Bases and subbases play an important role in giving concrete pavement a firm foundation.
Building a road, walkway, driveway or other concrete pavement structure requires a number of steps. One important step is the creation of subbases and bases for the concrete pavement to rest upon. These base layers provide a sound foundation and lend strength and support to the concrete pavement’s top layer. However, subbases and bases are not one-size-fits-all; there are many different options for the base layers under concrete pavement.
Concrete Pavement Base and Subbase Options
The most important factor that goes into bases and subbases for concrete pavement is not thickness, but uniformity. The best, most effective bases and subbases for concrete pavement are uniform in the support they provide. Uniform support helps concrete pavement handle the loads traveling on it and to mitigate stress on subgrades.
Bases and subbases today are constructed of asphalt or concrete paving equipment that can provide a smooth surface for the concrete pavement. They should be stiff, but not too stiff to be able to adjust to changes in the concrete pavement slab. Curling, warping, and cracking can all be a result of a base that is too stiff.
Common options for bases and subbases, and the materials used for them, include:
Granular bases (also known as unstabilized bases)
These bases are made of granulated particles, such as rock, sand, and other aggregates or mixtures. They are the most commonly used type of base for concrete pavements.
- Dense-graded aggregate base
- Open-graded aggregate drainage layer
These bases are made of materials that are rigid and stable.
- Cement-stabilized bases, like cement-treated bases, lean concrete bases, and cement-treated open-graded drainage layer.
- Asphalt-stabilized bases, such as an asphalt dense-graded base, asphalt-treated base and asphalt-treated open-graded drainage layer.
Recycled materials are also an option for making bases and subbases, in addition to virgin aggregates. Recycled, crushed concrete is the most commonly used recycled material to make bases and subbases, and it’s a good choice when the project has a focus on sustainability.