Pavements and slabs on grade

As stated earlier, slabs on grade constitute about 60% of the FRC production. While these are not strictly structural applications, a number of rational design methods have been developed for FRC pavements and slabs on grade, for both steel and synthetic fibres. It should, however, denoted that the design methods referred to here have been developed by the fibre manufacturers themselves. While the principles of these design methods may be generalized, the numerical constants used in these methods are only applicable to the particular fibre type for which the method was originally developed. 

2 The observation that fibre reinforcement of slabs avoids their brittle collapse once the first crack appears, considerable stress redistribution begins due to the ability of the fibres to tie the cracks together. Thus the slabs can carry further loads until a collapse mechanism occurs when the fibres are no longer able to bridge the cracks effectively. 

In designing an FRC slab, the appropriate equations mentioned in [1] above are used, but modified for the toughness, or the residual (post-cracking) tensile or flexural strength of the FRC. It should be noted that this modification depends on the specific test procedure used to characterize the FRC (see Chapter 6), and again may not be easy to generalize. 

It is assumed that the onset of cracking at the top of the slab is the limiting design criterion. Since fibres do not particularly affect the cracking stress, the negative bending moment capacity, Mn, is simply calculated as 

The Re,2 and Re,3 values are the equivalent flexural strengths the fjj and fej values are the residual strengths at deflections of 2 mm and 3 mm, respectively. 

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