Steel Fiber Reinforced Concrete Made With Fibers Extracted from Used Tyres
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Date
2009-11
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Addis Ababa University
Abstract
Concrete is considered a brittle material, primarily because of its low tensile strength and low
tensile strain capacity. The low tensile strength of concrete is due to internal flaws and microcracks
present in the concrete. The use of randomly distributed, discrete fibers to improve the
mechanical properties of the matrix is an age-old and intuitive concept. Recently, worldwide
researches have been devoted to the use of steel fibers recovered from used tyres in concrete.
The concrete obtained by adding these fibers evidenced a satisfactory improvement of the fragile
matrix, mostly in terms of toughness and post cracking behavior. As a consequence steel fibers
extracted from used tyres appear to be a potential candidate for steel fiber reinforced concrete.
To this effect this research work was undertaken aiming to investigate the mechanical behavior
of concrete reinforced with steel fibers recovered from used tyres and to quantify the benefits
obtained by the concept of SFRC over conventional concrete. For this purpose a bead wire
having a diameter of 0.89 mm extracted from burnt used tyres was used and three grades of
SFRC namely C-25, C-40 and C-60 were produced incorporating three different volumes of fiber
i.e. 0.5%, 1.0%, and 1.5%. Furthermore each volume fraction enclosed three different fiber
lengths namely 20mm, 40mm and 60mm. For comparison purposes, plain control samples were
also considered. The test program included slump test, compressive strength test, impact
resistance test, flexural tensile strength and toughness tests including load-deflection curve,
determination of first-crack point, and toughness index.
Workability of fresh concrete was largely influenced by the presence of steel fiber; on the other
hand it was unlikely to achieve considerable improvements in compressive strength by steel fiber
inclusion. Due to the addition of fibers, the flexural tensile strength and the post-crack energy
absorption capacity were greatly increased. As far as impact test is concerned both the first crack
and ultimate failure strength were enormously improved. The interesting results confirm the
promising application of concrete reinforced with steel fibers extracted from used tyres.
However, further, research work is still necessary in order to have a more in-depth understanding
of the material properties and to evaluate possible practical applications.
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Keywords
Concrete is considered