30 June 2001
the economics involved. In certain instances, reinforcement will be required to control cracking that may
occur in plain concrete pavements without any reduction in thickness requirements.
REDUCED THICKNESS DESIGN - ARMY AND AIR FORCE.
a. General. The greatest use of reinforcement to reduce the required plain concrete pavement
thickness will probably be to provide a uniform thickness for the various types of traffic areas as different
structural conditions of the base pavement. Since these changes in thickness cannot be made at the
surface, reinforcement can be used to reduce the required thickness and thereby avoid the necessity for
removal and replacement of pavements or overdesigns. There are other instances in which
reinforcement to reduce the pavement thickness may be warranted and must be considered, but the
economic feasibility for the use of reinforcement must also be considered. The design procedure
consists of determining the percentage of steel required, the thickness of the reinforced concrete
pavement, and the maximum allowable length of slabs. In addition, a computer program discussed in
Chapter 1 may be used for the design of reinforced concrete pavement.
b. Determination of Required Percent Steel and Required Thickness of Reinforced Concrete
Pavement. It is first necessary to determine the required thickness of plain concrete pavement using the
design loading and physical properties of the pavement and foundation. When the reinforced concrete
pavement is to be placed on stabilized or nonstabilized bases or subgrades, the procedure outline in
Chapter 12 will be used to determine the thickness of plain concrete. The thickness of plain concrete is
then used to enter Figure 13-1 to determine the required percent steel and the required thickness of
reinforced concrete pavement. Since the thickness of reinforced concrete and percent steel are
interrelated, it will be necessary to establish a desired value of one and determine the other. The
resulting values of reinforced concrete thickness and percent steel will represent a reinforced concrete
pavement that will provide the same performance as the required thickness of plain concrete pavement.
In all cases, when the required thickness of plain concrete pavement is reduced by the addition of
reinforcing steel, the design percentage of steel will be placed in each of two directions (transverse and
longitudinal) in the slab. For construction purposes, the required thickness of reinforced concrete must
be rounded to the nearest full- and half-inch increment. When the indicated thickness is midway
between full- and half-inch, the thickness will be rounded upward.
c. Determination of Maximum Reinforced Concrete Pavement Slab Size. The maximum length or
width of the reinforced concrete pavement slabs is dependent largely upon the resistance to movement
of the slab on the underlying material and the yield strength of the reinforcing steel. The latter factor can
be easily determined, but very little reliable information is available regarding the sliding resistance of
concrete on the various foundation materials. For this design procedure, the sliding resistance has been
assumed to be constant for a reinforced concrete pavement cast directly on the subgrade, on a
stabilized or nonstabilized base course, or on an existing flexible pavement. The maximum allowable
width W or length L of reinforced concrete pavement slabs will be determined from the following: