Abstract
The utilization of waste steel fibres (coming from the recycling process of the old tires) in production of blast resistant cement based panels was assessed. Waste fibres were incorporated in slurry infiltrated fibre concrete (SIFCON), which is a special type of ultra-highperformance fibre reinforced concrete with high fibre content. The technological feasibility (i.e. suitability of the waste fibres for SIFCON technology) was assessed using homogeneity test. Test specimens were prepared with three volume fractions (5; 7.5 and 10 % by vol.) of waste unclassified fibres. SIFCON with industrial steel fibres (10% by vol.) and ultra-highperformance fibre concrete with industrial fibres were also cast and tested for comparison purposes. Quasi-static mechanical properties were determined. Real blast tests were performed on the slab specimens (500x500x40 mm) according to the modified methodology M-T0-VTU0 10/09. Damage of the slab, the change of the ultrasound wave velocity propagation in the slab specimen before and after the blast load in certain measurement points, the weight of fragments and their damage potential were evaluated and compared. Realized tests confirmed the possibility of using the waste fibres for SIFCON technology. The obtained results indicate, that the usage of waste fibres does not significantly reduce the values of SIFCON flexural and compressive strength at quasi-static load - the values were comparable to the specimens with industrially produced fibres. With increasing fibre content, the mechanical parameters are increasing as well. Using of the waste fibres reduces fragmentation of SIFCON at blast load due to the fibre size parameters. Using of low diameter fibres means more fibres in the matrix and thus better homogeneity of the whole composite with less unreinforced areas. Regarding the blast tests, the specimen with waste steel fibres showed the best resistance and outperformed also the specimen with commercial fibres. Using of waste fibres in SIFCON technology can reduce the price of this composite by 70 % by keeping the original SIFCON extraordinary properties, which makes it very competitive material in the concrete area.
Highlights
It is estimated that over 4 billion used tires are generated every year [1]
Short fibres can bridge microcracks, which increases tensile strength, long fibres bridge macrocracks, so they can provide a stable post-peak response. As it is extremely fast phenomenon, this classical approach cannot be fully adopted, but the hybrid fibre reinforcement is still beneficial, because the same volume content of waste fibres contains more fibres than the commercial ones, so the fibres can be more homogeneously distributed within the concrete, with fewer unreinforced spaces. [15, 16] In this model, thicker and longer fibres help to keep the overall integrity of the material, whereas the shorter and thinner fibres protect the slab from the fragmentation
This paper summarizes the results of research on slurry infiltrated fibre concrete reinforced with waste steel fibres from tires
Summary
It is estimated that over 4 billion used tires are generated every year [1]. A typical tire consists of approximately 47% rubber, 22% carbon black, 17% steel cords, 5% fabrics, and the remaining percentage consists of some other minor additives [2]. Using tire waste fibres in concrete technology is limited due to the nature of the obtained fibres – in particular the high diversity of fibre geometry, contamination and bulk nature of the product. The tire fibres are made from high strength carbon steel with a tensile strength as high as 2,200 – 2,750 MPa [3], so they seem to be promising reinforcing material. The fibre volume fraction of traditional fibre reinforced concrete is limited, because excessive amount of the fibres affects the workability of the fresh concrete in a negative way. The main objective of the work presented is to provide more information about the effects of steel fibers recovered from tires on the mechanical parameters of SIFCON, with focus on its behaviour under blast loading. The modified methodology for blast resistance assessment is presented
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