Which statement regarding the effect of fly ash on concrete properties is NOT correct?

Fly ash is a pozzolanic material commonly used in concrete mixtures, and it has several beneficial effects on the properties of concrete. When analyzing the statements regarding its impacts, it’s vital to understand its general influence on concrete hydration and strength development.

The assertion that fly ash leads to earlier gain in strength is not accurate. In fact, while fly ash can contribute to long-term strength gains due to its pozzolanic reactions that occur over time, it typically does not enhance early strength development. Concrete containing fly ash may initially gain strength more slowly compared to mixes without it. This is primarily due to the slower reaction of the fly ash compared to the more rapid hydration of ordinary Portland cement.

The other statements are supported by the properties of fly ash. It does improve workability, as the spherical shape of fly ash particles allows for easier mixing and placement. Additionally, fly ash can indeed increase overall strength in the long term through continued pozzolanic reactions. Furthermore, it is known to reduce shrinkage and the potential for cracking, which is advantageous for the durability and longevity of concrete structures.

Consequently, the option regarding earlier strength gain is the one that does not align with the established characteristics of fly ash when used in concrete.