Performance evaluation of cashew nutshell ash as a binder in concrete production

The agro-industrial sector annually produces large volumes of waste by-products which as a result of the ignorance of their values as well as their ineffective management, pose environmental, societal and economic threats. Thus, this study explored the ash from cashew nutshell waste and replaced it with Portland limestone cement (PLC) at 5%, 10%, 15% and 20% using a mix design ratio of grade 25 MPa concrete (M 25). The cashew nutshell was sun-dried for 14 days and then burnt in a gas furnace at a temperature of 750 °C for 5 h to obtain cashew nutshell ash (CNSA). The chemical and physical properties of the CNSA were examined while the workability of the fresh concrete was investigated. Moreover, the mechanical and durability properties of the hardened concrete were carried out while the microstructures of the concrete samples were analyzed. The experimental findings revealed that CNSA met the requirements for use as a pozzolanic material. The slump and the compacting factor increased with increasing CNSA content. Moreover, both compressive, splitting tensile and flexural strengths of the hardened concrete increased as the content of CNSA increased but optimum at 15% replacement level. Furthermore, the CNSA concrete resisted more sulfate attack than the Portland cement concrete (control). The micromorphological analysis exhibited a reticular structure and adequate filling ability with the incorporation of CNSA content in the mix. Hence, it is recommended that CNSA can be incorporated as a construction material in the concrete production at the optimum replacement with PLC at 15% for structural application and 20% for non-load bearing application. This study is advantageous because fresh concrete would remain workable for longer periods, thus, resulting in the reduction of construction joints. Moreover, the utilization of CNSA concrete is also beneficial in an environment with high sulfate content. Finally, the developed model equations from this study can be used in the development of mix design of blended concrete as well as a better refinement of existing procedure of concrete mix design provided the chemical composition of the materials is established.