Using the Minnesota Accelerated Loading Facility to Test Retrofit Dowel Load Transfer Systems

Abstract

The Minnesota Accelerated Loading Facility (Minne-ALF) is a laboratory-based, linear-loading, pavement test stand that simulates the passage of heavy loads moving at speeds up to 65 km/h over small, full-scale pavement test slabs. Moving wheel loads are simulated using a rocker beam controlled by hydraulic actuators. In this study, the passage of 40-kN single wheel loads was simulated at a rate of 172,800 loads per day. Demonstration tests were performed to (a) determine the effects of selected design and construction variables on retrofit dowel load transfer system performance, (b) measure the variability of Minne-ALF test results, (c) demonstrate the general usefulness of the Minne-ALF, and (d) identify the need for any additional test system modifications. Concrete slabs specimens were cast and dowels were installed in slots across cracks and formed joints. Test variables included joint face texture, repair backfill material, and dowel material and length. Test outputs included measurements of load transfer efficiency and differential deflection across the joint or crack. The effect of joint or crack face texture was great when the joint or crack remained tight. Load-carrying performance was improved by using Speed Crete 2028 in place of Minnesota Department of Transportation specification 3U18 (preproportioned bag mix) concrete backfill with similar joints and dowel bars. Load transfer was unaffected by the use of stainless steel–clad, fiber-reinforced plastic or grout-filled tubes in lieu of epoxy-coated structural steel dowel bars. Additional testing is recommended to examine the effects of dowel length and materials. This test program demonstrated the usefulness of the Minne-ALF; additional testing is planned.

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References

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