EFFECT OF VARYING FIBRE LENGTH ON THE PROPERTIES OF RECYCLED TYRE STEEL FIBRE CONCRETE

Purpose: Tyre waste is a global environmental challenge, with millions of tyres discarded annually. Efforts towards recycling waste tyres involve their breakdown to component materials for use in various aspects of industry. Recycled tyre steel bead wires are one of such components. This study assesses the effect of varying recycled tyre steel fibre (RTSF) lengths on workability, compressive strength and tensile strength of RTSF concrete.

Design/methodology/approach: An experimental research design was adopted. RTSF length was the independent variable and the dependent variables comprised workability, measured using the slump test (mm), compressive strength and tensile splitting strength, measured on 50 x 50 mm cube and 150 x 300 mm cylinder specimens on the 28^th day. Control variables were concrete mix proportion, a constant fibre diameter (1 mm) and volume fraction (1%), other fibre characteristics, curing conditions and testing procedures.

Findings: The findings showed that the inclusion of RTSF reduced concrete slump to 0 mm in mixes with long fibres. Incorporation of RTSF to concrete increased compressive strength by 15% and tensile splitting strength up by 25% for the longest fibres. Concrete with mixed fibre lengths gave strength values comparable to RTSF concrete specimens with fibres of length equal to the average length of the mixed fibre specimens. Crack coalescence contributions of RTSF were also observed.

Research limitations/Implications: Findings from the study are limited to the use of steel bead wires from “Mecho 4.00 – 8 58J” tricycle tyres, physically assessed to be in good condition and a fibre volume fraction of 1%. The study showed that, concrete performance can be improved through adequate management of the length of RTSF incorporated into concrete mixes.

Practical implications: The study recommended that RTSF length should be considered as an important independent variable in the design of RTSF concrete.

Originality/value – The study revealed the impact of RTSF length on workability, compressive and tensile splitting strength of concrete. The findings will provide a basis for optimisation of properties of RTSF concrete.