Effects of hybrid polyethylene terephthalate fibre and fly ash on mechanical properties of concrete

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 loadbearing 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 mm(-2). The optimum split tensile strength of 2.79 N mm(-2) 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.