الفهرس Only 14 pages are availabe for public view
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Abstract
Prediction of damage in plain and fiber reinforced concrete due to static load and low velocity impact is an important step in evaluating the service life of structural elements fabricated from them. An extensive study was carried out to evaluate the real role of discrete short fiber in enhancing mechanical properties and fracture toughness of conventional high strength concrete (HSC) under both static and dynamic loads. Dolomite as a coarse aggregate with 14 mm maximum aggregate size and siliceous sand were mixed together with a ratio of 3: 1. Cementitious material content of about 500 Kg/m3 ordinary Portland cement and 75 Kg/m3 silica fume was used and the water Icement ratio (w/c) was 0.35. Two different types of short fibers, namely end hocked steel and polypropylene fibers, were used with 0.5, 1.0 and 1.5% volume fraction and 5 cm length for steel fiber and 0.1, 0,3 and 0.5% and 2.5 cm length, for polypropylene. The two types of fibers were added to plain concrete mix separately and in hybrid form of 1 % steel and 0.3% polypropylene fibers, to make seven different mixes of fib er reinforced concrete (FRC). Variable dosages of superplasticizer were added to the different mixes of FRC to keep their workability at limits. Beside the traditional mechanical properties tests (i.e. compression, indirect tension and flexural) special fabricated free falling DROP weight impact machine was manufactured and used to conduct the low velocity impact tests on slab specimens, with 50x50x6 cm dimensions. The falling height of weight was 20, 40,60,80,135,180 and 270 cm. static flexural test was carried out after impact to determine the losses in the flexural behavior of FRC due to impact.