National Concrete Consortium (NCC), The National Concrete Pavement Technology Center (CP Tech Center), dowel manufacturers, and the American Concrete Pavement Association (ACPA) have been working with the Construction Technology Laboratories, Inc. (CTLGroup) to develop specifications that can be used by manufacturers and agencies to guide the development and implementation of more efficient and durable dowels for concrete pavements.
Current AASHTO M254 and T253 specifications were developed decades ago and are directly applicable only to 1.25-in. diameter epoxy-coated steel dowels. The need for specifications that can quantify the potential performance benefits of these new and improved products have driven industry innovations featuring:
⢠Different materials
⢠Different structural shapes
⢠Different dowel coatings
Data from these tests are being compiled and analyzed for incorporation in a new set of âuniversalâ dowel specifications that are built on the current AASHTO M254 and T253 specifications.
One key component of dowel specifications is their ability to evaluate the structural behavior of joints containing different dowel products. It has been recognized that a new test was needed to evaluate dowel groups rather than single dowels because different dowels could have different optimal installation configurations due to differences in size, shape, and component materials and these could not be adequately evaluated using a single-dowel test. This led to a proposal to modify the current T253 structural test to include a four-foot-wide test specimen with dowel groups in each joint (rather than the single dowel in each joint for the current T253 test).
The different specimen configuration required different loading (a simulated 9000-lb wheel load at the slab corner instead of the original 4000-lb distributed load). The different loading configuration and specimen shape meant that joint deflections would be different than in the original T253 test, even if 1.25-in. diameter epoxy-coated steel dowels were used. Analytical models were used to estimate the joint deflections for both test protocols using the standard epoxy-coated dowel, but testing was needed to validate and calibrate those analytical models for âreal-worldâ conditions.
This testing was accomplished in May 2020 at CTLGroup under ACPA supervision, with funding provided by CP Tech Center.
Data from these tests are being compiled and analyzed for incorporation in a new set of âuniversalâ dowel specifications that are built on the current AASHTO M254 and T253 specifications.
The new specifications have been developed with the input of various NCCÂ member agencies, ACPA staff (national and chapter/state), and dowel manufacturers. It is anticipated that the new specifications will be released for wider review and comment early summer 2020, with possible promotion for American Association of State Highway and Transportation Officials (AASHTO) adoption soon afterward. (Special thanks to Mark Snyder, Ph.D., P.E., Former President-ISCP, for compiling this report.)