The construction industry relies heavily on concrete as a building material. The coarse aggregate makes up a substantial portion of the volume of concrete. However, the continued exploitation of granite rock for coarse aggregate results in an increase in the future generations’ demand for natural resources. In this investigation, coconut shell was used in the place of conventional aggregate to produce coconut shell lightweight concrete. Class F fly ash was used as a partial substitute for cement to reduce the high cement content of lightweight concrete. The impact of steel fiber addition on the compressive strength and flexural features of sustainable concrete was investigated. A 10% weight replacement of class F fly ash was used in the place of cement. Steel fiber was added at 0.25, 0.5, 0.75, and 1.0% of the concrete volume. The results revealed that the addition of steel fibers enhanced the compressive strength by up to 39%. The addition of steel fiber to reinforced coconut shell concrete beams increased the ultimate moment capacity by 5–14%. Flexural toughness was increased by up to 45%. The span/deflection ratio of all fiber-reinforced coconut shell concrete beams met the IS456 and BS 8110 requirements. Branson’s and the finite element models developed in this study agreed well with the experimental results. As a result, coconut shell concrete with steel fiber could be considered as a viable and environmentally-friendly construction material.

The aim of this study is to investigate the effect of adding fly ash, an industrial by-product and coconut shell, an agricultural waste on the mechanical and flexural characteristics of eco-concrete. The study focuses on density, compressive strength, tensile strength and flexural behaviour of the coconut shell eco-concrete. Two different mixes are developed, one with coconut shell and the other with conventional aggregate and coconut shell as coarse aggregate. The cement content is replaced with class F fly ash at 0%, 10%, 20% and 30% by weight. The test result shows that the coconut shell concrete produced with 10% fly ash has recorded higher compressive, tensile strength than other proportions. Fly ash inclusion further reduces the density of coconut shell concrete. The higher deflection of coconut shell concrete before failure shows that it has failed in a ductile manner. The flexural behaviour is comparable with other lightweight concretes. It is suggested that an eco-friendly, cost effective structural lightweight concrete can be produced by using coconut shell and fly ash.