Rigid pavement is the technical term for any road surface made of concrete. Concrete roads are called rigid while asphalt-covered roads are flexible. These terms refer to the amount of deformation created in the road surface itself when in use and over time. The largest advantages to using concrete pavement are in its durability and ability to hold a shape. There are three basic types of rigid pavement commonly used worldwide.
The basic design of rigid pavement is very simple. A surface layer, made up of slabs of Portland cement concrete (PCC), sits on top of a handful of sub-layers. The layer directly under the PCC is more flexible than the concrete, but still quite rigid. This layer provides a stable base for the PCC as well as assists in drainage. Some roads have a second sublayer under the first that is even more flexible, while some simply have the existing soil. The biggest factor in deciding whether this second layer is necessary is the composition of the existing material.
Flexible and rigid pavement are the two basic styles of road surfaces. Flexible pavement is almost always asphalt while rigid pavement is concrete. The difference between these two styles mostly comes down to deformation. Flexible pavement allows for significant deformation under heavy loads; this means the road will bend when placed under stress. Rigid pavement will remain fixed when placed under stress and will crack when the stress exceeds its tolerances.
The way concrete pavement deals with cracking is the main difference between the three styles of pavement. The most common style, joined plain concrete (JPC), is made up of slabs with no steel reinforcement. When cracks develop, they should occur in the cracks between slabs, making the road surface easy to repair.
Joined reinforced concrete contains a steel mesh that reinforces the structure of the concrete slab. The concrete slabs used in this style are often much larger than those used in JPC designs. The reinforcement prevents some cracks, allowing the larger slabs to be effective. The cracks, when they appear, still typically occur between slabs.
The third style, continuously reinforced concrete, contains a high quantity of steel reinforcement. These slabs are not designed to crack at connection points—the slab itself cracks. The steel reinforcement holds cracks together so closely that they do not cause structural problems within the slab.
There are two main reasons to use rigid pavement, both of which stem from its hardness. Since the surface is harder, it is also more durable over time. This keeps the road in good working order far longer than softer surfaces. The other advantage of concrete roads is in their shaping. Since the surface can withstand a lot of weight without deformation, it is possible to create groves and channels in the road to provide extra traction and move water off the road’s surface.