Abstract
This paper investigates the possibility of combining steel fibers with different weight percentages along with their functions in increasing compressive strength, indirect tensile strength and bending strength. In this study, two types of steel fibers, hooked and crimped, have been employed in the preparation of samples. These fibers have a length to diameter ratio of 30 mm and 50 mm (L/D=30 and L/D=50). Further, the combination of these fibers caused a reduction in concrete flow and reduced its efficiency. The combination of these fibers caused considerable increase of concrete bending strength compared to fibreless and single-fiber type concretes. In this research, tensile strength and bending strength of samples with 1.5%, 2% and 2.5% fibers were investigated in which the tensile strength and bending strength of all samples increased. However, there were very considerable increases in tensile strength and bending strength of samples made with hybrid crimped fibers. The results indicated that steel fibers did not have much impact on concrete compressive strength.
Highlights
Concrete, considering its structure, has advantages and disadvantages among which tensile strength and low bending strength versus its high compressive strength can be mentioned
Steel round bars were used to improve the brittle behavior of concrete under tensile forces
Tests indicated that steel and polypropylene fibers used in concrete improve the behavior of columns on fire
Summary
Concrete, considering its structure, has advantages and disadvantages among which tensile strength and low bending strength versus its high compressive strength can be mentioned. Rodrigues et al, studied the behavior of concrete columns reinforced with fibers on fire. To replace steel bars by steel fibers is not a good option when concrete is on fire [4].Vandewalle, did some experiments on hybrid fiber-reinforced concrete He used three types of fiber: very short fibers with a length of 6 mm, short fibers with a length of 13 mm and long hooked-end fibers with a length of 35 mm. Milind V mohod et al, in this experimental investigation for M30 grade of concrete to study the compressive strength and tensile strength of steel fibers reinforced concrete containing fibers varied by 0.25%, 0.50%, 0.75%, 1%, 1.5% and 2% by volume of cement cubes of size 150mm×150mm×150mm to check the compressive strength and beams of size 500mm×100mm×100mm for checking flexural strength were casted. Measures should be adopted for the even distribution of fibers and preventing them from being separated and intertwined into balls, so as to produce an efficient mix to cast, agglomerate and smoothen [2]
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