When it comes to bitumen, one of the most important ways to classify it, is by its penetration grade. But what does that actually mean?
Simply put, penetration grade measures how hard or soft the bitumen is. To figure this out, experts perform a simple test: they press a standard needle into a bitumen sample under controlled conditions—specific weight, temperature, and time—and then see how deep it goes. The result is measured in something called “pen units,” which are just tenths of a millimeter.
So, if you hear about bitumen with a 60/70 penetration grade, it means the needle sank between 6 and 7 millimeters into the bitumen. The lower the number, the harder the material; the higher the number, the softer it is.
Penetration grade bitumen is especially popular in road construction, where different projects might need different levels of hardness to handle weather, traffic, and wear over time. It’s also commonly used in making waterproofing materials.

Penetration grade bitumen comes in a few different types, each designed for specific weather conditions and traffic loads. The grades are usually shown as two numbers, like 60/70 or 80/100, which tell you how soft or hard the bitumen is.

Here are some of the common types you might come across:

– 30/40: This one’s very hard and tough—perfect for hot climates where softer bitumen would melt or deform.
– 40/50: Still quite hard, great for heavy-duty roads that get a lot of traffic, especially in warm areas.
– 50/70: A bit more flexible, often chosen for places with moderate temperatures.
– 60/70: Probably the most popular choice for regular road paving. It strikes a good balance between hardness and flexibility.
– 80/100: Softer and better for colder regions where the bitumen needs to stay flexible even in low temperatures.
– 100/120: The softest of the bunch, usually used in very cold climates or for lighter-use roads.

Basically, the harder the bitumen, the better it handles heat and heavy traffic. The softer grades are chosen when flexibility is more important, like in cold weather.