Performance evaluation on bond, durability, micro-structure, cost effectiveness and environmental impacts of fly ash cenosphere based structural lightweight concrete

Abstract

The production of huge fly ash waste from thermal power plants and gradual depletion of natural aggregates due to their high consumption in concrete making are two major threats to the sustainability of the environment. The strategic utilization of this waste as a replacement of natural aggregate in production of concrete can solve both the problems simultaneously. Hence, this study aims to evaluate the performance of structural lightweight concrete (LWC) containing fly ash cenosphere (FAC), a by-product of fly ash, in order to check its suitability for construction. In this study, one control concrete mix, i.e., without FAC, and other ten concrete mixes utilizing FAC as the replacement of natural fine aggregate (NFA) at the increment of 20% and with/without superplasticizer (SP) are prepared. The Mechanical properties (compressive and bond strength), durability aspects (sulphuric acid, magnesium sulphate and sodium chloride resistance) and the microstructural characteristics from X-ray diffraction and scanning electron microscope analyses of these mixes are evaluated. Moreover, the environmental impact assessment and cost-effective analysis are also conducted. From this investigation, it is found that the structural LWC can be produced by utilizing high volume FAC with/without SP with the acceptable mechanical and durability performances. Further, the concrete with 80% FAC and SP is found to be optimum having compressive strength of 32.59 MPa, which satisfies M25 grade concrete as per IS 456 (2000), meets ACI 213 (2014) requirements of structural LWC and has also acceptable durability properties. The microstructure studies have also supported the strength and durability results of these mixes. Moreover, these mixes are found to be cost effective and environmentally friendly. Hence, structural LWC prepared with a high volume of FAC and SP can be recommended for construction, which reduces the cost and environmental impacts significantly and preserves natural resources for the future generations.