Sunday, February 6, 2011

DUCTILITY TEST.( IS : 1208 – 1978 )

                                                                        DUCTILITY TEST.
                                                                        ( IS : 1208 – 1978 )



INTRODUCTION:

In the flexible pavement construction where bitumen binders are used, it is of significant importance that the binders form ductile thin films around the aggregates. This serves as a satisfactory binder in improving the physical interlocking of the aggregates.

Object:

To determine the ductility of the bituminous material.

Apparatus:

a) Ductility machine.
b) Briquette moulds.
c) Knife.

Procedure:

The bitumen sample is melted to a temperature of 75 to 1000C above the approximate softening point until it is fluid. It is strained through 90 micron sieve, poured in the mould assembly and placed on a brass plate, after a solution of glycerin and dextrin is applied at all surfaces of the mould exposed to bitumen. After 30 to 40 minutes, the plate assembly along with the sample is placed in water bath maintained at 270C for 30 minutes. The sample and mould assembly are removed from water bath and leveling the surface using hot knife cuts off excess bitumen material. After trimming the specimen, the mould assembly-containing sample is replaced in water bath maintained at 270C for 85 to 95 minutes. The sides of the mould are now removed and the clips are carefully hooked on the machine with out causing any initial strain.

The pointer is set to zero, the machine is started and the two clips are pulled apart horizontally at a uniform speed of 50 +/- 2.5mm per minute. While the test is in operation, it is checked whether the sample is immersed in water at depth of at least 10mm. The distance, at which the bitumen thread of each specimen breaks, is recorded (in cm) to report as ductility value.

Results:
The distance stretched by the moving end of the specimen up to the point of breaking of thread measured in centimeters is recorded as ductility value.
Limits: The minimum ductility value of A35 & S35 grade bitumen is 50 cm at 270C.
              All other grades, the ductility value is 75 cm at 270C.  























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