ABSTRACT

The foundation beneath a pavement is frequently constructed in either a low strength cracked cement bound material or a higher-quality concrete material. UK practice is to construct heavily trafficked URC, JRC and CRCP pavements across high-quality cement bound materials, the high-quality material providing support to the surface slab system. High-quality cement bound materials can also be used with bituminous materials to form flexible composite pavements. Lower-quality sub-base materials are also used with bituminous pavements but their lack of tensile capacity reduces the structural value of the material. Flexible composite (or semi-rigid) pavements are distinctly different to

surface slab systems in that they obtain their strength from a combination of the structural capacity of the bituminous and cement bound layers. Three different groups of structures can be identified:

• Roller compacted concrete (RCC) systems: RCC is principally used in the US and is a strong cement bound material (typically 40 MPa compressive strength) generally used as a complete pavement structure. The material is batched then laid semi-dry using a paver. Cracks are frequently induced as part of the construction process (see Chapter 9). In low-speed applications (ports, industrial areas, estate roads), RCC can actually form the surface; otherwise, a bituminous surface course would be added.