Asphalt millings show up on a lot of job sites — road milling projects, parking lot removals, driveway demolitions. Contractors regularly ask whether a rock separator or grizzly screen can handle millings the same way it handles native rock and soil. The short answer is: it depends on the conditions. Here's what you need to understand before you try it.
What Are Asphalt Millings?
Asphalt millings — also called recycled asphalt pavement (RAP) — are the material produced when old asphalt surfaces are ground up or planed off during road resurfacing work. The resulting material is a mix of angular aggregate and asphalt binder that ranges in size from fine dust to chunks several inches across.
Millings are commonly reused as driveway base, unpaved road surfacing, and parking area fill. They compact well, drain reasonably well, and cost significantly less than new gravel — which is why contractors and property owners want to process and reuse them whenever possible.
Can a Rock Separator Handle Asphalt Millings?
A rock separator can move and sort asphalt millings, but there are important conditions that affect whether it will work well on your specific job.
Temperature Matters Significantly
Asphalt millings behave very differently depending on temperature. In hot weather, the asphalt binder in the millings softens and becomes sticky. Material can clump together, bridge across the screen bars, and stick to the grizzly's steel frame. In cooler conditions — below 70°F or so — millings break apart more freely and behave more like crushed aggregate, making them much easier to screen.
If you're working on an asphalt milling job in summer heat, plan to screen early in the morning when temperatures are cooler, or accept that throughput will be lower than with native rock and soil.
Chunk Size Affects Performance
Fresh millings from a road paving project are often relatively uniform in size. Older stockpiled millings, or material from manual removal work, can include large chunks and slabs that behave more like irregular rock. Larger chunks may not pass over the grizzly bars effectively and will need to be broken down before screening.
Moisture and Curing State
Freshly milled material that hasn't had time to cure behaves differently than millings that have been stockpiled for weeks. Fresh millings are more plastic and sticky. Cured millings are more friable and screen more easily.
Best Practices for Screening Asphalt Millings with a Rock Separator
- Work in cooler conditions — Early morning or fall/spring temperatures improve screening performance significantly
- Use smaller bucket loads — Reduce your load size compared to what you'd use for native rock. Smaller loads allow better separation and reduce the chance of bridging
- Break up large chunks first — Pre-process large slabs before running material over the grizzly
- Clean the grizzly more frequently — Sticky millings can accumulate on bars faster than native rock; plan for more frequent cleaning passes
Choosing the Right D Rock Grizzly Model for This Work
If you're regularly processing asphalt millings, match your model to your skid steer or excavator class and your typical daily volume. The MR10 at 4,500 lbs is a versatile option for mid-size machines handling mixed demolition material. For lighter-duty operations, the LR8 at 1,500 lbs handles smaller volumes efficiently.
D Rock Grizzly equipment is built with heavy steel construction specifically for demanding material conditions. If you have questions about whether a specific model is right for your millings project, contact their team in Crandon, Wisconsin directly.
Frequently Asked Questions
Can a rock separator screen hot asphalt millings?
Hot millings are sticky and tend to clump and bridge across screen bars. Screening is possible but more difficult. For best results, wait until material cools or work during cooler parts of the day.
Will asphalt millings damage my rock separator?
Millings themselves won't damage a properly built rock separator, but the sticky binder can accumulate on bars and frame components. Plan for more frequent cleaning than you'd do with native rock and soil.
What's the best alternative to screening millings with a grizzly?
For very large volumes of hot or fresh millings, a powered trommel or pugmill may be more efficient. For typical contractor-scale jobs, a rock separator grizzly works well in the right conditions.
Can separated asphalt millings be reused immediately?
Yes. Sorted millings can be used directly as driveway base, road surface, or fill material. They compact well when properly applied and are a cost-effective reuse of demolition material.