This test is done to determine the penetration of bitumen as per IS: 1203 – 1978. The principle is that the penetration of a bituminous material is the distance in tenths of a mm, that a standard needle would penetrate vertically, into a sample of the material under standard conditions of temperature, load and time. The apparatus needed to determine the penetration of bitumen is

i) Penetrometer

ii) Water bath

iii) Bath thermometer – Range 0 to 44^oC, Graduation 0.2^oC

SAMPLE
Bitumen should be just sufficient to fill the container to a depth of at least 15mm in excess of the expected penetration.

Procedure to determine the penetration of bitumen
i) Soften the bitumen above the softening point (between 75 and 100^oC). Stir it thoroughly to remove air bubbles and water.

ii) Pour it into a container to a depth of at least 15mm in excess of the expected penetration.

iii) Cool it at an atmospheric temperature of 15 to 30^oC for 1^1/2 hours. Then place it in a transfer dish in the water bath at 25.0 + 0.1^oC for 1^1/2 hrs.

iv) Keep the container on the stand of the penetration apparatus.

v) Adjust the needle to make contact with the surface of the sample.

vi) Adjust the dial reading to zero.

vii) With the help of the timer, release the needle for exactly 5 seconds.

viii) Record the dial reading.

ix) Repeat the above procedure thrice.

REPORTING OF RESULTS
The value of penetration reported should be the mean of not less than three determinations expressed in tenths of a mm.

This test is done to determine the Marshall stability of bituminous mixture as per ASTM D 1559. The principle of this test is that Marshall stability is the resistance to plastic flow of cylindrical specimens of a bituminous mixture loaded on the lateral surface. It is the load carrying capacity of the mix at 60oC and is measured in kg. The apparatus needed to determine Marshall stability of bituminous mixture is

i) Marshall stability apparatus
ii) Balance and water bath

The sample needed is
From Marshall stability graph, select proportions of coarse aggregates, fine aggregates and filler in such a way, so as to fulfill the required specification. The total weight of the mix should be 1200g.

Procedure to determine Marshall stability of bituminous mixture
i) Heat the weighed aggregates and the bitumen separately upto 170^oC and 163^oC respectively.

ii) Mix them thoroughly, transfer the mixed material to the compaction mould arranged on the compaction pedestal.

iii) Give 75 blows on the top side of the specimen mix with a standard hammer (45cm, 4.86kg). Reverse the specimen and give 75 blows again. Take the mould with the specimen and cool it for a few minutes.

iv) Remove the specimen from the mould by gentle pushing. Mark the specimen and cure it at room temperature, overnight.

v) A series of specimens are prepared by a similar method with varying quantities of bitumen content, with an increment of 0.5% (3 specimens) or 1 bitumen content.

vi) Before testing of the mould, keep the mould in the water bath having a temperature of 60^oC for half an hour.

vii) Check the stability of the mould on the Marshall stability apparatus.

REPORTING OF RESULTS
Plot % of bitumen content on the X-axis and stability in kg on the Y-axis to get maximum Marshall stability of the bitumen mix. A sample plot is given

This test is done to determine the specific gravity of semi-solid bitumen road tars, creosote and anthracene oil as per IS: 1202 – 1978. The principle is that it is the ratio of mass of a given volume of bitumen to the mass of an equal volume of water, both taken at a recorded/specified temperature.
The apparatus needed to determine specific gravity of bitumen is

i) Specific gravity bottles of 50ml capacity
ii) Water bath
iii) Bath thermometer – Range 0 to 44^oC, Graduation 0.2^oC
Take the sample (half the volume of the specific gravity bottles).

Procedure to determine specific gravity of bitumen
i) Clean, dry and weigh the specific gravity bottle along with the stopper (Weight ‘A’).

ii) Fill the specific gravity bottle with freshly boiled distilled water and insert the stopper firmly. Keep it in the water bath having a temperature of 27.0 + 1^oC for not less than half an hour and weigh it (Weight ‘B’).

iii) Weigh the specific gravity bottle about half-filled with the material (Weight ‘C’).

iv) Weigh the specific gravity bottle about half-filled with the material and the other half with distilled water (Weight ‘D’).

v) Weigh the specific gravity bottle completely filled with the material (Weight ‘E’).

REPORTING OF RESULTS
i) Specific gravity (Solids and semi-solids) = (C-A )/[ ( B-A) - (D-C)]
ii) Specific gravity (Liquids) = (E-A)/(B-A)
The average of the two results should be reported.

BITUMEN CONTENT
This test is done to determine the bitumen content as per ASTM 2172. The apparatus needed to determine bitumen content are -
i) Centrifuge extractor
ii) Miscellaneous – bowl, filter paper, balance and commercial benzene.
A sample of 500g is taken.

Procedure to determine bitumen content
i) If the mixture is not soft enough to separate with a trowel,place 1000g of it in a large pan and warm upto 100^oC to separate the particles of the mixture uniformly.

ii) Place the sample (Weight ‘A’) in the centrifuge extractor. Cover the sample with benzene, put the filter paper on it with the cover plate tightly fitted on the bowl.

iii) Start the centrifuge extractor, revolving slowly and gradually increase the speed until the solvent ceases to flow from the outlet.

iv) Allow the centrifuge extractor to stop. Add 200ml benzene and repeat the procedure.

v) Repeat the procedure at least thrice, so that the extract is clear and not darker than the light straw colour and record the volume of total extract in the graduated vessel.

vi) Remove the filter paper from the bowl and dry in the oven at 110 + 5^oC. After 24hours, take the weight of the extracted sample (Weight ‘B’).

REPORTING OF RESULTS
Bitumen content = [(A-B)/B]×100 %
Repeat the test thrice and average the results.

ULTRASONIC PULSE VELOCITY

This test is done to assess the quality of concrete by ultrasonic pulse velocity method as per IS: 13311 (Part 1) – 1992. The underlying principle of this test is -
The method consists of measuring the time of travel of an ultrasonic pulse passing through the concrete being tested. Comparatively higher velocity is obtained when concrete quality is good in terms of density, uniformity, homogeneity etc.
Procedure to determine strength of hardened concrete by Ultrasonic Pulse Velocity.
i) Preparing for use: Before switching on the ‘V’ meter, the transducers should be connected to the sockets marked “TRAN” and ” REC”.
The ‘V’ meter may be operated with either:
a) the internal battery,
b) an external battery or
c) the A.C line.

ii) Set reference: A reference bar is provided to check the instrument zero. The pulse time for the bar is engraved on it. Apply a smear of grease to the transducer faces before placing it on the opposite ends of the bar. Adjust the ‘SET REF’ control until the reference bar transit time is obtained on the instrument read-out.

iii) Range selection: For maximum accuracy, it is recommended that the 0.1 microsecond range be selected for path length upto 400mm.

iv) Pulse velocity: Having determined the most suitable test points on the material to be tested, make careful measurement of the path length ‘L’. Apply couplant to the surfaces of the transducers and press it hard onto the surface of the material. Do not move the transducers while a reading is being taken, as this can generate noise signals and errors in measurements. Continue holding the transducers onto the surface of the material until a consistent reading appears on the display, which is the time in microsecond for the ultrasonic pulse to travel the distance ‘L’. The mean value of the display readings should be taken when the units digit hunts between two values.

Pulse velocity=(Path length/Travel time)

v) Separation of transducer leads: It is advisable to prevent the two transducer leads from coming into close contact with each other when the transit time measurements are being taken. If this is not done, the receiver lead might pick-up unwanted signals from the transmitter lead and this would result in an incorrect display of the transit time.

Interpretation of Results
The quality of concrete in terms of uniformity, incidence or absence of internal flaws, cracks and segregation, etc,indicative of the level of workmanship employed, can thus be assessed using the guidelines given below, which have been evolved for characterizing the quality of concrete in structures in terms of the ultrasonic pulse velocity.