What is the difference between IS 702 bitumen and IS 73 bitumen?

IS 702 covers industrial or 'blown' bitumen used mainly for waterproofing and roofing, whereas IS 73 covers straight-run viscosity-graded paving bitumen used for road construction.

What does a grade of '85/25' mean?

It indicates the physical properties of the bitumen: an approximate softening point of 85 °C (range 80-90) and a penetration value of 25 (range 20-30 at 25°C).

How is the softening point of industrial bitumen tested?

It is tested using the Ring and Ball method as specified in IS 1205.

Is ductility an important parameter for industrial bitumen?

Yes, but required values are much lower than paving bitumen. For example, Grade 85/25 requires a minimum ductility of 3 cm at 25°C (Table 1).

IS 702

: 2017

Industrial Bitumen - Specification

CurrentFrequently UsedSpecificationMaterials Science · Waterproofing and Damp Proofing

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This code covers the requirements and testing methods for industrial bitumen, heavily used in waterproofing, damp-proofing, roofing felt manufacture, and mastic asphalt. It categorizes industrial (oxidized/blown) bitumen into different grades based on their softening point and penetration properties.

Specifies requirements for various grades of industrial bitumen used in different applications, including waterproofing.

Quick Reference Values

solubility in trichloroethyleneMinimum 99.0%

loss on heating max0.2% by mass (for most grades)

flash point cleveland open cupMinimum 225 °C (for most grades)

grade 85 25 softening point80 °C to 90 °C

grade 85 25 penetration20 to 30 at 25°C

grade 90 15 softening point85 °C to 95 °C

Practical Notes

Industrial bitumen is manufactured by blowing air through hot asphaltic flux (oxidized bitumen), making it rubbery and less temperature-susceptible compared to paving grades.

Grades are denoted by two numbers (e.g., 85/25); the first represents the target softening point (°C) and the second represents the target penetration at 25°C.

Strict temperature control is critical when heating bitumen on site. Heating above the recommended application temperature or flash point degrades the material's waterproofing properties and poses a severe fire hazard.