This article attempts to have a re-look at a comparitive study of bitumen standards acorss Asia and the key differences in evaluation to suit the local needs.
Most of the bitumen producing nations including Saudi Arabia, Thailand, Singapore, Iran, Malaysia and Newzeland in Asia uses the penetration test (ASTM D-5) ( as specified by TNZ/M/1 in Newzeland's standards) as against their Australian counterparts who uses the viscosity of the bitumen to define the grades of bitumen. This has given rise to difference in manufacturing standards between the rest of it's neighbors.
Grades as per D-5, carried out under laboratory conditions at 25 deg C to determine the depth that a weighted needle skins into bitumen specimen over 5 seconds. Thus the higher the grade, the softer the bitumen. It is measured in tenths of a millimeter. 60/70 grade has a depth of penetration between 6 & 7 millimeters.
This test, although look crude, is still internationally used as it serves as a reference point to compare the property of the bitumen at higher temperatures and it’s consistency with regards to Softening point and viscosity.
with reference to it’s physical characteristics, simply at the ambient temperature, are graded as
180/200 Softer Sealing
130/150 Soft Sealing
80/100 Hard Hot mix Asphalt binder, sealing
60/70 Harder Hot mix Asphalt binder
Most of the nations like Newzeland has one or more than one refinery , which cannot cater to their local demand, the additional requirements for the road construction are being imported.
Australia uses the viscosity of the bitumen to define the grades of bitumen. This is in total contrast with the simple and internationally followed standard of Penetration test per ASTM D-5 .
To comply with AS 2008, the viscosity of the bitumen is tested at 60 deg C to define the four grade of bitumen used for pavement construction.
Grade Viscosity International Character Application
Class 50 40-60 No Equivalent Softer Sealing
Class 170 140-200 80/100 Soft Sealing
Class 320 260-380 60/70 Hard Hot mix Asphalt , sealing
Class 600 500-700 40/50 Harder Hot mix Asphalt
Viscosity is basically a measure of consistency and higher the viscosity , the harder the bitumen gets.
The advantages of using Viscosity over the Penetration tests are
• Viscosity is independent of the test system and the sample size.
• At 60 deg C, the testing range is close the pavement temperature
• Comparative studies of viscosity over a range from 60-150 deg C yields the bitumen’s temperature susceptibility.