Asphalt Paving Base Preparation in Casper, Wyoming

A concert at the Casper Events Center can bring up to 9,700 people into one parking area in a single evening, and every car, truck and bus crosses the same few pavement sections. Asphalt is only as good as what is under it. A thin layer of hot mix over a weak base looks fine for one winter and then begins to ravel, rut and pump water through every crack.

Base preparation is the work done after the subgrade is accepted and before the paver arrives. We place the aggregate base in compacted lifts, trim it to the grade that gives the specified asphalt thickness, test it for density and proof-roll it. The surface we hand to the paving crew is the surface the asphalt will copy.

We prepare bases for parking lots, drive lanes, truck courts and private streets. We do not lay the asphalt on most of these jobs, and the paving contractor appreciates it when we provide a clean, tight and dry base. The relationship works best when we talk before the work starts.

Layers between the dirt and the asphalt

A paving section has layers. At the bottom is the subgrade, prepared as described in road subgrade preparation. Above it may be a geotextile, a subbase of coarse aggregate, and a crushed base course of smaller stone. The asphalt goes on top in one or two lifts, with a tack coat between them.

We place the aggregate in layers, spread by grader or paver, wet to the optimum moisture and rolled to the specified density. We trim the final surface with grade control to within a small fraction of an inch. The surface must be tight, with fines filling the voids, and free of loose stone, which will pop out under the paver. Water is applied if the base dries, since a dry surface fails to bond with the tack coat.

Why the base can cost more than the asphalt

Aggregate is heavy and travels by the ton, so base material and haul can make up a large part of a paving budget. A six-inch base over a large lot is thousands of tons of stone. Thickness is the lever, and the engineer sets it from soil strength and traffic load. Increasing it by two inches adds a lot of material.

The price also depends on the subgrade. A good subgrade allows a thinner base, but a poor one forces a thicker section or stabilization. Our proposal separates those quantities so the owner can see them. A commercial developer comparing bids should check that the base thickness and the testing frequency match from one bidder to the next.

Grade control and drainage first

Parking lots fail from water more than from traffic. We set the grade so every square foot of base drains to an inlet, a swale or an edge, without birdbaths. We use a laser or GPS to check the grade at a tight grid, and we fix the low spots in the base, not in the asphalt.

We then roll the base until it is tight. Final rolling is done with a steel drum, and the proof-roll with a loaded truck. If a spot pumps, we dig it out and replace it. We protect the finished base from truck traffic and rain until the paver arrives. When a schedule slips, we re-roll and recheck before the asphalt goes on, since a base that sat for three weeks is not the base we accepted.

Specifications and testing

Many owners specify base density at a high percentage of maximum dry density, with gradation and plasticity limits for the aggregate. Casper commercial permits call for engineered site drawings, and the paving section is shown on those sheets. We submit the aggregate source and gradation before we order, and we hand over the test results for each lift.

The frost line in Casper is three feet and the climate is severe in its weathering, so the base should drain freely and avoid fine, water-holding material. Pavement joints and edges are the other weak points. Base should extend past the pavement edge, and the shoulder must be compacted, so the edge does not break off under wheels.

Lots that serve people and trucks

A retail shopping center has light car traffic across most of the lot and heavy trash and delivery trucks at the back, so we change the section across the site. Campuses like the one at Casper College, which occupies more than 200 acres and 28 buildings, combine parking, service drives and fire lanes in one network.

Industrial sites need heavier sections or concrete. We discuss parking lot concrete as an alternative where trucks are heavy and standing. Some owners choose concrete for dock aprons and asphalt for employee parking, and we prepare the base for both.

Matching the paver's window

Asphalt plants run seasonally, and paving is limited by temperature. A paving crew wants a ready base on a particular day, and a cold snap can shut the plant down. We build float into the schedule so the base is done a week ahead, and we keep an eye on the weather. The Casper Events Center is reached from I-25 exit 189, and lots near busy interchanges also need traffic planning so the base is not torn up by detoured vehicles.

If we cannot finish before the plant closes for the season, we protect the base for winter and finish in spring. That is an owner decision, and we lay out the cost in plain numbers. For sites needing fine trim before paving, fine grading follows the same approach.

Send the paving plan and the section details

We will price base preparation as its own item with a unit cost per square yard, a testing plan and a date when the paving crew can have the surface. Tell us the paving contractor and we will coordinate directly.

Questions Owners Ask

How thick should the aggregate base be under asphalt?

The engineer sets it from the soil and the traffic. Light-duty lots often use four to six inches, and heavier sections use more. We build to the drawings, and we tell you early if the section looks light for the traffic described.

How soon can the paver start after the base is done?

As soon as the base passes the proof-roll and density tests, and the surface is dry. In practice, many crews arrive within a few days. A longer wait requires a check of the base for damage.

Can you prepare a base in cold weather?

Only on unfrozen ground, and the material must not be frozen when placed. Moisture control is harder in cold weather. We schedule base work for the warm months when we can.

What causes a new lot to develop potholes?

Usually water in the base and a weak subgrade. Cracks let water in, trucks pump it out, and the pavement breaks up. A well-drained, well-compacted base prevents the whole cycle.

Do you coordinate with the paving contractor?

Yes. We confirm grade tolerances, the paving date and the access route. We also walk the base with their foreman before the paver arrives, so any concerns are fixed in advance.

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