PSI - Issue 70

J. Arun Prasad et al. / Procedia Structural Integrity 70 (2025) 690–697

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1. Introduction Fly ash is a byproduct of coal combustion in power plants and is a valuable material that can be used in construction projects. It is a fine powder that is collected from the flue gases produced during the burning of coal. Fly ash is a versatile material that can be used in a variety of construction applications, including concrete production, road construction, and soil stabilization. In concrete production, fly ash can be used as a partial replacement for cement. When mixed with water and aggregates, fly ash reacts with calcium hydroxide to form compounds that improve the strength and durability of the concrete. This can result in a more sustainable and cost-effective concrete mix that reduces the need for cement, which is a major source of carbon dioxide emissions in the construction industry. Coal is widely used to generate electricity throughout the world. About 41% of global electricity is produced in thermal power plants fueled by coal and an increase to about 44% is expected by 2030. After combustion of coal, fly ash is produced as a waste product in large quantities. It is estimated that approximately 750 million tones are produced annually worldwide. Coal is widely used to generate electricity throughout the world. About 41% of global electricity is produced in thermal power plants fueled by coal and an increase to about 44% is expected by 2030. After combustion of coal, fly ash is produced as a waste product in large quantities. It is estimated that approximately 750 million tones are produced The incorporation of industrial by-products such as Cenospheres — lightweight, hollow aluminosilicate microspheres derived from coal fly ash — has become a key strategy for enhancing sustainability and performance in cementitious composites. Arunachalam et al. (2023) demonstrated that replacing cement partially with Cenospheres and silica fume can reduce concrete density by 35% at 30% Cenosphere content without compromising mechanical strength. Their microstructural analysis revealed the presence of mullite and aluminosilicates, which compensate for reduced portlandite and contribute to long-term durability. Early work by Montgomery and Diamond (1984) showed that Cenospheres improve mechanical behavior primarily through physical mechanisms; they act as crack arrestors, enhancing energy dissipation and crack path tortuosity without significant chemical bonding to the cement matrix. Blanco et al. (2000) evaluated Cenospheres as lightweight aggregates, reporting a 20 – 30% density reduction with marginal compressive strength loss, while also noting improved thermal insulation and comparable acoustic absorption to expanded clay concrete. Kolay et al. (2000) characterized Cenospheres’ physical properties, highlighting their low specific gravity (0.67), thermal stability up to 280°C, and favorable spherical shape that enhances workability and mix stability. However, Shukla and Bose (2002) identified the high-water absorption of Cenospheres — up to 18 times that of sand — due to their porous internal structure, requiring careful adjustment of water-cement ratios to avoid hydration issues.Barbare et al. (2003) found that using Cenospheres as fine aggregate could reduce concrete density by 30% while achieving compressive strengths of 25 – 30 MPa, improving internal homogeneity. Tiwari et al. (2004) reported enhanced acoustic performance in concrete with 40% Cenosphere content, noting a 25% noise reduction despite a slight decrease in porosity. From a durability perspective, Wang et al. (2012) observed that Cenospheres mitigate alkali-silica reactions by lowering pore solution alkalinity through pozzolanic reactivity. Bajare et al. (2013) studied coal combustion bottom ash as a cement replacement , finding that a 20% substitution preserved compressive strength and reduced CO₂ emissions by 23%, although higher replacement levels reduced strength but improved durability. Overall, these studies annually worldwide. 2. Literature review