UFC 3-260-03

15 Apr 01

ho = thickness of rigid overlay pavement, millimeters (inches)

C = coefficient representing condition of rigid base pavement

hb = thickness of rigid base pavement, millimeters (inches)

(2) If a bond-breaker course was used between the rigid overlay and the rigid base pavement,

the hE value of the combined overlay section can be computed from the following equation for no bond

between the overlay and the base pavement:

(*h*o ) 2 % *C *(*h*b ) 2

(eq 6-4)

No credit is given to the thickness of the bond breaker if less than 102 millimeters (4 inches). If the thick-

ness of the bond breaker is greater than 102 millimeters (4 inches), then the pavement will be evaluated

as a composite pavement.

(a) The value of C in equations 6-3 and 6-4 depends on the condition of the existing rigid

base pavement. The following C values are recommended:

C = 1.00 for base pavement in good condition

C = 0.75 for base pavement having a few initial cracks due to loading, but no progressive cracks

C = 0.35 for badly cracked base pavement

Other values for C can be used; however, since guidance is not provided, engineering judgment must be

applied when selecting values other than those listed above.

(b) After the hE value of the combined section has been determined from equation 6-3 or

6-4, the method of evaluating a rigid overlay on a rigid base pavement is the same as for a plain concrete

pavement. The flexural strength (R) to use would be the weighted average of the overlay and base pave-

ment strengths, determined as follows:

(eq 6-5)

where

ho = thickness of overlay

Ro = flexural strength of overlay

hb = thickness of base slab

Rb = flexural strength of base slab

c. Evaluation Example. Determine an extended life evaluation in terms of passes for the C-130

aircraft at a gross weight of 61,236 kilograms (135 kips) on a type B traffic area consisting of a

152-millimeter (6-inch) base pavement and a 152-millimeter (6-inch) rigid overlay with no bond breaker.

6-9