PENETRATION TEST


PENETRATION TEST
( IS : 1203 – 1978 )

INTRODUCTION:

Penetration test is the test on bitumen to grade the material in term of its hardness.

Object:

To determine the penetration of bitumen by penetration test.

Apparatus:
a) Container:  A flat-bottomed cylindrical metallic container 55mm in diameter and 35mm or 57mm in height.
b) Needle:  A straight, highly polished hard steel needle.
c) Water bath:  A water bath is maintained at 25 +/- 10C containing not less than 10 liters of water, the sample is immersed to depth not less than 100mm from the top and supported on a perforated shelf not less than 50mm from the bottom of the bath.
d) Penetrometer:  Electrically operated automatic penetrometer / Manually operated penetrometer. It is an apparatus, which allows the needle assembly of gross weight 100gm to penetrate without appreciable friction for the desired duration of time 5 sec. The dial is accurately calibrated to give penetration value in units of one tenth of an mm.
e) Transfer tray:  A small tray, which can keep the container fully immersed in water during the test.
f) Stop Watch.

Procedure:

The bitumen is softened to a pouring consistency between 750C and 1000C above the approximate temperature at which bitumen softens. The sample material is thoroughly stirred to make it homogenous and free from air bubbles and water. The sample material is then poured into the containers to a depth at least 15 mm more than the expected penetration. The sample containers are cooled in atmosphere temperature not lower than 130C for one hour. Then they are placed in temperature controlled water bath at a temperature of 250C for a period of one hour.

The sample container is placed in the transfer tray with water from the water bath and placed under the needle of the penetrometer. The weight of needle, shaft and additional weight are checked. The total weight of this assembly should be 100gm.

Using the adjusting screw, the needle assembly is lowered and the tip of the needle is made to just touch the top surface of the sample, the needle assembly is clamped in this position. The contact of the tip of the needle is checked using the mirror placed on the rear of the needle. The initial reading of the penetrometer dial is either adjusted to zero or the initial reading is taken before releasing the needle. The needle is released exactly for a period of  5 secs. by pressing the knob and the final reading is taken on the dial. At least three measurements are made on this sample by testing at distance of not less than 10mm apart. After each test the needle is disengaged and cleaned with benzene and carefully dried. The sample container is also transferred in the water bath before next testing is done so as to maintain a constant temperature of 250C. The test is repeated with sample in the other containers.

Results:

The difference between the initial and final penetration readings is taken as the penetration value.

Bitumen Grade      A35 &S35   A45 & S45   A55 & S55   A65 &S65   A90 &S90   A200 & S200
Penetration Value        30 to 40     40 to 50     50 to 60       60 to 70     80 to 100     175 to 225







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