Continuously reinforced concrete pavements

In the case of continuously reinforced pavements, the quantity of steel used normally ranges from 0.5% to 0.7% of the slab cross-sectional area, depending on the design method used. 

The reinforcement almost always is placed in the longitudinal direction and at the mid-depth of the specified thickness of the slab. When siliceous aggregates are used, the reinforcement is recommended to be located at a depth equal to one-third of the slab thickness, since it has been found to improve the crack pattern of the siliceous aggregate CRCPs (Hassan et al. 2005). 

The reinforcement is usually high-yield deformed steel bars (500 MPa) with diameter and spacing as defined by the design method employed. 

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Figure 5.2 A corrosion monitoring probe consisting of a reference eiectrode and an auxiliary electrode potted up in mortar in the process of installation into a continuously reinforced concrete pavement where corrosion monitoring is required due to the high level of chloride found in the mix water after laying several kilometres of concrete (Broomfield et a/., 2003) photograph. Courtesy BGB Projects Ltd.

Figure 14.1 Characteristic types of rigid pavements, (a) Unreinforced concrete pavement (URCP) (b) jointed reinforced concrete pavement (JRCP) (c.i) continuously reinforced concrete pavement (CRCP), without asphalt overlay (c.ii) CRCP, with thin asphalt overlay and (d) rigid pavement with continuously reinforced concrete base (CRCB) and asphalt overlay. (Adapted from Highways Agency, The Manual of Contract Documents for Highway Works [MCDHW], Volume 3 Highway Construction Details, Department for Transport. London Highways Agency, 2006c.)...

The provision of crack-relief layer was pioneered in the United States for use in jointed and continuously reinforced concrete pavements to minimize reflection cracking. 

Similarly, for continuously reinforced concrete pavements, the critical deflection (maximum deflection), D3, should have a maximum value as that given in Table 15.19, depending on the device used. 

Note JRC, jointed concrete pavements CRCP, continuously reinforced concrete pavement Benkel.. Benkelman beam Dynafl., Dynaflect RR4 S,Road Rater 400 and S10 measurements were made at 4.5 kN and 8-10 Hz RR 2000. Road Rater 2000 measurements were made at 36 kN and IS Hz FWD, falling weight deflectometer measurements were made at 40 kN. 

Similar predictive equations for smoothness degradation have also been developed for HMA overlays of rigid pavements, jointed reinforced concrete pavements (JRCPs) and continuously reinforced concrete pavements (CRCPs), which can be found in the MEPDG manual (AASHTO 2008). 

Figure 31.7 (Top) FRP rebar for continuously reinforced concrete pavements. (Bottom) FRP dowel bars for conventional concrete pavement. (Photos courtesy of CFC-WVU).

The CRCPs with asphalt surfacing layer may be further distinguished into CRCPs with thin asphalt overlay (minimum thickness of 30 mm) or CRCPs with an asphalt overlay of 100 mm. The latter is known as rigid pavement with continuously reinforced concrete base (CRCB) and asphalt overlay. 

A detailed procedure for designing rigid concrete pavements with jointed or continuously reinforced concrete slabs can be found in the AASHTO manual (AASHTO 1993). However, in the following paragraphs, a brief description for determining the thickness of the concrete slab in all cases (unreinforced or reinforced slabs) and the required quantity of reinforcement are given for the benefit of the reader. 

The methodology covers the design of jointed (unreinforced and reinforced), continuously reinforced and fibre-reinforced concrete pavements. The case of pre-stressed rigid pavement... 

For unreinforced and jointed reinforced type of concrete pavements, all types of joints are provided, while in the continuously reinforced pavements, only longitudinal (warping) joints are provided (see Figure 14.6). 

For continuously reinforced pavements (CRCP or CRCB), it has been assumed that no concrete slab maintenance or reinforcement will be required over the design period. As for the maintenance of thick or thin asphalt layers, it depends on the nature of the traffic. 

Hot asphalt surfacing overlay restores micro- and macro-texture and is the most suitable treatment for restoration of skid resistance of continuously reinforced pavement surface. All types of hot asphalts used in restoration of skid resistance of flexible pavements can be used, namely asphalt concrete for very thin layers, SMA and porous asphalt. 

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