What Are Aggregate Surface Pop-Outs?
If you’ve noticed small voids or missing stones in your asphalt surface, you may be seeing what’s known as aggregate surface pop-outs. While they can look concerning at first glance, they’re a common and generally cosmetic occurrence in asphalt pavement — especially in northern climates like ours.
Let’s break it down.
What Are Aggregates?
Aggregates are the small, granular materials — such as crushed stone, gravel, sand, and slag — that are blended with asphalt cement (bitumen) to create asphalt pavement. These materials provide strength and structure to the finished surface.
When one of those aggregate particles becomes dislodged from the surface, it leaves behind a small cavity. This is called a pop-out. Pop-outs can vary in size, depending on the size of the stone used in the mix.
Why Do Pop-Outs Occur?
There are several reasons aggregate pop-outs can happen:
- Use of softer aggregates
- Moisture damage
- Snowplow impact
- Heavy traffic
- Repeated freeze-thaw cycles
- Severe winter conditions
In regions like Minnesota, freeze-thaw cycles are a major contributor. As moisture enters the pavement and temperatures fluctuate, expansion and contraction can loosen some surface stones.
Pavements that contain softer or lower-quality aggregates may experience pop-outs more quickly than those made with harder stone. However, many areas of the state have successfully used locally sourced aggregates — including softer materials — for over 50 years.
Typically, pop-outs occur gradually over the first several years after installation. In particularly harsh winters with frequent plowing and temperature swings, a majority of pop-outs may appear during the first winter.
Do Surface Pop-Outs Affect Pavement Life?
The short answer: No.
Based on pavement history and performance data, surface pop-outs do not impact the long-term structural integrity of asphalt pavement.
Modern asphalt mix designs ensure that asphalt cement thoroughly coats the aggregate, helping protect against freeze-thaw damage. While pop-outs affect the surface appearance, they do not indicate structural failure.
Will Water in Pop-Outs Cause More Damage?
This is one of the most common concerns we hear.
Because pop-outs create small, unconfined surface voids, water that enters these impressions does not typically cause additional freeze-thaw damage. Asphalt pavement is designed with air voids that allow water to expand, contract, evaporate, and escape.
In other words, these surface imperfections are not a gateway to deeper structural issues. If you’re noticing large breakage alongside pop-outs, repairing cracked asphalt warrants attention.
The Sustainability of Local Aggregates
Using local aggregates — sourced from nearby quarries — significantly reduces transportation distance, fuel use, and overall energy consumption.
While some regions have limited high-quality aggregate resources, softer local aggregates have performed successfully for decades. Utilizing these materials supports sustainability efforts while maintaining reliable pavement performance.
What Can Be Done About Pop-Outs?
In most cases, surface pop-outs are considered an aesthetic issue rather than a structural problem. They do not require immediate repair.
If appearance is a concern, seal coating may improve surface uniformity. Contact our residential asphalt paving team to discuss whether seal coating is right for your pavement.
Final Thoughts
Northern climates present unique challenges. Seasonal fluctuations, snowplowing, and freeze-thaw cycles all impact pavement surfaces over time.
Despite these challenges, asphalt has a long and proven track record of delivering smooth, durable, and economical roadways throughout Minnesota and Wisconsin.
