Stripping: Moisture Damage Inside the Asphalt

Quick Verdict

Stripping is moisture damage that happens inside the asphalt, where water breaks the bond between the binder and the aggregate. When that bond fails, the binder peels off the stones and the mix loses its strength from within — the asphalt literally comes apart layer by layer, which is why it is sometimes called delamination. Because it works from the inside, you often do not see stripping until it surfaces as raveling, potholes, or a layer separating. It is especially a problem in wet climates like Oregon's, where water is constantly available to get into the mix. The defenses are keeping water out with good drainage and using anti-strip additives in the mix.

What Stripping Is

In a healthy asphalt mix, the binder coats every piece of aggregate and grips it tightly, and that grip is what gives asphalt its strength. Stripping is the failure of that grip. Water that gets into the mix gets between the binder and the stone and breaks the adhesion, so the binder strips away from the aggregate. The mix goes from a strong, bound material to loose, uncoated stones held together by failing binder.

Because it starts inside, stripping is one of the harder distresses to diagnose from the surface. It is mapped among the moisture-driven structural distresses on our pavement distress diagnosis guide, and it is closely related to the surface effects of water damage in asphalt.

Why Stripping Happens

Stripping needs water inside the mix and a binder-aggregate bond vulnerable to it.

• Water in the mix. Water reaches the interior of the pavement through surface cracks, open joints, a porous poorly compacted surface, or up from a wet base. Once inside, it goes to work on the bond.
• Incompatible aggregate. Some aggregates do not bond well with binder, especially in the presence of water. These are more prone to stripping unless treated.
• No anti-strip additive. Additives (including hydrated lime) improve the binder-aggregate bond and its resistance to water. A mix made without them in a wet climate is more vulnerable.
• Poor drainage. Anything that keeps the pavement wet — a saturated base, standing water, poor grading — feeds stripping by keeping water in contact with the mix.

Why Wet Oregon Is Prime Stripping Territory

Stripping is fundamentally a water problem, and Oregon has water for most of the year. The long wet season keeps surfaces and bases damp for months, so water is almost always available to work into the mix. Coastal pavement deals with constant dampness. Surfaces with standing water in birdbaths, or sitting over a poorly drained, saturated base, stay wet from below. All of this gives stripping the moisture it needs. That is why mix design and drainage matter so much here — a mix specified with anti-strip additives and a pavement built to drain resists stripping far better in our climate.

How Stripping Shows Up

Since you rarely see stripping directly, you read it through its symptoms.

Symptom	What It Suggests
Surface raveling for no obvious aging reason	Binder losing grip from moisture
Potholes forming where water collects	Mix failing internally, then punching out
A surface layer separating or delaminating	Bond failure between or within lifts
Soft, crumbling asphalt when cored or dug	Stripping inside the mix

Because stripping undermines the mix from within, it feeds raveling asphalt on the surface and contributes to how potholes form where water sits.

How to Fix and Prevent Stripping

Stripping cannot be sealed away, because the damage is inside the mix.

1. Remove the stripped material. The affected asphalt has lost its strength and has to be milled or dug out. There is no surface treatment that re-bonds binder to aggregate inside a failed mix.
2. Fix the water source. Repair drainage, eliminate standing water, and dry out the base so the new asphalt is not immediately exposed to the same moisture.
3. Use a stripping-resistant mix. Replace with a mix made with compatible aggregate and anti-strip additives suited to Oregon's wet conditions.
4. Keep water out going forward. Seal cracks and maintain drainage so water cannot get back into the mix and restart the process.

What It Costs

Industry Baseline Range: removing stripped asphalt, addressing drainage, and replacing with a stripping-resistant mix runs in the range of $6 to $15 per square foot+, depending on depth and the extent of base and drainage work. These are industry baseline ranges for planning only — actual pricing depends on lot size, access, condition, and current market conditions. Get a site-specific quote.

Current Market Reality

Stripping is mostly prevented at the mix-design and drainage stage, which is far cheaper than repairing it after the fact. In wet Oregon, paying for a mix with anti-strip additives and a pavement built to drain is cheap insurance against a problem that destroys asphalt from the inside. Once stripping has set in, there is no shortcut — the failed material has to come out, so catching the water source early limits how much.

The Bottom Line

Stripping is water breaking the binder-aggregate bond inside your asphalt, destroying the mix from within and surfacing as raveling, potholes, and delamination. Wet Oregon is prime territory, so the defenses are keeping water out with drainage and using anti-strip additives in the mix. Once it sets in, the failed material has to be removed. Cojo provides asphalt repair services across Oregon and specs mixes for our wet conditions. Request an assessment and we will check what is happening below your surface.