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300 Rigid Pavement Design
301 Design Parameters
ODOT's method for the design of rigid pavement limits the designer to prescribed input
parameters. The input values prescribed are based on Ohio materials and ODOT Specifications.
301.1 Modulus of Rupture
Modulus of rupture, as determined under a breaking load, measures the flexural strength or
extreme fiber stress, of the concrete slab. There are many ways to determine the modulus of rupture and
each way will give slightly different results, however, each method can be correlated to the measure
defined for use in the AASHTO/ODOT method. The modulus of rupture used in ODOT's pavement
design method is the 28-day, third-point loading test as defined by ASTM C 78. All rigid pavement
designs should use a modulus of rupture of 700 psi, as shown in Figure 301-1. Average values obtained
through beam breaks performed as part of C&MS requirements for opening to traffic should not be used
directly for design purposes, as this test is defined by ASTM C 293 as center-point loading, and is
generally done as early as 5 days.
301.2 Modulus of Elasticity
The modulus of elasticity of concrete is a function of the strength, age, aggregate properties,
cement properties, and type and size of the specimen tested as well as the rate of loading during the test.
Furthermore, there are various methods used to determine the modulus of elasticity. ODOT's method for
rigid pavement thickness design is not highly sensitive to the value used for modulus of elasticity. Based
on values obtained by ODOT research, a modulus of elasticity of 5,000,000 psi should be used for all
rigid pavement designs. The modulus of elasticity is shown in Figure 301-1
301.3 Load Transfer Coefficient
The load transfer coefficient (J) is a factor used in rigid pavement design to account for the ability
of a concrete pavement to distribute (transfer) load across discontinuities, such as longitudinal and
transverse joints. Load transfer devices, aggregate interlock, widened lanes, and the presence of tied
concrete shoulders all have an influence on this value. J factors are listed in Figure 301-1.
301.4 Composite Modulus of Subgrade Reaction
The composite modulus of subgrade reaction (k
stiffness or subgrade modulus of resilience, as discussed in Section 203.1, and the stiffness, or elastic
modulus, and thickness of the subbase material. The pavement design process requires the designer to
choose the subbase prior to determination of the required slab thickness. The values for elastic modulus
of the subbase for ODOT materials are listed in Figure 301-1.
determines the composite modulus of subgrade reaction.
A 6 inch (150 mm) granular base, item 304, is recommended as a subbase under all concrete
pavements to prevent pumping.
chemically stabilized subgrade. For very low traffic situations (less than 500,000 design ESALs) or on
non-stabilized granular subgrades, consideration may be given to eliminating the granular base.
301.5 Loss of Support
Loss of support (LS) is included in the design of rigid pavements to account for the potential loss
of support arising from subbase erosion or differential vertical soil movements. The potential of a material
to pump is an indication support may be lost. Loss of support is treated in the design procedure by
reducing the composite modulus of subgrade reaction. Figure 301-1 lists the LS factors to be used for
ODOT materials.
July 2014
) represents the combined effect of the subgrade
c
The granular base is required for concrete pavement built over a
Figure 301-2 is a nomograph that
300-2
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