Highway Engineering

where thin wearing course systems (TWCS) are acceptable. These have noise

reducing properties and lend themselves to the application of further asphalt

overlays during the pavement’s life.

8.3.2 Continuously reinforced concrete pavements (CRCP)

A continuously reinforced concrete pavement is one in which the reinforcement

is at a sufficiently high level that the slab can withstand the incident stresses

without requiring the use of transverse joints. This slab type will require less

maintenance than a jointed pavement and will span more effectively over areas

where the underlying soil is weak. A CRCP ensures that a uniformly high stress

level is maintained within the slab.

Cracks will develop within continuously reinforced slabs. This, however, will

not give rise to concerns provided they are neither too wide nor too close

together. Cracks should be no closer than 1.5 m but no further apart than twice

this distance, as this would result in the cracks being at a width that would

require significant maintenance. There is a strong likelihood that cracks less than

1.5 m apart will result in punching failure.

In the past there has been no generally accepted methodology for the design

of continuously reinforced concrete slabs. Typically, slabs were designed as

jointed reinforced, with the proportion of reinforcement fixed at a typical level

of 0.6%. The thickness could then be reduced to allow for the longer design life

arising from use of the continuously reinforced slab.

Most recently, HD 26/01 details slab designs for both rigid and rigid com-

posite pavements. ‘Rigid’ denotes continuously reinforced concrete pavements

(CRCP) with either no surfacing or a thin wearing course system with a

minimum depth of 30 mm. Where noise levels are high due to the intensity of

248 Highway Engineering

Basic design slab thickness (mm)

40

35

30

25

20

150 250 350

Additional slab

thickness (mm)

Figure 8.15

Additional concrete

slab thickness if 1 m

tied shoulder not

available (HD 26/01)

(DoT, 2001).