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Browsing by Author "Embacher, Rebecca A"

Now showing 1 - 3 of 3
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    Condition and Durability of Segmental Concrete Block Retaining Walls Along Roadways in Minnesota
    (2001-07-01) Embacher, Rebecca A; Schultz, Arturo E; Snyder, Mark B
    This research project assesses the nature and extent of premature deterioration of segmental concrete block retaining walls (SCBRWs) along roadways in the Minneapolis-St. Paul area. Researchers conducted a two-stage condition survey on 104 SCBRWs. The first stage, a general distress survey, focused on determining the type, severity, and extent of distresses present. The second stage, a peak winter survey, assessed the extent of snow/ice cover and exposure to winter sun. According to research results, only 7 percent of the SCBRWs surveyed were in poor or very poor condition. But researchers observed many distress types in 50 percent or more of the walls surveyed, including freeze-thaw damage, scaling, manufacturing flaws, and efflorescence. Freeze-thaw damage and scaling were most highly associated with decreases in overall wall condition. Efflorescence and freeze-thaw damage were found to be at least partly dependent upon SCBRW age and block manufacturer. Durability problems appear to be directly related to the lack of durability of the block units, which suggests problems with the use of inadequate mix designs, non-durable aggregate, and/or inadequate curing procedures. The report includes recommendations to address possible deficiencies in manufacturing processes and quality.
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    Minne-ALF Project Overview and Retro-Fit Dowel Study Results
    (1999-12-01) Snyder, Mark B; Embacher, Rebecca A
    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.
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    Refinement and Validation of the Hydraulic Fracture Test
    (2003-12-01) Embacher, Rebecca A; Snyder, Mark B
    This report describes the results of recent research efforts to improve the test. The hydraulic fracture index has been replaced by a model that predicts freeze-thaw test dilation as a function of the distribution of particle mass retained on various sieves after testing. This model was developed using data obtained from freeze-thaw and hydraulic fracture testing of 18 quarried carbonate and gravel aggregate sources, and the resulting correlation is exceptional (r-squared = 0.98). In addition, a large test chamber was developed to allow testing of aggregate samples five times larger than the original small chamber, thereby allowing aggregate durability characterization with a single test run. It is believed that the hydraulic fracture test is now ready for more broad-based validation testing and eventual widespread acceptance and implementation as an accurate screening tool for concrete aggregate freeze-thaw durability. Report describing the results of recent improvements to the Washington Hydraulic Fracture Test for concrete aggregate freeze-thaw durability. The test is believed to now be ready for validation testing and eventual wide-spread acceptance and implementation as an accurate tool.