EFFECT OF RECYCLED TYRE STEEL FIBRES ON STRUCTURAL PERFORMANCE AND IMPACT RESISTANCE OF RUBBERIZED CONCRETE

Abstract

The disposal of waste tyres continues to raise an environmental concern on the world. The dumping of used tyres is a serious environmental problem mostly in urban areas of Kenya and other urbanized areas of African countries. Many researches have been done on the use of waste tyre rubbers in concrete, but most of the tyre rubbers are only being used for production of non-structural Concrete, as filling materials, which in turn reduce its potential use in Civil Engineering Construction industry. The major cause, is the reduction in mechanical strengths of rubber concrete which makes it unsuitable for structural component subjected to heavy static or dynamic forces. In this research, Recycled tyre steel fibres(RTSF) were used to investigate their effect on structural performance of rubber concrete. Crumb Rubber ranging of (0.15mm-2.36mm) was used for partial replacement of natural fine aggregates by 5,10,12.5,15 and 20% volume to evaluate the effect of Crumb Rubber volume on concrete mechanical properties. For investigating the effect of the recycled tyre steel fibres on rubber concrete, a resulted optimum value of 12.5% Crumb Rubber volume was mixed with different percentages of RTSF by 0.3,0.6, 0.9 and 1.2% of mass of the concrete with the fibres having different lengths which are 60,40 and 20mm. Three different mix groups: (CR0, CR5, CR10, CR12.5, CR15, CR20); (CR12.5-V0.3L60, CR12.5-V0.6L60, CR12.5-V0.9L60, CR12.5-V1.2L60); and (R12.5-V1.2L60, CR12.5-V1.2L40, CR12.5-V1.2L20) were casted and tested at 7 and 28 days of curing. The first group were tested to assess the effect of Crumb Rubber volume on compressive and tensile strength of concrete. The second group were tested to evaluate the effect of RTSF content on properties of Rubberized concrete. The third group were casted and tested to investigate the effect of the RTSF aspect ratio on properties of rubberized concrete. The results showed that, at 12.5% of rubber content, Compressive, tensile and flexural strength reduced by 21.51, 17.44 and 17.4% respectively at 28 days; and Flexural toughness and Impact strength increased by 5.9 and 58.82% respectively at 28 days. The addition of RTSF volume up 1.2%, the compressive, tensile and flexural strength of Recycled tyre steel fibre reinforced rubber concrete(RTSFRC) reduced by 10.38, 0.27 and 4.3% respectively at 28 days; and flexural toughness and Impact strength increased by 258.75% and 741.18% respectively compared to plain concrete at 28 days. The results further indicated that, the increase in aspect ratio of RTSF resulted in increase of mechanical properties, toughness and impact resistance, but limitation should be put to avoid balling effect of RTSF caused by higher value of aspect ratio, in this regard 60mm fibre length was adopted as the maximum. The interesting results confirm the promising application of recycled tyre steel fibres and crumb rubber in construction industry.