Price and purchase of Bitumen for Road
The ductility of bitumen is its suitability for elongating under traffic loads without cracking in road construction applications.
bitumen for road construction
The elasticity test on bitumen is used to measure the distance in centimeters it stretches before it breaks. This article discusses the required equipment, principles, methods, precautions, inspections, reports, and recommended softness values for bitumen.
Ductility Test on Bitumen
Bitumen hardness test is used to measure the following:
The elasticity of a given bitumen sample is measured
The suitability of bitumen for use in road construction is measured.
The elasticity of bitumen is the distance through which it expands in centimeters before breaking when placed in a standard briquette under standard conditions.
A standard temperature of 25oC should be maintained. A mold having a cross section of 100 mm X 100 mm is prepared at a certain temperature, the excess bitumen is removed and the chips are hooked after zeroing the needle.
The sample is stretched at a rate of 50 mm per minute until fracture. The breaking point distance in cm is a ductility value that depends on temperature, briquette dimensions and strain rate. Efficiency values can vary from 5 to 100 cm.
A minimum value of 5 cm is required for bitumen grade 45 and above. Of interest to you: Moisture Test Course (DPC) - Application Methods of DPC in Construction. Bitumen flexibility test equipment.
Essentially the following equipment is required:
Standard size briquettes.
Traction device with distance measurement dial.
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Arrangement of water bath.
Bitumen elasticity test procedure.
The bitumen sample is heated to a liquid state and poured into a briquette array and placed on a brass plate.
The entire apparatus including bitumen briquettes with brass plate is allowed to cool in air.
A hot knife is used to cut the excess bitumen and also the surface is leveled with the help of a hot knife.
The whole assembly now is kept in a bath maintained at 27 oC for about 85 to 95 minutes.
The side of the mold removed, the clips hooked on the machine, and the pointer adjusted to zero value or initial reading noted.
Now the clips are pulled apart horizontally at the rate of 50 mm per minute and the distance up to the point of the breaking of a thread is noted. This distance in cms gives the value of the ductility of bitumen.
The ductility of bitumen may vary from 5 to over 100 for different bitumen grades, but for satisfactory performance, it should not be less than 50.
The ductility of bitumen is dependent upon pouring temperature, dimensions of the briquette, test temperature, the rate of pulling, etc.
Ductility of Bitumen Suitability for Road Construction
For the purpose of flexible pavement design, it is necessary that binders should form a thin ductile film around aggregates so that the physical interlocking of the aggregates is improved.
bitumen for road paving
Apparatus Required for Ductility Test on Bitumen:
The apparatus as per IS: 1208-1978 consists of: (i) Briquette mold: It is made of brass. Circular holes are provided at ends called clips to grip the fixed and movable ends of the testing machine. The mold when properly assembled form a briquette specimen of following dimensions:
Total length 75.0 ± 0.5 mm
Distance between clips 30.0 ± 0.3mm
Width at mount of slip 20.0 ± 0.2mm
Width at minimum cross-section (half way between clips) 10.0 ± 0.1mm
Thickness throughout 10.0 ± 0.1mm
(ii) Water bath: A bath maintained within 27.0° ±0.1 °C of the specified test temperature containing not less than 10 liters of water, the specimen being submerged to a depth of not less than 10 cms and supported on a perforated shell and less than 5 cms from the bottom of the bath.
(iii) Testing machine: For pulling the briquette of bituminous material apart, any apparatus may be used which is so constructed that the specimen will be continuously submerged in water while the two clips are being pulled apart horizontally at a uniform speed of 50 ± 2.5 mm per minute. (iv) Thermometer: Range 0-44°C and readable up to 0.2°C.
Theory of Ductility Test on Bitumen
The ductility test gives a measure of adhesive property of bitumen and its ability to stretch. In flexible pavement design, it is necessary that binder should form a thin ductile film around aggregates so that physical interlocking of the aggregates is improved.
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Binder material having insufficient ductility gets cracked when subjected to repeat traffic loads and it provides pervious pavement surface.
Ductility of a bituminous material is measured by the distance in centimeters to which it will elongate before breaking when two ends of standard briquette specimen of material are pulled apart at a specified speed and specified temperature.
Procedure of Ductility Test on Bitumen
Melt the bituminous test material completely at a temperature of 75°C to 100° C above the approximate softening point until it becomes thoroughly fluid.
Strain the fluid through IS sieve 30.
After stirring the fluid, pour it in the mold assembly and place it on a brass plate. In order to prevent the material under test from sticking, coat the surface of the plate and interior surfaces of the sides of the mold with mercury or by a mixture of equal parts of glycerin and dextrin.
After about 30-40 minutes, keep the plate assembly along with the sample in a water bath. Maintain the temperature of the water bath at 27° C for half an hour.
Replace the mold assembly in water bath for 80 to 90 minutes.
Remove the sides of the mold.
Hook the clips carefully on the machine without causing any initial strain.
Adjust the pointer to read zero.
Start the machine and pull clips horizontally at a speed of 50 mm per minute.
Mean of two observations rounded to nearest whole number is ductility value. Note: Machine may have a provision to fix two or more molds so as to test three specimens simultaneously.
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