Thickness determination of slab all cases

The thickness determination of the concrete slab in a rigid pavement regardless of being unreinforced or reinforced is carried out as follows  

If the slab is going to be placed directly on the subgrade (i.e. no sub-base), the composite modulus of subgrade reaction, k value, is defined by using the equation 

Other input data for the determination of the concrete slab are as follows elastic modulus of concrete, E, mean concrete modulus of rupture, (three-point bending test), load transfer coefficient, J (from Table 2.6 of AASHTO 1993), drainage coefficient, Cj (coefficient similar to the one used in flexible pavements), design serviceability loss (APSI), estimated future traffic, Wjg (as determined in flexible pavements but using equivalency coefficients for rigid pavements), the overall standard deviation, (usually 0.35), and the reliability, R (as determined in flexible pavements). 

The approach to consider the effects of swelling and frost heave in rigid pavement design is almost identical to that for flexible pavements. In fact, the total environmental serviceability loss caused by swelling and frost heave (APSIjw.fh) calculated and is then used to predict its effect on performance period. For more details, see AASHTO (1993). 

Finally, it is noted that, in this methodology, unlike the UK methodology, there is no adjustment (increase) of the slab thickness owing to the absence of concrete shoulder. 

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