Effects of Fly Ash on Compressive Strength and Durability Properties of Lean Concrete

Concrete production and waste generation are among human activities that negatively impact the environment. This study investigated the effects of fly ash on compressive strength and durability properties of lean concrete using appropriate standard methods. The results showed that the compressive strength of the control mix is higher than those of fly ash concrete mixes. The compressive strength of the fly ash blended mixes decreased as the replacement level increased. However, the strength increased with hydration time, and the optimal replacement level being 5%. While the chloride ion penetration and water absorption rate decreased, the sulfate resistance increased with hydration time and replacement level. The fly ash mixes exhibited better durability properties than the control mix in all durability tests conducted. The SEM-EDX analysis showed that mixes with well-packed microstructures exhibited favorable compressive and durability properties. In conclusion, Class C fly ash is recommended for lean concrete mixes at a replacement level of up to 15% when compressive strength is the primary concern, while mixes with a replacement level of 25% or more are recommended in areas susceptible to sulfate attack.