Jointed reinforced concrete pavements

Extensive studies have been carried out in the past to determine the amount of steel required in reinforced slabs. The principle adopted was that an increase of the amount of steel reinforcement limits the severity of cracking that may appear and reduces the number of transverse joints. 

The amount of reinforcement required in reinforced concrete slabs is best determined by the formula or procedure given in the pavement design methodology adopted. 

For information purposes, the minimum steel quantity required can be calculated by the following equation (Yoder and Witczak 1975)  

From the above equation, it is evident that the quantity of steel is dependent on the geometric dimensions of the slab, as well as the tensile strength of the steel. As the slab length (as well as the width) increases, greater amount of steel is required. 

The quantity of steel reinforcement in the case of jointed reinforced pavements is placed either in the longitudinal direction (the most common case nowadays) or in both directions in the form of a mesh. In the first case, some steel bars are also placed in the transverse direction simply to withhold the reinforcement in the longitudinal direction. 

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Depending on the existence (or non-existence) of reinforcement, rigid pavements are divided into four types of pavements (a) unreinforced concrete pavements (URCPs), (b) jointed reinforced concrete pavements (JRCPs), (c) CRCPs and (d) CRCPs with asphalt surfacing layer, formerly known as composite rigid pavements. 

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.)...

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). 

In an unreinforced concrete slab, the contraction joints are spaced approximately every 4 to 5 m, depending on the slab thickness and type of aggregate. In a jointed reinforced concrete slab, contraction joints are typically spaced every 20 to 25 m, depending on the amount of reinforcement. The designer is advised to strictly follow the instructions of the pavement methodology used with regard to the spacing of the contraction joints. 

Fibre-reinforced concrete may be used in unreinforced as well as reinforced concrete pavements. The use of steel fibre-reinforced usually does not cause reduction of reinforcement required, it simply allows to increase the spacing between joints, which is advantageous. 

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

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. 

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. 

E.K. Schrader, Fiber reinforced concrete pavements and slabs A state-of-the-art report , in S.P. Shah and A. Skarendahl (eds) Steel Fibre Concrete, US-Sweden Joint Seminar, Stockholm, 1985, pp. 109-131. 

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). 

As for jointed reinforced pavement, the thickness of the reinforced concrete slab is determined by the following equation ... 

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. 

Break (or crack) and seat is a technique to reduce the effective length of the concrete slab so that the horizontal strains resulting from the thermal expansion are reduced and evenly distributed. The above reduces the potential for reflecting cracking to occur. The break and seat technique is normally applied to unreinforced pavements but it may be applied to jointed reinforced pavements as well. 

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