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

Fidh'X TECHSiC.AL .AL1L~!SC!?'r' T SO40.3r3
Sovember 30, 1990
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While the above equation can be used to estimate
anticipated _- joint movements, it may be worthwhile
physically measure joint movements in existing
to
pavements. These measurements could provide
designer with more realistic design inputs.
the
TABLE 2. TYPICAL VALUES FOR PCC COEFFICIENf OF
SHRINKAGE (a) (11
Indirect Tensile PCC Coeff. of
Strength (psi) Shrinkage (in./in.)
ix; (or less)
500
600
700 (or greater)
0.0008
'0.0006
0.00045
0.0003
0.0002
-- .-. -
(2) Par plain concrete slabs, a maximum joint spacing of 15 feet
is reconunended. Longer slabs frequently develop transverse
cracks. It is recognized that in certain areas, joint
spacings greater than 15 feet have performed satisfactorily.
The importance of taking local experience into account when
selecting joint spacing (and designing pavements in general)
cannot be overstated. Studies have shown that pavement
thickness, base stiffness, and climate also affect the
maximum anticipated joint spacing beyond which transverse
cracking can be expected. 'Research indicates that there is
a general relationship between the ratio of slab length (L)
to the radius of relative stiffness (C) and the amount of
transverse cracking [2]. This research shows that there is
an increase in transverse cracking when the ratio L/C
exceeds 5.0. Further discussion is provided in Attachment
1.
(3) For reinforced concrete slabs, a maximum joint spacing of 30
feet is recommended. Longer slab lengths have a greater
tendency to develop working mid-panel cracks caused by the
rupture of the steel reinforcement. Studies have also shown
that, as the joint spacing increases above 30 feet, the rate
of faulting increases and joint sealant performance
decreases [4].
3.1.4