Study on Mechanical and Microstructural Properties of Concrete with Fly Ash Cenosphere as Fine Aggregate—A Sustainable Approach

The utilization of waste materials in concrete lowers its cost, and this method of dealing with the problem of trash disposal is viewed as the most environmentally friendly. Fly Ash Cenospheres (FAC) are one of the principal wastes produced by coal power stations. The huge volume of FAC produced worldwide has created a sustainability challenge, owing to the potential implications of inappropriate disposal. Using cenospheres in concrete materials would make effective and efficient use of these waste products while also supplementing what the present raw material, such as river sand, can supply for concrete material production. Though the application of FAC in concrete is currently carried out by the construction industry, there is still a lack of understanding about its performance in concrete with Manufactured Sand (M Sand) as fine aggregate. Therefore, in this paper, a comprehensive study explores the concept of adding FAC to M Sand concrete. The properties of fresh and hardened concrete, such as density, workability, compression, split tensile, flexure, and impact resistance after the addition of FAC in volume replacement (0–100% with a difference of 5% at thirteen different ratios) is represented, followed by microstructural analysis. From the results, it can be concluded that strength reduction takes place as FAC content increases from 0–100%, however, the strength is within the target limit of 31.2 N/mm2 of conventional concrete (CC) of grade M25 when the percentage replacement is below 35% of volume. Therefore, reducing the volume of fine aggregate does not negatively affect the strength properties, but also impacts the environmental concern positively with optimum recommendation of 35% of fine aggregate as FAC.