Proper Asphalt Paving Methods

Sub-base

• An asphalt driveway is as sturdy as its sub-base, the soil support beneath the layers. Generally, clay is considered a weak soil for an asphalt driveway because it tends to deform under heavy loads. Poorly draining soil causes asphalt driveways to become weak, leading to failure. Install drain tile beneath the asphalt base to prevent the soil from softening. You can then install layer of protective fabric above the sub-base to prevent the soil mixing with the gravel base, preventing further structural weaknesses. Also, compact the soil before applying the 6-inch-minimum gravel base. If you are unsure about your driveway's soil and subsequent permeable quality, consult with the local agricultural office to examine maps detailing the types of soil in your area.

Base

• Remove the existing driveway if necessary. The underlying soil should still be compacted and properly graded for drainage. A 1/4-inch slope per foot is required to prevent water build-up on the new driveway. Two types of bases are recommended for an asphalt driveway; a 6-inch layer of gravel or an asphalt base. Gravel allows for sufficient permeability and is ideal for areas without clay-like soil. An asphalt base is a larger aggregate mixed into asphalt and does not have to be as thick as a gravel base. An asphalt base is premium for clay-like soil or if you anticipate heavy loads on the driveway.

Repaving

• Many different types of mixes of asphalt paving materials are available. The type, size and quality of asphalt cement and the aggregate account for the differences. For a very smooth and finished driveway, the required mixture should have smaller aggregate. The first layer will be slightly thick (2 inches) and have larger rocks. The finish layer will be thin (1 inch) and have smaller stones and coarse sand. Apply a tack coat of asphalt between the layers for bonding. If repaving, you need to remove all dust, dirt and vegetation from the old surface. If you didn't remove the existing driveway, fill any low spots or cracks with patching material prior to applying the finish layer of blacktop.

Maintanence

• Reseal the driveway after one year with a high-quality commercial sealer that is a bituminous water emulsion. If the driveway was sloped, use a sealer containing sand. Sealers are similar to coats of paint and you should not apply them too often or thick. Otherwise, the driveway will crack and peel. Asphalt driveways require sealing when they show obvious signs of wear or when the surface color lightens.