Test On Bitumen

LAB TESTS ON BITUMEN TO CHECK QUALITY

Various tests are conducted on bitumen to assess its consistency, gradation, viscosity, temperature susceptibility, and safety.

There are a number of tests to assess the properties of bituminous materials. The following tests are usually conducted to evaluate different properties of bituminous materials.

1.Penetration test ,

2.Ductility test

3.Softening point test

4.Specific gravity test

5.Viscosity test

6.Flash and Fire point test

7.Float test

8.Loss on heating test

1.PENETRATION TEST

It is done to find out the grade of the bitumen.It measures the hardness or softness of bitumen by measuring the depth in tenths of a millimeter to which a standard loaded needle will penetrate vertically in 5 seconds. BIS had standardized the equipment and test procedure.

The penetrometer consists of a needle assembly with a total weight of 100g and a device for releasing and locking in any position. The bitumen is softened to a pouring consistency, stirred thoroughly and poured into containers at a depth at least 15 mm in excess of the expected penetration. The test should be conducted at a specified temperature of 250C+-0.1.

It may be noted that penetration value is largely influenced by any inaccuracy with regards to pouring temperature, size of the needle, weight placed on the needle and the test temperature.

In hot climates, a lower penetration grade is preferred. The Fig-1 shows a schematic Penetration Test setup.     

2.DUCTILITY TEST

Ductility is the property of bitumen that permits it to undergo great deformation or elongation. Ductility is defined as the distance in cm, to which a standard sample or briquette of the material will be elongated without breaking. Dimension of the briquette thus formed is exactly 1 cm square. The bitumen sample is heated and poured in the mould assembly placed on a plate. These samples with moulds are cooled in the air and then in water bath at 270C temperature. The excess bitumen is cut and the surface is leveled using a hot knife. Then the mould with assembly containing sample is kept in water bath of the ductility machine for about 90 minutes. The sides of the moulds are removed, the clips are hooked on the machine and the machine is operated. The distance up to the point of breaking of thread is the ductility value which is reported in cm.

The ductility value gets affected by factors such as pouring temperature, test temperature, rate of pulling etc.

A minimum ductility value of 75 cm has been specified by the BIS. Fig-2 shows ductility Test Process.

                                               SOFTENING POINT TEST OF BITUMEN (IS 1205-1978)

DEFINITION

Softening point is the temperature at which the substance attains a particular degree of softening under specified conditions of test.

 APPARATUS 

 Standard Ring and Ball Apparatus. 

 Steel balls 2 No, each 9.5mm in diameter and weighing 3.5 + 0.05 grams. 

 Brass rings 2 No, the rings shall be tampered and shall confirm to the following Depth : 6.4 + 0.1mm Inside diameter at bottom : 15.9 + 0.1mm Inside diameter at top : 17.5 + 0.1mm Outside diameter : 20.6 + 0.1mm 

 Thermometer capable of reading temperature up to 0 to 250 0 C. 

 Water bath should be a heat resistant glass vessel not less than 85mm in diameter and 120mm in depth. 

 Stirrer shall be manual or mechanical to ensure uniform heat distribution at all times throughout the water bath.

 PROCEDURE 

 Heat the material to a temperature between 75 to 100 0 C above its softening point. 

 Stir until it is completely fluid and free from air bubbles and water, and filter if necessary, through IS sieve 30. 

 Place the rings, previously heated to a temperature approximately to that of molten material on a metal plate, which has been coated with a mixture of equal parts of glycerin and dextrin. 

 Fill the mould with sufficient melt to give excess above the level of the ring. 

 Remove the excess material with a warmed sharp knife after cooling in air for 30 minutes. 

 Assemble the apparatus with the rings, thermometer and ball guides in position 

 Fill the bath to a height of 50mm above the upper surface of the rings with the freshly boiled distilled water or pure glycerin at a temperature of 5 0 C. 

 The water bath liquid shall be freshly boiled distilled water when testing materials having softening points below 80 0 C and pure glycerin for material having softening points above 80 0 C.  There shall be exactly 25mm difference between the bottom of the rings and the top surface of the bottom plate of the support, if any, or the bottom of the bath. 

 Maintain the bath at a temperature of 5 0 C for 15 minutes after which place the balls previously cooled to a temperature of 5 0 C by forceps in each ball guide. 

 Apply heat to the bath and stir the liquid so that the temperature rises at a uniform rate of 5 + 0.5 0 C per minute until the material softens and allow the balls to pass through the ring. 

 Record the temperature shown by the thermometer for each ring and ball at the instant the sample surrounding the ball touches the bottom plate of the support, if any or the bottom of the bath. Softening point test for bitumen.

 REPORT

 Report to the nearest 0.5 0 C the mean of the temperature recorded in duplicate as the softening point. 

PRECISION 

 Test results shall not differ from the mean by the following 

Softening Point                       Repeatability                       Reproducibility 

 40 to 60                                         1.00                                      5.50                                                             

 61 to 80                                          1.50                                     5.50                                                             

 81 to 100                                        2.00                                     5.50                                                       

 101 to 120                                      2.50                                     5.50                                                             

 121 to 140                                      3.00                                     5.50        

                                       

   PRECAUTIONS 

 The stirrer shall be so placed that the moulds are not disturbed when the stirrer is in operation. 

 The prescribed rate of heating shall be rigidly adhered to for ensuring accuracy of results. 

 The rate of temperature rise shall not be averaged over the period of the test. 

   SPECIFIC GRAVITY TEST ON BITUMEN(IS 1202-1978)

INTRODUCTION

Specific gravity is defined as 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.

APPARATUS

• Specific gravity bottle of 50 ml capacity, ordinary capillary type with 6 mm diameter neck or wide mouthed capillary type bottle with 25 mm diameter neck
• Balance having least count of 1g

PROCEDURE

1. The specific gravity bottle is cleaned, dried and weighed along with the stopper.
2. It is filled with fresh distilled water, stopper placed and the same is kept in water container for at least half an hour at temperature 270C.
3. The bottle is then removed and cleaned from outside. The specific gravity bottle containing distilled water is now weighed.
4. The bituminous material is heated to a pouring temperature and is poured in the above empty bottle taking all the precautions that it is clean and dry before filling sample materials. The material is filled up to the half taking care to prevent entry of air bubbles.
5. To permit an escape of air bubbles, the sample bottle is allowed to stand for half an hour at suitable temperature cooled to 270C and then weighed.
6. The remaining space in the specific gravity bottle is filled with distilled water at 270C , stopper placed and is placed in water container at 270C.
7. The bottle containing bituminous material and containing water is removed, cleaned from outside and is again weighed.

CALCULATION

The specific gravity of the material is calculated as follows:

Specific gravity = weight of bituminous material/weight of equal volume of water

= (c-a)/[(b-a)-(d-c)]

Where,

a = weight of specific gravity bottle, g

b = weight of specific gravity bottle filled with distilled water, g

c = weight of the specific gravity bottle about half filled with bituminous material, g

d = weight of the specific gravity bottle about half filled with material and the rest with distilled water, g

RESULTS

At least three measurements should be made for determining value of the specific gravity

PRECAUTIONS

• It is necessary that all precautions are taken in making the specific gravity bottles thoroughly cleaned and dried in the first weighting.
• The surface of the specific gravity bottle should be cleaned dry after filling with water, before weighing.
• The test temperature should be firmly adhered to.
• Inaccurate balance would never give reproducible results.

    VISCOSITY TEST OF BITUMEN (IS 1206-PART-2)

ABSOLUTE VISCOSITY TEST OF BITUMEN

REFERENCE

IS: 1206 (Part 2) – Method for Testing Tar and Bitumen Materials: Determination of Absolute Viscosity

TEST EQUIPMENT

The following testing equipment is needed to measure absolute viscosity of viscosity graded paving bitumen (IS:73-2006) at 60 C in accordance with IS:1206 (Part 2) (similar to ASTM D 2171), which uses a vacuum capillary viscometer. It should be noted that any other viscometer such as rotational viscometer cannot be used to measure the absolute viscosity at 60 C since the bitumen in non Newtonian in nature at this temperature.

While obtaining quotations specify the following requirements. Although Asphalt Institute vacuum viscometer and Modified Koppers vacuum viscometer can also be used, the following refers to Cannon-Manning vacuum viscometer only.

Complete Absolute Viscosity Testing Equipment conforming to IS:1206 (Part 2) Method for Testing Tar and Bitumen Materials: Determination of Absolute Viscosity with the following components:

1. Constant Temperature Bath – A suitable bath for immersion of at least 6 vacuum capillary viscometer tubes with a digital temperature controller. The accuracy of the temperature in the bath should be +/- 0.1 C throughout the bath.
2. Silicone Bath Oil suitable up to 150 C
3. Vacuum System – Capable of maintaining a vacuum within +/- 0.05 cm of the desired level up to and including 30 cm of mercury. The system shall consist of vacuum pump, moisture trap, vacuum regulator, manometer with electronic controller, bleed valve, all interconnecting tubing/piping, and any other accessories as needed to complete the vacuum system.
4. Thermometer for Bath – Mercury in glass, range 37.8 to 82 C, and graduations of 0.2 C.
5. Timing Device – A stop watch or stop clock capable of reading up to ½ second.

   

   Pic-1 Viscosity test of bitumen

6. Cannon-Manning Vacuum Viscometers– With manufacturers’ calibration certificate, viscometer holder and silicone cork. Size 12 and Size 13 (one each) [Size 12 is suitable for testing VG-10 and Size 13 is suitable for testing VG-20, VG-30, and VG-40 bitumen.]
7. Viscometer Stand – for holding 6 viscometers.
8. Installation of the quoted instrument in client’s laboratory and operational training.

Note: Only the Cannon-Manning viscometer tubes need to be imported at this time, the remaining equipment such as bath and vacuum system are available in India.

Pic-2 Viscosity test of bitumen

However, be aware of water bath and vacuum control systems manufactured in India, many do not give the accuracy and consistency needed for the test (viscosity is very sensitive to small variations in temperature and vacuum level). Try them out carefully before buying them. If not satisfactory, these systems may have to be imported.

TEST PROCEDURE

PREPARATION OF SAMPLE:

Pic-3 Viscosity test of bitumen

1. Heat the bitumen sample to a temperature not more than 90 C above its approx. softening point until is has become sufficiently fluid (like motor oil) to pour easily (Pic-1).
2. Transfer about 20 ml into a suitable container (Pic-2) and maintain at a temperature of 135 +/- 5.5 C stirring occasionally to allow entrapped air to escape.
3. Pour the hot bitumen in the Canning-Manning vacuum viscometer through the larger diameter filling tube A so that bitumen is within +/- 2 mm of the fill line E. Place the charged viscometer in an oven or bath maintained at 135 +/- 5.5 C for a period of 10 +/- 2 minutes to allow larger air bubbles to escape.

   

   Pic-4 Viscosity test of bitumen

TESTING:

1. Maintain the test bath temperature at 60 +/- 0.1 C. Place the charged viscometer vertically in the test bath with the help of a holder so that that the uppermost timing mark is at least 2 cm below the surface of the bath liquid (Pic-3).
2. Establish a vacuum of 30 +/- 0.05 cm of mercury in the vacuum system and connect to the viscometer with the valve closed. After the viscometer has been in the bath for 30 +/- 5 min, open the valve and allow the bitumen to flow in the viscometer.

   

   Pic-5 Viscosity test of bitumen

3. Measure the time required (to within +/- 0.5 sec) for the leading edge of the meniscus to pass between successive pairs of timing marks (Pic-4 and 5).
4. Report the first flow time which exceeds 60 sec between a pair of timing marks, noting the identification of the pair of the timing marks.

CALCULATION:

Calculate (Pic-6) and report the absolute viscosity in poises to three significant figures as follows:

Pic-6 Viscosity test of bitumen

Viscosity in poises = K t

Where:

K = Calibration factor in poise per second supplied with the viscometer tube for the pair of timing marks where the flow time exceeded 60 seconds.

t = flow time in seconds

REPORT:

Report the test temperature and vacuum level with the viscosity test results such as viscosity in poises @ 60 C and 300 mm mercury vacuum.

                                           FLASH & FIRE POINT OF BITUMEN

This test is done to determine the flash point and the fire point of asphaltic bitumen and fluxed native asphalt, cutback bitumen and blown type bitumen as per IS: 1209 – 1978. The principle behind this test is given below

Flash Point – The flash point of a material is the lowest temperature at which the application of test flame causes the vapours from the material to momentarily catch fire in the form of a flash under specified conditions of the test.

Fire Point – The fire point is the lowest temperature at which the application of test flame causes the material to ignite and burn at least for 5 seconds under specified conditions of the test.

The apparatus required for this test is
i) Pensky-Martens apparatus
ii) Thermometer- Low Range : -7 to 110^oC, Graduation 0.5^oC
High Range : 90 to 370^oC, Graduation 2^oC

The sample should be just sufficient to fill the cup upto the mark given on it.

Procedure to determine the Flash And Fire Point Of Bitumen

A) FLASH POINT

i) Soften the bitumen between 75 and 100^oC. Stir it thoroughly to remove air bubbles and water.

ii) Fill the cup with the material to be tested upto the filling mark. Place it on the bath. Fix the open clip. Insert the thermometer of high or low range as per requirement and also the stirrer, to stir it.

iii) Light the test flame, adjust it. Supply heat at such a rate that the temperature increase, recorded by the thermometer is neither less than 5^oC nor more than 6^oC per minute.

iv) Open flash point is taken as that temperature when a flash first appears at any point on the surface of the material in the cup. Take care that the bluish halo that sometimes surrounds the test flame is not confused with the true flash. Discontinue the stirring during the application of the test
flame.

v) Flash point should be taken as the temperature read on the thermometer at the time the flash occurs.

                                                                FLOAT TEST 

SCOPE 

 Description of Test :

 The Float Test is used as a measure of consistency for distillation residues. Residue from the emulsion is cast in a tapered collar, and then it is allowed to float in a testing bath at a specified temperature. The time, in seconds, between placing the apparatus on the water and the water breaking through the material shall be taken as a measure of the consistency of the material under examination. 

APPARATUS AND MATERIALS 

 equipment including float and thimble as described in ASTM D139, Section 5.

 Coat the brass plate with a 1:100 mixture of Versamid and Castor Oil. Water bath at 60o 0.5o C. 

Ice bath. 

Spatula.

 Thermometer, ASTM No. 20C (57o C to 65o C), length 275 mm. 

Watch or clock with a second hand. 

PROCEDURE 

1. Pour the sample immediately after completion of distillation into a suitable preheated container and then into the float thimble

2.Place the thimble threaded side down, on the coated brass plate.

3.Fill the thimble with asphalt until slightly more than level with the top.

4. Allow the asphalt to cool to room temperature for 30 minutes.

5. Place the plate and thimble in the ice bath for 5 minutes. 

6.Trim the material flush to the top of the thimble with a slightly heated spatula.

7.Place again in the ice bath for a period of 30 minutes.

8.Screw the thimble onto the float and immerse the entire assembly in the ice bath for 1 minute. 

9.Take the assembly out of hte ice bath and float it on the water bath heated to 60o C. 

10.Measure the time in seconds from the instant the float is put on the water bath until the water breaks the material and enters the float.

Note:The float value is one of the prime characteristics for identifying "high float" asphalt emulsions. This high float characteristics enables softer asphalt materials to remain in place on the roadway without running off. 

References : ASTM D139, Volume 04.03 ASTM D244, Section 66, Volume 04.03 N.S.C. CAN 2-16.5-M84, Par. 6.2.6