Page 327 - Planning and Design of Airports

Structural Design of Airport Pavements 285

• Shattered slab
• Shrinkage cracks
• Spalling (cracking, breaking, or chipping of joint/crack edges)
The SCI is estimated using standard pavement structural condi-
tion formulas based on empirical analysis that may be found in gen-
eral concrete structural evaluation references.
In the case when there are no visible or otherwise degradations in
structural condition, the FAA calls for the estimation of a cumulative
damage factor used (CDFU). For aggregate base layers, CDFU may be
estimated by Eq. (7-10).

L
CDFU = U when L < 075. L
.
075 L D U D (7-10)
.
= 1 when L 0 75 L
U D
where:
L = number of years of operation of the existing pavement
U
until overlay
L = design life of the existing pavement in years
D
For rigid pavement bases, CDFU is estimated using the FAAR-
FIELD software, based on the number of years the pavement has
been in use to date. Figure 7-14 illustrates the FAARFIELD output for
estimating CDFU for rigid pavement bases.

FIGURE 7-14 CDFU estimation for rigid pavement bases using FAARFIELD.