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Contribution to study the influence of steel fiber on the high strength concrete

مساهمة في دراسة تأثير الألياف الفولاذية على سلوك البيتون عالي المقاومة

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 Publication date 2016
and research's language is العربية
 Created by Shamra Editor




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This research presents an experimental study about the effect of steel fibers on the main variables of stress- strain curve for high strength concrete on simple compression, which are: shape of stress- strain curve, ductility factor, energy absorption capacity. For this purpose, series of cylinders concrete specimens were prepared in compressive strength (70 MPa). the steel fiber with aspect ratio of L/D =70 were added at the volume fractions of (0-1-1.5-2)%. The cylinders were tested under a monotonic loading at compression, and as a result of the tests, the total curve of stress- strain was obtained. The experimental results of research showed a positive effect of steel fibers on the behavior of high strength concrete, this effect increased with increasing volume fraction of steel fibers. It can be seen from stress-strain curve, whereas the slope of the ascending branch is not much affected. The descending branch of the stress- strain curve decreases by the increase in the fiber volume fraction. This means the ductility and toughness improve with the addition of steel fibers and as a result the behavior of high strength concrete has gone far away from being brittle as it is used to be.

References used
FORSTER,S.W. High-Performance Concrete-Stretching the Paradigm. Concrete International, V. 16, No. 10, 1994, pp. 33-34
BREITENBŰCHER, I. R. Development and applications of high-performance concrete, Materials and Structures, V. 31, April 1998, pp. 209-215
RUSSEL, H. G. ACI Defines High-Performance concrete. Concrete International, V.21, No. 2, 1999, pp. 56-57
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This research presents an experimental study behaviour of high strength concrete, for evaluation of stress - strain curve and derivation of factors of equivalent compressive stress block, we depend it in design of high strength concrete elements. For this purpose, number of cylinders specimens with strength 60 MPa were prepared and tested in compression, then curve was obtained. The results showed the possibility of producing high strength concrete from local materials and with strengths are highest than those were obtained, the resulting diagrams of curve are shown to be essentially linearly elastic up to failure with a steeper declining portion of the stress - strain diagram, which agree with the results of global researches, the failure was almost sudden and rapid with increasing strength which shows that the highstrength concrete less ductile than normal concrete at the failure. Curve of high strength concrete differs from that normal concrete, this affects on the properties of rectangular equivalent stress block which requires modifications on the factors led to optimum represent for it and with evaluation of curve of the tested specimens, the diagram takes a trapezoidal shape ( ), its value at the top is and the depth of the compressive block is and we found and ( is average compression/cylinder compressive strength of concrete, is ratio of the active depth that defined location of compression force center), when concrete strength increases up , the diagram shape will be closer to triangular than trapezoidal and then curve takes the shape of triangle its value at the top is and the depth is and with replacing triangular diagram to rectangle.
Recently worldwide researches have been devoted to the use of steel fibers recovered from used tires in concrete. In Syria the amount of recovered steel from used tires is estimated about 6000 tons/year. For this purpose a bead wire having a diamete r of 0.8 mm from burnt tires was extracted and used. Three mixes with cement content 300- 350 -400kg/m3 were produced incorporating three different volumes of fiber 0.5%, 1.0%, and 1.5% and three different length 30-40-60 mm. The concrete obtained by adding these fibers evidenced a satisfactory improvement of the fragile matrix mostly in terms of toughness and post cracking behavior On the other hand it was improvements in compressive strength by steel fiber inclusion the interesting results confirm the promising application of concrete reinforced with steel fibers extracted from used tires in aircraft pavement hydraulic structures and ground slab in fabrics.
Recently, the importance of high Strength concrete has appeared due to its application in manufacturing most of the concrete structures and members, as well as to its importance in the implementation of civilian facilities like bridge bases, skyscr apers and in implementing the columns and platforms which carry oil installations carried out in the oceans and seas. The research aims to design concrete mixtures with cylindrical resistors ( 55- 65- 75 Mpa) according to the American code AcI-211-4R-93 by using local and appropriate additions as well as explaining the method used in designing. Then, studying the transformation in stress strain curve – deformation (σ- ζ ) undergoing a simple pressure on the previous samples throughout the available devices. Then, it was compared to the charts obtained mathematically .Law behaviour of stress strain and deformation curve was rated, in addition to modulus of elasticity taken from the chart. Couple of results and recommendations related to the issue were concluded, those which were applied in praxis.
This research presents an empirical study about the behavior of High Strength Concrete beams under the static cyclic loading. It determines the influence of cyclic loading on the moment capacity and deflection of HSC beams. A comparison of the mome nt capacity and deflection in both kinds of loading (monotonic and cyclic loading) were achieved. High Strength Concrete mixture was designed, based on the specifications of the American code ACI 211.4R-93. Thirty six concrete beams were prepared, nine of them were tested under monotonic loading and the rest of beams were tested under cyclic loading. The cyclic loading was performed for (5,10,15) cycles, at a range from zero to 65%, 75%, 85% of the minimum expected monotonic load. The results showed that the cyclic loading have positive effect on the flexural behavior of HSC members, whereas the moment capacity increased and the deflection decreased, especially at a range from zero to 75% of the minimum expected monotonic load, when the number of cycles was 5,10,15.
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