7.3.7. Stripping Value Test

• Purpose: Evaluates adhesive property between bitumen and aggregates.

The main goal of the Stripping Value Test is to assess how well bitumen adheres to aggregate materials. This is important in pavement construction because strong adhesion ensures that the surface remains intact and durable under various conditions, especially when exposed to moisture. If the bond between the bitumen and the aggregates is weak, it can lead to stripping, where the bitumen separates from the aggregates, reducing the quality and lifespan of the pavement.

Think of the bitumen like glue and the aggregates like pieces of a puzzle. For the puzzle to hold together perfectly, the glue must stick well to all pieces. If there are areas where the glue doesn't hold, those pieces will fall off over time, just like how bitumen can wash away from aggregates if the adhesion isn't strong enough.

• Apparatus: Beaker, hot plate.

The apparatus needed for the Stripping Value Test includes a beaker and a hot plate. The beaker is used to boil water, and the hot plate provides a controlled heat source for boiling. These items are essential because the test involves boiling bitumen-coated aggregate samples in water to observe how much bitumen separates from the aggregates during this process.

Imagine you're boiling pasta in a pot. Just as you watch the pasta soften and release starch into the water, in this test, we observe how the heat from boiling water affects the bond between bitumen and aggregate.

• Procedure: a. Bitumen-coated aggregate samples are boiled in water. b. Visual inspection for stripping of bitumen film.

The procedure for the Stripping Value Test involves two main steps: first, the bitumen-coated aggregates are boiled in water. Then, after boiling, the test requires a careful visual inspection to determine whether any bitumen has separated from the aggregates. This visual inspection helps quantify how well the bitumen adheres to the aggregates after exposure to heated water.

Consider how you might check if your toast is buttered evenly. After applying the butter, you could hold the toast up to the light to see if there's any dry spot. Similarly, in this test, we visually inspect the aggregates to identify any places where the bitumen has come off.

• Result: <25% stripping is acceptable.

The results of the test tell us how much bitumen has separated from the aggregates during boiling. A target is set at less than 25% stripping, which means that if more than 25% of the bitumen has come off during the test, the quality of the material is deemed unsuitable for use in pavement construction due to inadequate adhesion.

Imagine a situation where you apply waterproof paint to a surface. If over 25% of the paint starts peeling off after a rainstorm, you’d consider that outcome unacceptable. Likewise, in road construction, if too much bitumen strips from the aggregates, it indicates a potential failure point in the road's surface.

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