⁰C and 100⁰C above the approximate softening point until it is completely fluid and is poured in heated rings placed on metal plate.

1. Do the coating to the plate with the solution of glycerine, to avoid sticking of the bitumen to the metal plate.
   
2. Cool rings for 30 minutes in air.
   
3. Then trim the excess bitumen and place the rings on support. Keep the temperature of distilled water at 5⁰C, and maintain this temperature for 15 minutes after balls are placed in position
   
4. Raise the temperature of the water at a uniform rate of 5⁰C per minute with a controlled heating unit, until the bitumen softens and touches the bottom of the plate by sinking of balls. Make at least two observations.
   

APPLICATIONS:

Softening point essentially is the temperature at which the bituminous binders have an equal Viscosity. Bitumen with higher softening point may be referred in warmer place. Softening point is also sometimes used to specify hard bitumen.

HIGIIWAYS ENGINEERING LABORATORY OBSERVATION SHEET

SOFTENING POINT TEST

RESULT & COMMENTS: