Stripping Value Test on Road Aggregates

The bitumen and tar are used as a binding agent. It is mixed with the aggregates in construction of roads.

They are easily blendable when the aggregates are in dry condition. In case of water presence in bitumen mixture, it will affect the bitumen bonding with the aggregates and shall disintegrate the road.

So, many different tests on bitumen have been conducted to find the quality, strength and durability.

What is Stripping Value Test?

The primary purpose of stripping value test is to determine the presence of water molecules in adhesion between the bitumen and aggregates. The stripping value test results are based on visual observation.

Application of stripping value test

The adhesion is good between the aggregates and bitumen when the aggregates are free from wet and dust. If the water is present in the aggregates, then adhesion happens between the aggregates and bitumen or tar will become weak.

So, the stripping value test is conducted to evaluate the bitumen binder, whether it is suitable or not for road construction.

The stripping value of aggregates determined by static immersion method as per IS code 6241.

How to find the stripping value of road aggregate?

The stripping value is calculated in percentage by the ratio of uncovered area aggregates which is not coated by bitumen to the total aggregates area. 

Apparatus Required

• Oven
• Water Bath
• Beaker with 500ml capacity
• Sieve as per IS standard 20mm and 12.5mm
• Batch mixer to mix the bitumen and aggregates

Test procedure

• Take the dried aggregate of 200g and place in the 20mm sieve. Now shake the sieve and collect the retained aggregate from 12.5mm sieve.
• Then take the bitumen binder at 5 % of the aggregate weight.
• Now heat the collected aggregates at 150°C and heat the bitumen binder at 160°C.
• Then the aggregates and bitumen should be mixed well until the bitumen coat completely covers the aggregates.
• Now relocate the mixture into the beaker and allow it cool at room temperature for 2 hours.
• Then add water into the beaker up to the complete sample immersion.
• Now place the beaker on the water bath for 24 hours at 40°C.
• After completion of 24 hours, remove the beaker and allow it to cool at room temperature.

Results

Now the striping area can be calculated visually. Estimate the uncoated area by bitumen.

Stripping Value of Aggregates = (uncovered area aggregates / Total area of aggregates) x 100

The stripping value of aggregates = …. %

At least 3 sample aggregates should be tested, and the average value is the stripping value of the aggregates. The stripping value should not be more than 5% of the total aggregate area. 

Lab Report 

Precaution

• The aggregates should be free from dust and moisture.
• Distilled water should be used in this test.
• Ensure the proper mixture of bitumen and aggregates.

Happy Learning 🙂