Continuously reinforced concrete
pavement (CRCP)
Continuously reinforced concrete
pavement (CRCP) is the major type
of highway pavement used for the expressways
in the urban parts. It is favoured because of its increased ride quality,
minimal maintenance, and extended
service life.It does not require any contraction joints. Transverse cracks are allowed to form but are held tightly together with continuous reinforcing steel.CRCP may sometimes experience
early failure of ride quality owing to
surface spalling adjacent to full depth
cracks when certain siliceous river
gravels are used. This results in the need to repair or apply an overlay
to a number of damaged sections.Research has shown that the maximum allowable design crack width is about 0.5 mm (0.02 inches) to protect against spalling and water penetration (CRSI, 1996). Cracks typically form at intervals of 1.1 - 2.4 m (3.5 - 8 ft.).No. 5 and No. 6 deformed reinforcing bars are used. Reinforcing steel usually constitutes about 0.6 - 0.7 percent of the cross-sectional pavement area and is located near mid-depth in the slab.

DESIGN RECOMMENDATIONS
1)Concrete Thickness. Generally the slab thickness is taken as same as the thickness of a jointed concrete pavement unless local performance has shown thinner pavements designed with an accepted design process to be satisfactory.

2)Reinforcing Steel:
a)Longitudinal Steel:based on the pavement cross sectional area, 0. 6 percent is recommended to aid transverse crack development in the range of 8 feet.
b) Deformed steel bars are recommended. The spacing of the longitudinal steel is not less than 4 inches or 2 1/2 times the maximum sized aggregate, whichever is greater.
c)) The recommended position of the longitudinal steel is between 1/3 and 1/2 of the depth of the pavement from the surface.
d) areas where corrosion is a problem, epoxy coated reinforcing steel is recommended.
e)When splicing longitudinal steel, the recommended minimum lap is 25 bar diameters with the splice pattern being either staggered or skewed.
f) Plan details or specifications are needed to insure sufficient reinforcing at points of discontinuity.

Transverse Reinforcing and Tiebars
If transverse reinforcement is included, it should be #4, #5, or #6 grade 60 deformed bars. transverse reinforcing reduces the risk of random longitudinal cracks opening up and thus reduces the potential of punch-outs. tiebars should be placed in longitudinal joints where transverse steel is omitted.

3.Bases
The base design should provide a stable foundation and should not trap free moisture beneath the pavement.Positive drainage is recommended. The friction between the pavement and base plays a role in the development of crack spacing in CRCP. Polyethylene sheeting should not be used as a bond breaker unless the low pavement/base friction is considered in design.

4.Subgrades
CRCP is not recommended in areas where subgrade distortion is expected and Subgrade treatment may be used for poor soil conditions.

5.Joints
Longitudinal joints are necessary to relieve stresses caused by concrete shrinkage and temperature differentials in a controlled manner and should be included when pavement widths are greater than 14 feet. Most commonly used Terminal joints are the wide-flange (WF) steel beam which accommodates movement, and the lug anchor which restricts movement.

For more details read:
http://fhwa.dot.gov/legsregs/directives/...508014.htm