What is Asphalt Stripping? What Causes Asphalt Stripping?
What is Asphalt Stripping?
Asphalt stripping is essentially the opposite of asphalt raveling. Rather than the top layer disintegrating and exposing the lower layers, it is the lower layers that fall apart first, weakening and damaging the upper ones.
More specifically, aggregate materials and asphalt binder at the bottom of the asphalt layer start to come apart, causing the pavement to lose structural support and crumble from beneath.
This can cause a whole host of problems on the surface such as rutting, shoving, raveling, and severe cracking.
What Causes Asphalt Stripping?
Moisture at the base of the asphalt layer can lead to certain aggregates disconnecting from the oil-based adhesives that keep the asphalt intact.
Although an inadequate asphalt mix may be a contributing factor, water access or inadequate drainage will likely be the primary cause of this issue.
How Do You Solve Asphalt Stripping Problem?
It can be difficult to pinpoint stripping as the main issue since it occurs beneath the surface. The visible signs of asphalt deterioration could have many possible sources, so a professional should be consulted.
Taking a core sample from the pavement can provide a better view of what is happening and if stripping is uncovered, it must be addressed by making changes that prevent moisture penetration in the future.
What Is Stripping Test In Road?
The static immersion method is used to determine the stripping value of aggregates for bitumen and tar binders. This is calculated as the ratio of uncovered area to total aggregate area, expressed as a percentage.
For this method to be successful, the aggregate must be dry and not overly dusty so that the bitumen or tar can adhere properly.
Stripping may be an issue with water-permeable bituminous mixtures. This test outlines the procedure for determining stripping value using the static immersion method.
What Is Stripping Of Aggregate?
The adhesion between asphalt binder and aggregates typically begins to weaken from the bottom up of the HMA layer.
When water causes displacement of asphalt from the surface of aggregate particles, leading to deterioration down its surface, it is known as raveling.
While the specifics of this process are still not completely understood, research has identified that differences in mineralogy and chemical composition of an aggregate can play a role (Roberts et al., 1996[1]).
Generally speaking, aggregates which have an affinity for water (hydrophilic) are usually acidic and more prone to stripping following exposure to moisture.
Oppositely, those that prefer asphalt over water (hydrophobic), being typically basic in nature, do not suffer as severely from stripping events.
Moreover, the surface charge that aggregates exhibit when interacting with liquid may result in varying levels of adherence to asphalt cement and subsequent susceptibility to water damage.