Minne-ALF Project Overview and Retro-Fit Dowel Study Results

A laboratory-based linear loading pavement test stand, the Minnesota Accelerated Loading Facility (Minne-ALF) simulates the passage of heavy traffic loads moving at speeds up to 65 kph (40 mph) over small, full-scale pavement test slabs. Hydraulic actuators control a rocker beam, which simulates loads. Researchers simulated the passage of 40-kN (9-kip) single-wheel loads at a rate of 172,000 per day, although wheel loads up to 100 kN (22 kips) can be simulated at varying speeds. Full-axle simulations are possible with frame modifications. Concrete slabs were cast and dowels were installed in slots across cracks/joints. Test variables included joint fact texture, repair backfill material, and dowel material and length. Test outputs included measurements of load transfer efficiency and differential deflection across the joint/crack. The effect of joint/crack face texture was great when the joint/crack remained tight. Load carrying performance was improved using Speed Crete 2028 in place of 3U18 concrete backfill with similar joint and dowel bars. Load transfer was unaffected by the use of stainless steel-clad dowel bars in lieu of epoxy-coated dowel bars. Researchers recommend additional testing to examine the effects of dowel length and dowel materials.