Cracked concrete is a problem due to several factors such as poor maintenance, insufficient reinforcement, or steel corrosion leading to crack propagation. There is a need to increase the load-bearing capacity of concrete slabs and increase their life span. The use of waste polyethylene terephthalate fibres in concrete can dramatically alleviate the problem of crack propagation and failure sustainably. Furthermore, the utilization of waste plastic in this manner is environmentally friendly. This study presents the experimental investigation into the mechanical strength properties of concrete with respect to the effect of various mass fractions of polyethylene terephthalate fibre. The polyethylene terephthalate fibres were added at mass fraction of 0.5%, 1.0%, 1.5%, and 2.0%. An experimental investigation was carried out to explore the effect of varying fibre mass fractions on the slump value, rebound number, split tensile strength, flexural strength, and compressive strength. An increase in flexural strength, rebound number and compressive strength was noted with an increase in fibre mass fraction. However, a decrease in split tensile strength was noted. The addition of 0.5% fibre gave the highest compressive and flexural strength of 29.32 N/mm2 and 28 N/mm2, respectively. However, the addition of fibre lowered the split tensile strength beyond the control specimen at all fibre mass fractions. The experimental results of this study indicate that the addition of polyethylene terephthalate fibre enhances the mechanical strength of concrete at low fibre mass fraction percentages. The PET fibre reinforced concrete is suitable for use in paving and ceiling slabs at a fibre addition of 0.5% for optimum workability and mechanical strength.

Cracked concrete is a problem due to several factors such as poor maintenance, insufficient reinforcement or steel corrosion leading to crack propagation. There is a need to increase the load-bearing capacity of concrete and increase its life span. The use of waste polyethylene terephthalate fibres and fly ash in a hybrid concrete composite dramatically alleviates the problem of crack propagation and failure sustainably. This study aimed to optimize a waste polyethylene terephthalate fibre/fly ash hybrid cement composite. The concrete test specimens were fabricated using polyethylene terephthalate fibres and fly ash following a full factorial experimental design. The developed specimens were then tested to ascertain their workability and material strength properties. The combined effect of fibre addition and fly ash showed a general decreasing slump value for all quantities of fly ash content. The combined optimum compressive strength for fibre and fly ash was at 0.5 % and 15 %, respectively, with a strength of 15.54 N/mm2. The optimum split tensile strength of 2.79 N/mm2 was realised at 0.5 % fibre and 20 % fly ash mass fractions. The optimum flexural strength for fibre and fly ash mass fractions was obtained at 0.5 % and 30 %, respectively. The trend observed by the rebound number followed that of the compressive strength. However, the non-destructive rebound hammer method gave significantly lower strength values than the destructive test method.

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