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

SlJbJect- Dowel Bar Inserters Date
From
Chief, Pavement Division
Uashington, D.C. 20590-0001
To: Regional Federal Highway Administrators
Federal Lands Highway Program Administrator
Attention: Pavement Engineers
Memorandum
MAR 619?30
Reply to
Attn 01. HHO-12
Attached for your information is a copy of a report prepared by the Wisconsin
Department of Transportation (WDOT) ent itled *'Dowel Bar Placement: Mechanica 1
Insertion Versus Basket Assemblies." This study found that dowel placement
accuracy
accuracy
achieved
achieved
with the mechanical inserters equaled or surpassed the
with basket assemblies. As a result, the WDOT now permits
the use of mechanical dowel bar inserters on construction projects.
Wisconsin's evaluation of dowel placement accuracy was based on their
specification, which permits an alignment tolerance of l/2-inch per dowel.
This is slightly greater than the l/4-inch per foot (3/8-inch per dowel)
recommended in our May 17, 1989, Technical Paper 89-03, Benefits of Using
Dowel Bars. Wisconsin is using a joint spacing of 12-13-19-18 feet and has
not reported any distress which would indicate dowel alignment problems. As
pointed out in Technical Paper 89-03, we are continuing to evaluate the
specification tolerances for dowel al igrunent.
We concur with the WDOT's conclusion that: "The initial set-up of the dowel
bar inserter with respect to depth of dowel placement is critical at the start
of each project, and dowel depths should be verified by probing through the
fresh concrete." We also recommend that when either baskets or inserters are
used, the location of the dowels in the completed pavement be verified using
metal detectors, pachometers, and cores.
If you have any questions or comments, please contact Mr. John Hallin at
366-1323.
3.5.1