Introduction:
Fly ash is a byproduct of coal combustion in power plants and is commonly used as a supplementary cementitious material in concrete production. It has several benefits that enhance the properties of concrete. However, it does not directly contribute to the early age strength gain of concrete.

Permeability:
- Fly ash reduces the permeability of concrete, making it less susceptible to water and chemical penetration.
- The fine particles of fly ash fill the voids in the concrete matrix, reducing the interconnected porosity.
- This improves the durability of concrete by protecting it from moisture-related damage and chemical attacks.

Workability:
- Fly ash improves the workability of concrete by acting as a lubricant.
- It reduces the water demand of concrete mixtures, allowing for a lower water-cement ratio.
- This results in improved flowability and ease of placement, making it easier to handle and compact the concrete.

Long term strength:
- Fly ash contributes to the long term strength development of concrete.
- It reacts with the calcium hydroxide produced during cement hydration to form additional cementitious compounds.
- These compounds contribute to the strength gain of concrete over time, resulting in improved long term performance.

Early age strength gain:
- While fly ash does contribute to the overall strength of concrete, it does not significantly enhance the early age strength gain.
- The pozzolanic reaction between fly ash and calcium hydroxide is a slow process, and the strength gain is more pronounced in the later stages of concrete curing.
- Other cementitious materials such as Portland cement or supplementary cementitious materials like slag cement are more effective in providing early age strength gain.

Conclusion:
In summary, fly ash is added to concrete to improve properties such as permeability, workability, and long term strength. It reduces permeability, improves workability, and contributes to long term strength development. However, it does not directly enhance the early age strength gain of concrete.