TENSILE CRACK EXPOSURE TESTS.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MISS
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Eighty-two reinforced beams were made of concrete with a nominal compressive strength of 3500 psi at 28 days age. Air-entrained and nonair-entrained concrete were used. Seventy-four beams were reinforced with rail-steel bars, of which 64 had deformations conforming to ASTM Designation A 305-50T and 10 had old-style deformations. Eight beams were reinforced with billet-steel bars having deformations conforming to ASTM Designation A 305-50T. Coverage over the steel was either 34 in. or 2 in. and bars were placed in either bottom or top position when the concrete was placed. Seventy-two beams were stressed from 20,000 to 50,000 psi by third-point loading and in the loaded condition exposed to severe natural weathering at half-tide elevation on the beach at Treat Island, Cobscook Bay, Maine. Ten control specimens were exposed but not loaded. Results after three winters exposure indicated that only air-entrained concrete specimens are sufficiently durable to withstand this type of exposure. Evaluation of the test results was based on the condition of the specimens after two winters exposure because of the rapid deterioration of the nonair-entrained concrete beams which constituted the majority of the specimens in the program. The test results indicate that specimens with bars having deformations complying with ASTM Designation A 305-50T performed more satisfactorily than did those with old-style deformations. No effects of depth of protective concrete over the reinforcing steel were revealed. Author
- Structural Engineering and Building Technology