Design principle

Welded wire fabric or deformed bars or steel fibres are used for reinforcement purpose (Swanlund and Vanikar 2002, IRC:SP:46 1997). Reinforcement in the concrete slabs is mainly provided for counteracting the shrinkage (and associated cracks) due to temperature and moisture changes (PCA 1995). It does not allow crack to become wider (Austroads 2004), and thereby ingress of water and grit is prevented (IRC:101 1991).

Since, the reinforcement provided in concrete pavement is not for contributing towards flexural strength, therefore, its position in the concrete slab is not important. Generally reinforcement is placed 50 mm below the surface (IRC:58 1988). The basic slab thickness is designed as per the plain cement concrete pavement design procedure 1 , however, due to provision of steel reinforcement, there is an effective increase of the slab thickness due to provision of steel reinforcement (IRC:101 1991).

The requirement of steel reinforcement can be calculated on the basis of maximum force that can overcome the frictional force between the concrete slab and the layer just below it. The shrinkage stress is maximum at the middle, and less at the edges or corners. Though theoretical equations have been developed for design of reinforcement, generally, some empirical relations are used to estimate the amount of reinforcement (Austroads 2004, PCA 1995, IRC:101 1991). For JRCP longitudinal steel reinforcement is about 0.15 to 0.25% of the cross-sectional area of the slab, for CRCP it is about 06 to 1.0% (Swanlund and Vanikar 2002, IRC:101 1991). For steel fibre reinforcement the amount of fibre used is generally 0.75 to 1.5% (IRC:SP:46 1997). Nominal transverse reinforcement is provided to control transverse cracking in both JRCP and CRCP.