Determination of Softening point of bitumen

Softening point of bitumen (IS 1205:1978)

Softening point of bitumen is that temperature at which it attains some degree of softness.The test is conducted by using Ring and Ball apparatus. A brass ring containing test sample of bitumen is suspended in liquid like water or glycerin at a given temperature. A steel ball is placed.upon the bitumen sample and the liquid medium is heated at a rate of 5⁰C per minute. Temperature is noted when the softened bitumen touches the metal plate which is at a specified distance below. Generally, higher softening point indicates lower temperature susceptibility and is preferred in hot climates.

 Apparatus

Ring and ball apparatus with all components, Thermometer, heating apparatus, Bath and stirrer.

Softening point apparatus

 

 

 

Procedure

1. Sample of bitumen is heated to a temperature between 75° and 100°C above the approximate softening point until it is completely fluid and is poured in heated rings placed on the metal plate.
2. To avoid sticking of the bitumen to metal plate, coating is done to this with a solution of glycerin.
3. After cooling the rings in air for 30 minutes, the excess bitumen is trimmed and rings are placed in the support.
4. At this time the temperature of distilled water is kept at 5°C. This temperature is maintained for 15 minutes after which the balls are placed in position.
5. Then the temperature of water is raised at uniform rate of 5°C per minute with a controlled heating unit, until the bitumen softens and touches the bottom plate by sinking of balls. At least two observations are made. For material whose softening point is above 80°C, glycerin is used for heating medium and the starting temperature is 35°C instead of 5°C.

Observations

Softening point of bitumen varying from 35 degree Celsius to 70 degree Celsius are used for various paving zones.Bitumen with higher temperature susceptibility or lower softening points are used in colder regions and vice versa.

 

Penetration test on bitumen

Penetration test on bitumen

Penetration on bitumen is conducted to classify the bitumen in different grades.This tests determine the consistency of bitumen for the purpose of grading by measuring the depth of standard needle penetrating the bitumen sample vertically under specific conditions of load, temperature time.

Apparatus

A flat bottomed cylindrical metallic dish 55mm in diameter and 35 mm in depth is required. If the penetration is of the order of 225 or more, dish of 70mm diameter and 45mm depth is required, Water bath maintained at 25 degree Celsius, Penetration apparatus: Should be such that it allows needle to penetrate without much friction & is accurately calibrated to give results in one tenth of a millimeter, Time measuring device with an accuracy of a second.

Penetrometer

Procedure

1. Soften the material to a pouring consistency at a temperature not more than 60 degree Celsius for tars and 90 degree Celsius for bitumen above the approximate softening point and stir it thoroughly until it is homogeneous and is free from air bubbles and water.
2. Pour the melt into the container to a depth at least 10 mm in excess of the expected penetration. Protect the sample from dust and allow it to cool in an atmosphere at a temperature between 15degree Celsius to 30 degree Celsius for one hour. Then place it along with the transfer dish in the water bath at 25 degree Celsius.
3. Fill the transfer dish with water from the water bath to depth sufficient to cover the container completely, place the sample in it and put it upon the stand of the penetration apparatus.Clean the needle with benzene, dry it and load with the weight. The total moving load required is 100 grams, including the weight of the needle, carrier and super-imposed weights. 
4. Adjust the needle to make contact with the surface of the sample. This may be done by placing the needlepoint in contact with its image reflected by the surface of the bituminous material.
5. Make the pointer of the dial to read zero or note the initial dial reading.Release the needle for exactly five seconds.Adjust the penetration machine to measure the distance penetrated
6. Make at least 3 readings at points on the surface of the sample not less than 10 mm apart and not less than l0mm from the side of the dish. After each test return the sample and transfer dish to the water bath and wash the needle clean with benzene and dry it. In case of material of penetration greater than 225, three determinations on each of the two identical test specimens using a separate needle for each determination should be made, leaving the needle in the sample on completion of each determination to avoid disturbance of the specimen.

Observations

Penetration test is generally used to determine the hardness of bitumen because of its simplicity.Softer the bitumen more will be its penetration value.For example 80/100 bitumen grade denotes the bitumen sample having penetration value between 8 mm to 10 mm.

 

Conducting Soundness test on Aggregates

Soundness test on Aggregates (IS 2386 Part 5 )

Soundness of aggregates is the resistance possessed by the aggregates against the weathering agencies.To quicken this weathering action due to alternate wetting and drying and freezing thawing saturated solution of sodium sulphate or magnesium sulphate are used.

Apparatus

Sample, Weighing balance up to capacity 500 g (Least count 0.1 g), Weighing balance up to capacity 5000 g (Least count 1 g), Oven, Sieves, 80 mm, 63 mm, 40 mm, 31.5 mm, 25 mm, 20 mm, 16 mm, 12.5 mm, 10 mm, 8.0 mm, 4.75 mm, 4.0 mm, 2.36 mm, 1.18 mm, 600 micron, 300 micron, 150 micron, Chemicals Sodium sulphate or magnesium sulphate, Wire mesh bucket, Container

Sample preparation for fine aggregates

1. Make a sieve set with sieves as per the table starting from 10 mm to 300 micron.
2. The amount of sample to be taken for sieving is such that, it will yield not less than 100 g of each of the following sizes.
3. Weigh 100 g of sample from each of the separated fraction and place it in separate containers for the test. 

   

   Sieve set for fine aggregates

 Sample preparation for coarse aggregates

1. 1.Sieve the washed aggregates through 4.75 mm sieve and take the coarse aggregates retained over the sieve.
   2. Sieve the sample through 80,63,40,20,10,4.75  mm sieve and get the yield as per the table given below.
   3.Take the weight and put the sample in individual separate containers.

   

   Sieve set and Yield limits for Coarse aggregates

   
   

   Procedure

   1. 1. Take the individual samples of aggregates and put them in solution of sodium sulphate or magnesium sulphate for about 17 hours in such a way that solution is 15 mm above the aggregates.
      2. Now dry the aggregates and puth them in oven until they obtain constant weight.
      3. Now cool down the aggregates and repeat the first step.
      4. Number of such cycles are decided by the seller and vendor agreement.
      5. After completion of these cycles the aggregates are washed from sodium sulphate solution.And this can be tested by the reaction of the wash water with barium chloride.
      6. Now dry the aggregates and put in oven till they get a constant weight.
      7. After that cool down the aggregates and sieve the fine aggregates on same sieve on which they retained before the test.
      8.  sieve the coarse aggregates on the sieves shown in table below.
      
      

      

      Sieves used to determine loss

       Note:-

      Average weight loss should not exceed 12 percent when tested with 10 cycles of sodium sulphate  and 18 percent  when tested with magnesium sulphate.

      
      
   
   

Determining Flakiness Index of Aggregates

  Flakiness Index of Aggregates (IS:2386 part 1)

Aggregate particles are classified as flaky when they have a thickness (smallest dimension) of less than 0.6 of their mean sieve size. The flakiness index of an aggregate sample is found by separating the flaky particles and expressing their mass as a percentage of the mass of the sample tested. This test is not applicable to aggregate passing 6.30mm sieve and retained as 63.0mm sieve. Flaky particles are considered to be unsuitable for the pavement materials. Flaky particles tends to get broken as the impact loading of vehicles passing over the road.

Apparatus

Sample,Weighing machine, Thickness gauge,Is Sieves of sizes 63mm, 50mm, 40mm, 31.5mm, 25mm, 20mm, 16mm, 10mm and 6.3mm.

Thickness Gauge

Test Procedure

1. Take the aggregate sample having at least 200 pieces of different sized aggregates.
2. Sieve the sample through mentioned sieves i.e., from 63mm to 6.3mm sieves.
3. Aggregates retained on 63 mm and passing 6.3mm are discarded.
4. Now weigh aggregate retained on different sieve and note down the total weight as “W1”
5. The aggregate particles from each of the size range is taken and passed through corresponding gauge of thickness gauge or flakiness gauge with its thinnest side facing the slot thickness  of gauge.
6. Each gauge length is 0.6 times the mean dimension of aggregate size range. If particle retained on 16mm and passed through 20mm size is taken, then it should pass through 10.8 mm slot of gauge which is 0.6 times the mean of 16mm and 20 mm.(i.e. [{0.6*(16+20)}/2]=10.8 mm
7. The particles that were passing through the length gauge are weighed which is “W2”.
8. Now calculate the flakiness index which is the ratio of weight of particles passed through thickness gauge to the total weight of the sample gauged and it is expressed in percentage.

Calculations:

Elongation index =(W2/W1) X 100

W1= Weight passed of aggregates through thickness gauge
W2= Total sample weight.
Flakiness Index should not more than 15 %  for pavement aggregates material.

Determination of Elongation Index of Aggregates

Elongation Index of Aggregates (IS:2386 part 1)

The elongation index of an aggregate is the percentage by weight of particles whose greatest dimension ( length ) is greater than 1.8 times their mean dimension.For this test aggregates passing 63 mm and retaining at 6.3 mm are taken.The elongation test is not applicable to sizes smaller than 6.3 mm. Elongated particles are considered unsuitable for the pavement. Elongated particles get broken when loaded vehicles pass over the pavement leading weakness of the structure.These particles also create problem in close packing of the aggregates leading to voids in concrete.

Apparatus

Sample,Weighing machine, Length gauge,Is Sieves of sizes 63mm, 50mm, 40mm, 31.5mm, 25mm, 20mm, 16mm, 10mm and 6.3mm.

Length Gauge

Test Procedure

1. Take the aggregate sample having at least 200 pieces of different sized aggregates.
2. Sieve the sample through mentioned sieves i.e., from 63mm to 6.3mm sieves.
3. Aggregates retained on 63 mm and passing 6.3mm are discarded.
4. Now weigh aggregate retained on different sieve and note down the total weight as “W1”
5. The aggregate particles from each of the size range is taken and passed through corresponding gauge of length gauge or elongation gauge with its longest side facing the width of gauge.
6. Each gauge length is 1.8 times the mean dimension of aggregate size range. If particle retained on 16mm and passed through 20mm size is taken, then it should pass through 32.4mm length gauge which is 1.8 times the mean of 16mm and 20 mm.(i.e. [{1.8*(16+20)}/2]=32.4 mm
7. The particles that were retained on the length gauge are weighed which is “W2”.
8. Now calculate the elongation index which is the ratio of weight of particle retained on length gauge to the total weight of the sample gauged and it is expressed in percentage.

Calculations:

Elongation index =(W2/W1) X 100

W1= Weight retained of aggregates on length gauge
W2= Total sample weight.
Elongation Index should not more than 15 %  for pavement aggregates material.