chapter 3 rigid pavement - DOT On-Line Publications - Department ...

FHWA TECHNICAL ADV ISORY T 5080.
June 5, 1990
is recommended. Free moisture in a base or subgrade can
1,ead to slab edge-pumping, which has been identified as
one of the major contributors to causing or accelerating
pavement distress. Bases that will resist erosion from
high water pressures induced from pavement deflections
under traffic loads, or that are free draining to
prevent free moisture beneath the pavement will act to
prevent pumping. Stabilized permeable bases should be
considered for heavily traveled routes. Pavements
constructed over stabilized or crushed stone bases have
generally resulted in better performing pavements than
those constructed on unstabilized gravel.
The friction between the pavement and base plays a role
in the development of crack spacing in CRCP. Most
design methods for CRCP assume a moderate level of
pavement/base friction. Polyethylene sheeting should not
be used as a bond breaker unless the low pavement/base
friction is considered in design. Also, States have
reported rideability and construction problems when PCC
was constructed on polyethylene sheeting.
d. Subqrades. Continuously Reinforced Concrete Pavement is not
recommended in areas where subgrade distortion is expected
because of known expansive soils, frost heave, or settlement
areas. Emphasis should be placed on obtaining uniform and
adequately compacted subgrades. Subgrade treatment may be
warranted for poor soil conditions.
e. Joints
(1) Lonqitudinal Joints. Longitudinal joints are necessary
to relieve stresses caused by concrete shrinkage and
temperature differentials in a controlled manner and
should be included when pavement widths are greater than
14 feet. Pavements greater than 14 feet wide are
susceptible to longitudinal cracking. The joint should
be constructed by sawing to a depth of one-third the
pavement thickness. Adjacent slabs should be tied
together by tiebars or transverse steel to prevent lane
separation. Tiebar design is discussed in the FHWA
Technical Advisory entitled "Concrete Pavement Joints".
(2) Terminal Joints. The most commonly used terminal
treatments are the wide-flange (WF) steel beam which
accommodates movement, and the lug anchor which restricts
movement.
(a) The WF beam joint consists of a WF beam partially
set into a reinforced concrete sleeper slab
approximately 10 feet long and 10 inches thick. The
top flange of the beam is flush with the pavement
3.6.6
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