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

the dowel is vibrated downward, and the logical location for
voids is above the dowel, so it is likely that all voids were
detected on the inserter projects. However, on the basket
projects the concrete flows downward past the dowel, and the
logical location for voids is underneath the dowel. Since on,,
the top of the dowel was inspected for this study, it is possible
that the void problem may be understated for the basket projects
due to undetected voids beneath the dowels. Further coring needs
to be performed on basket projects to assess the extent of this
problem.
Voids of this magnitude could affect the load transfer capacity
of the dowels, so improvement in this area is needed. The amount
of vibration used on the inserter needs to be increased slightly,
but caution must be exercised to avoid using excessive vibration
which may damage the concrete. In conclusion, quality control
coring should be performed on inserter and basket projects
constructed in the near future to assess the progress in solving
this problem.
plissina Dowels: Another problem unique to the dowel bar inserter
is that sometimes dowel bars are missing completely. This is
difficult to inspect for, when the dowels are immediately buried
in the concrete, instead of being laid out on the grade ahead of
the paver. At one test joint on the USH 18/151 project, all of
the dowels for the joint were missing. Using the xnagnetic rebar
locator, it was determined that all of the dowels were present in
the two adjacent joints, but the 24 missing dowels were not found
anywhere between the adjacent joints. On the South Madison
Beltline project, three dowels were missing from one test joi
and one dowel was missing from another test joint. The three
missing dowels were located at the edge of the pavement on the
opposite side of the road from where the inserter distribution
carriage is loaded. In that instance, it is likely that an
insufficient number of dowel bars were loaded into the
distribution carriage for that joint. The single missing dowel
was located in the first position on the same side of the road
where the distribution carriage is loaded. In that instance, it
is possible that the missing dowel resulted from a misfeed or jam
of the distribution system.
If every joint on the three inserter projects in this study was
to be checked with a rebar locator, it is doubtless that
additional occurrences of missing dowels would be identified, but
the extent of the problem is currently not known. However, if
the frequency of missing dowels noted at the test joints is an
accurate indicator, then the incidence of missing dowels is
probably relatively rare and isolated. This issue presents
another good justification for having a magnetic rebar locator
available on future inserter projects. The paving inspector
cannot possibly observe the performance of the inserter on every
joint. It would be good practice to make random checks with the
rebar locator to verify dowel presence, and to make more
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