Concrete pavements are designed and constructed to provide a durable and comfortable driving surfaces and these are ideal for high traffic highways and airport pavements.
Concrete pavements have been refined into three common types: Continuously Reinforced Concrete Pavement (CRCP), Jointed Reinforced Concrete Pavement (JRCP), and Jointed Plain Concrete Pavement (JPCP).
Continuously Reinforced Concrete Pavement
CRCP is fully reinforced along the entire length. CRCP naturally forms tight transverse cracks to evenly transfer loads. The transverse cracks do not impair the structural integrity of the pavement. Initially, continuously reinforced designs generally cost more than jointed reinforced or jointed plain designs due to increased quantities of steel. However, CRCP can demonstrate superior long-term performance and cost-effectiveness. A number of agencies choose to use CRCP designs in their heavy urban traffic corridors. A couple advantages of concrete pavement is that they are typically stronger and more durable than asphalt roadways. They also can easily be grooved to provide a durable skid-resistant surface.
CRCP was introduced in 1921 when the U.S. Bureau of Public Roads built a section on the Columbia Pike near Arlington, VA. Since then, CRCP has become standard practice in several states and many European countries. Over the years, various lessons learned through research and practical experience have contributed to improved design methods, material selection and construction practices.
CRCP Design Recommendations:
- A minimum of 0.6 percent reinforcing steel (based on the pavement cross-sectional area) is recommended to control transverse crack development in the 3 to 6 ft. range. Exceptions should be made only where experience has shown that a lower percentage of steel has performed satisfactorily. In areas where periods of extreme low temperature (average minimum monthly temperatures of 10° F or less) occur, the use of a minimum of 0.7 percent steel is recommended.
- Use deformed steel bars that meet the requirements set out in AASHTO Specifications, Part I, AASHTO M31 (carbon-steel), M42 (rail-steel) or M53 (axlesteel). The tensile requirements should conform to ASTM International Grade 60. Alternately, ASTM A615 or A996 deformed bars may be used.
- The recommended position of the longitudinal steel is between 1/3 and ½ of the depth of the pavement as measured from the surface. The minimum concrete cover should be 3½ inches. For pavements thicker than 11 inches, several states have begun to use two layers of longitudinal steel
Design Options for Maximizing CRCP Longevity:
- Wider outside lane (12′ to 14′) – moves truck wheels away from edge joint
- Tied CRCP shoulder – same thickness as pavement (can be used for a future lane and during lane closures or traffic diversions)
- Stabilized base (non-eroding) – to maintain good slab support
- Transverse reinforcing steel – in conjunction with adequate tie-bars between lanes
- Built-in centerline joint – to minimize random longitudinal cracking
Jointed Plain Concrete Pavement
JPCP contains enough joints to control the location of all the expected natural cracks; the design assumption is the concrete cracks at the joints and not elsewhere in the slabs. Jointed, plain pavements do not contain steel reinforcement. However, there may be plain steel bars at transverse joints and deformed steel bars at longitudinal joints. The spacing between transverse joints is typically about 15 feet for slabs 7 to 12 inches thick. Jointed plain concrete pavements (JPCP) are formed using sections of concrete joined using steel dowels. These dowels are typically coated using an epoxy or other material. For more information please visit:
Jointed Reinforced Concrete Pavement
JRCP contains steel mesh reinforcement (sometimes called distributed steel). In jointed reinforced concrete pavements, designers increase the joint spacing purposely, and include reinforcing steel to hold together intermediate cracks in each slab. The spacing between transverse joints is typically 30 feet or more. In the past, some agencies used a spacing as great as 100 feet. During construction of the interstate system, most agencies in the Eastern and Midwestern U.S. built jointed-reinforced pavement. This system is less commonly used than CRCP or JPCP.