Concrete Paving

Concrete pavements (specifically, Portland cement concrete) are created using a concrete mix of Portland cement, gravel, and sand. The material is applied in freshly-mixed slurry, and worked mechanically to compact the interior and force some of the thinner cement slurry to the surface to produce a smoother, denser surface free from honeycombing. Cement concrete can be either reinforced or non-reinforced. Non-reinforced pavements will typically have joints at a 5 meter interval. Reinforced concrete pavements can have a much longer joint spacing, or no built-in joints at all. Typical reinforcement used includes “rebar” (reinforcing steel) or wire mesh or both.

Vertical misalignment of the joints, known as joint faulting, can be caused by differential settlement of the substrate, and are a source of driver annoyance. A common failure mode of concrete pavements is loss of support of the slab edges or corners due to erosion of the foundation material. If this condition is caught before it leads to breakup of the slab, support can be restored by filling the void with grout or foam in a process known as “mud jacking” or “slab jacking”.

Advantages of cement concrete roadways include that they are typically stronger and last longer than asphalt concrete pavements. They also can easily be grooved to provide a durable skid-resistant surface. Disadvantages are that they have a higher initial cost, are more difficult to repair, and are also somewhat noisy if jointed, but unjointed concrete pavement is actually a method of road noise mitigation.

The record for first mile of concrete pavement to be laid in the United States is claimed by Michigan.

Bituminous Surface Treatment (BST)

Bituminous Surface Treatment (BST) is used mainly on low-traffic roads, but also as a sealing coat to rejuvenate an asphalt concrete pavement. It generally consists of aggregate spread over sprayed-on asphalt emulsion or cut-back asphalt cement. The aggregate is then embedded into the asphalt by rolling it, typically with a rubber-tired roller. BSTs of this type are described by a wide variety of regional terms including “chip seal”, “tar and chip” and “seal coat”.

Other types of BSTs include micropaving, slurry seals and Novachip. These are laid down using specialized and proprietary equipment. They are most often used in urban areas where the roughness and loose stone associated with chip seals is considered undesirable.