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Pavement Structure

HMA pavements are flexible pavements. Flexible pavements are so named because the total pavement structure deflects, or flexes, under loading. A flexible pavement structure is typically composed of several layers of material each of which receives the loads from the above layer, spreads them out, then passes them on to the layer below. Thus, the further down in the pavement structure a particular layer is, the less load (in terms of force per area) it must carry (see Figure 1).


Figure 1: Flexible pavement load distribution.

Basic Structural Elements

Material layers are usually arranged within a pavement structure in order of descending load bearing capacity with the highest load bearing capacity material (and most expensive) on the top and the lowest load bearing capacity material (and least expensive) on the bottom. A typical flexible pavement structure (see Figure 2) consists of:


Figure 2: Basic Flexible Pavement Structure

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