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

TECHNICAL PAPER 89-03 -- Benefits of Using Dowel Bars
Over the past few years, Pavement Division personnel have
reviewed several sections of undoweled PCC pavements. In
general, these pavements have experienced a level of
deterioration due to faulting that is significantly greater
that found in comparable sections of doweled PCC pavements.
finding has led to a concern over the design and construction
than
This
of
undoweled pavement sections.
to illustrate the benefits
The purpose of this brief paper
of using dowels on jointed PCC
is
pavements,
of trucks.
particularly on those routes carrying a large number
For jointed PCC pavements to perform satisfactorily, traffic
loads must be effectively transferred from one slab to the next.
Without adequate load transfer, the pavement is subjected to a
variety of distresses, such as pumping, faulting, and corner
breaks. There is considerable disagreement on how load transfer
should be obtained. One school of thought is to rely on
aggregate interlock in combination with short joint spacings,
skewed joints, and stabilized subbases. The other school of
thought is to rely on load transfer devices, such as dowel bars.
Aggregate interlock is ineffective at crack widths greater than
0.035 inch. A smaller crack width, generally 0.025 inch, is
considered necessary for satisfactory long-term performance of
undoweled pavements. An Iowa DOT study"' of undoweled pavements
concluded that "from measurements of joint openings it appears
doubtful that aggregate interlock is maintained even by joints
spaced at 20 ft." When measured beneath the sawed portion of the
joint, over 90% of the joints had crack widths in excess of 0.06
inch. In order to limit crack widths to 0.035 inch over a
temperature range of 60-80 Fahrenheit degrees, joint spacings in
the range of 6 to 11 feet are'needed. Such a spacing is not
considered practical. Properly sized dowels, on the other hand,
provide effective load transfer at reasonable joint spacings.
Maximum joint spacings of 15-20 ft. and 30-40 ft. are recommended
for plain and reinforced pavements respectively.
The use of dowels has been shown to reduce faulting. A Florida
DOT study'2' concluded that "doweled contraction joints fault less
than non-doweled contraction joints." A Georgia DOT studyc3' of a
project on I-85 found that "dowel bars were effective in reducing
the faulting at the contraction joints." The Wisconsin DOT
conducted a condition surve of their Interstate system.
the findings of this studyc4 T
One of
was that "building nonreinforced
concrete pavements with additional thickness (2-3 inches) in lieu
of using positive load transfer devices (dowel bars) at
transverse contraction joints is not successful in preventing or
reducing joint faulting to an acceptable level during a
pavement's life." Faulting at the joints was notably absent
3.2.2