30 June 2001
(1 inch), will be repaired by cold planing, localized patching, or the application of a leveling course
using bituminous concrete, sand-asphalt, or a similar material.
c. Nonrigid Overlay. When a flexible overlay is used, no special treatment of the surface of
the existing pavement will be required other than the removal of loose material. When an all-
bituminous concrete overlay is used, the surface of the existing pavement will be cleaned of all
foreign matter. Spalled concrete, fat spots in bituminous patches, and extruded soft or spongy
joint seal material on rigid pavements will be removed. Joints or cracks less than 25 millimeters
(1 inch) wide in an existing rigid pavement will be filled with joint sealant. Joints or cracks that are
25 millimeters (1 inch) or greater in width will be cleaned and filled with an acceptable bituminous
mixture (such as sand-asphalt) which is compatible with the overlay. Leveling courses of
bituminous concrete will be used to bring the existing pavement to the proper grade when required.
Prior to placing the all-bituminous concrete overlay, a tack coat will be applied to the surface of the
CONDITION OF EXISTING CONCRETE PAVEMENT.
a. General. The support that the existing rigid pavement will provide to an overlay is a
function of its structural condition just prior to the overlay. In the overlay design equations, the
structural condition of the existing concrete pavement is assessed by a condition factor, C. The
value of C should be selected based upon a condition survey (ASTM D 5340) of the existing rigid
pavement. Interpolation of C values between those shown below may be used if it is considered
necessary to more accurately define the existing structural condition. As an alternative,
Figure 17-1 may be used to select the C value for plain concrete or nonrigid overlays. This figure
relates a structural condition index (SCI) and C. The SCI is that part of the pavement condition
index (PCI) related to structural distress types as deduct values. To determine SCI values, a
condition survey is conducted according to ASTM D 5340. However, rather than calculating the
PCI, an SCI is calculated by subtracting the deduct values for corner breaks, longitudinal,
transverse and diagonal cracking, shattered slabs, spalling along joints, and spalling corners from
b. Rigid Overlay. The following values of C are assigned for the following conditions of plain
and reinforced concrete pavements.
(1) Condition of existing plain concrete pavement:
C = 1.00 - Pavements in the trafficked areas are in good condition with little or no
structural cracking because of load
C = 0.75 - Pavements in the trafficked areas exhibit initial cracking because of
load but no progressive cracking or faulting of joints or cracks
C = 0.35 - Pavements in the trafficked areas exhibit progressive cracking because
of load accompanied by spalling, raveling, or faulting of cracks and
(2) Condition of existing reinforced concrete pavement.