engleski

Mechanical properties of high strength concrete with recycled steel fibres from waste tyres

Durability of concrete is highly defined by its possibility to resists cracking. Low tensile strength and brittleness are often responsible for micro cracking of concrete surface and accordingly its lower resistance to penetrability of aggressive agents. In highly aggressive environments with presence of dynamic loadings mechanical properties together with permeability of concrete are detrimental for its durability. High strength fibre reinforced concrete can be solution in these environments because it allows control of the crack opening and assures structural continuity. Since use of industrial steel fibres in concrete mixture significantly raises the costs of concrete, nowadays the use of supplement materials is explored. Since 2006, when European Commission prohibited any kind of waste tyres disposal, waste tyres became valuable resource. During mechanical recycling of waste tyres is possible to obtain products which are all reusable in concrete industry ; rubber, steel and textile fibres. In this paper use of recycled steel fibres with and without addition of recycled rubber is explored, all in order to obtain high strength fibre reinforced concrete. Although, steel fibres obtained during mechanical recycling of waste rubber are irregular, with different lengths and diameters previous studies showed that they represent good supplement for industrial fibres. Rubber granulates used during this research have diameter from 0, 5 to 2 mm. Seven concrete mixtures was prepared during this research including different ratios of industrial and recycled steel fibres (100I0R ; 50I50R ; 0I100R) with and without addition of recycled rubber (5% by total volume of aggregate). In order to evaluate the influence of combining industrial and recycled steel fibres, with or without addition of the rubber on mechanical properties of concrete following testing was performed: compressive strength, flexural strength, modulus of elasticity, toughness, abrasion, freezing resistance and shrinkage.

fibre reinforced concrete; recycled steel fibres; waste tyres; rubber

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