How It's Made: New Construction

New paving on a new site is built in layers. The ground is graded to the right elevations, a base of crushed stone is placed and compacted, a binder course is laid, and a surface course finishes the job. Each layer has a specific role, and the layers only perform as intended when the one beneath them is sound. For parking areas, see parking lot paving.

What happens before paving starts?

Before any asphalt or concrete goes down, the site is cleared and the grades are set. Topsoil and any unsuitable material are removed, and utilities are located and protected. The native soil, called the subgrade, is then proof-rolled, which means driving a loaded truck or heavy roller over it so soft or weak spots show up. Those spots are dug out and replaced or stabilized before the base is placed.

What is the base, and why does it matter?

The base is a layer of crushed stone in graded sizes, so the particles lock together when compacted. It carries the load from above and spreads it over the subgrade. The base is placed in lifts, which are thinner layers, and each lift is compacted before the next is added. Compaction packs the particles tightly so the base will not settle under traffic or freeze-thaw movement.

What is a binder course?

The binder course is the first asphalt layer. It is a hot mix with larger stone particles, and it gives the pavement its structure. It also smooths out small irregularities in the base. A paving machine called a paver spreads the mix to a consistent depth, and rollers compact it while it is still warm.

What is the surface course?

The surface course is the top layer that drivers and pedestrians touch. It is a finer mix designed to resist wear and to provide traction. It also sets the final slope that moves water toward drains, and it is matched to the binder course at joints and edges. Transitions to curbs, gutters, and existing pavement are finished at this stage.

How does drainage fit into new construction?

Pavement has to shed water to last. Grades are set so the surface slopes toward catch basins (storm drain structures that collect runoff) or another approved outlet. If the site is built with the right slope from the start, water runs off instead of standing and soaking into the base. Correcting drainage after paving is far more difficult than building it in at the beginning.

Why does weather matter during construction?

In central Ohio, the timing of each layer depends on the weather. Asphalt must be placed in suitable temperatures and dry conditions, and a frozen or saturated subgrade should not be paved on. Freeze-thaw cycles can damage a base that was placed in wet or frozen conditions, so the schedule has to allow for it.

Frequently asked questions

How soon can new pavement be used?

Traffic is kept off new asphalt until it has cooled and set enough to carry weight. The contractor will advise when it is safe to use.

Who decides the layer thicknesses?

The design of the pavement is based on the expected traffic and the soil conditions. The written estimate should state the thickness of each layer so you can compare bids and confirm what is being built.

Can new paving go down on any ground?

Not without preparation. Soft or wet soils need to be corrected before the base is placed, and that work should be included in the scope.

Bruck Construction serves Columbus and central Ohio and provides free estimates for new asphalt and concrete work. Request a free estimate to talk through your site.