Recycled Concrete as a Base Under Asphalt

Clean recycled concrete aggregate can work as a driveway base when the gradation is right and it is compacted in lifts. It is not a dump of sidewalk chunks, and it is not asphalt millings.

Open free asphalt tonnage calculator →

What you want from the pile

Recycled concrete aggregate, often called RCA, is crushed concrete processed to a gradation. Under asphalt it has one job: lock into a stable base that drains as the product is intended to drain and does not heave with trash in it. Ask the quarry what size they are selling, whether fines are included, and whether the pile is clean of wood, plastic, and reinforcing mesh. Large slab fragments with wire in them are demolition, not base. Millings are recycled asphalt and behave differently because they still contain binder. Do not swap the names on the order and hope the truck sorts it out. The day's price is the quarry's quote. A planning weight of about 1.4 tons per cubic yard is only a start for compacted crushed products. Confirm RCA specifically, because it may not match the stone factor you used last time.

How it interacts with water and asphalt

Some recycled concrete products can be moisture sensitive or can stiffen as leftover cement reacts. That can be helpful when it is compacted correctly and a problem when it is placed as a wet, segregated dump. Fines that pump to the surface will reflect into the asphalt as cracks. A very open, chunky layer can shift under steering loads if it never had fines to lock. You want the product the quarry recommends for a driveway base, placed in lifts. Do not cap a loose RCA pile with a thin asphalt skin so it 'looks finished.' Thickness of asphalt is a separate design. Estimate those tons with length, width, and asphalt thickness at AsphaltTons.com, using about 145 pounds per cubic foot as a planning default in the 140 to 150 range, and confirm with the plant. A measuring wheel sizes the area and is not a survey.

A practical acceptance check

Look at a delivery before it is all on the ground. Pick out wood, clumps of soil, and long steel if they appear, and reject a load that is mostly debris. Compact a test strip. If it ruts and will not tighten, stop and call the quarry rather than covering it. Keep RCA away from a drainage path you need to stay open if the fines could wash. At the edges, confine the material so it does not unravel into the lawn. After paving, a crack that follows a poorly compacted RCA edge is a base crack. Sealcoat will not stitch it. If you are comparing RCA with crushed stone, ask both suppliers for the product they would place under a passenger-car driveway and how thick they want it. Write that next to the asphalt thickness so the two layers are not blended into one vague 'blacktop' number.

A practical sequence

Order a graded recycled concrete base product, not broken slab chunks.
Confirm the tons-per-yard factor and the price with the quarry that day.
Compact in lifts and reject loads full of wood, soil, or mesh.
Order asphalt tons separately for the pavement thickness you specified.

The mistake to skip

Spreading broken concrete rubble with steel in it and calling it a compacted base.

Questions people ask

Is recycled concrete the same as asphalt millings?

No. Concrete aggregate has no asphalt binder. Millings do. They compact and drain differently.

Can I put asphalt directly on old concrete pieces?

Only if they are a sound, stable slab you have chosen to overlay, not a loose pile of chunks. Loose rubble has to be processed and compacted or removed.

As an Amazon Associate, AsphaltTons.com earns from qualifying purchases. Product links below are sponsored.