Difficulty obtaining a smooth finish in concrete mix can be caused by several factors. One of the factors is hardness. Let us understand this in detail.

Hardness in Concrete Mix
When the concrete mix is too hard, it becomes difficult to obtain a smooth finish. The concrete will not be able to flow properly and settle into its final position. As a result, the surface will have an uneven finish. This can be due to several reasons such as:

- Insufficient water content in the mix
- Excessive use of cement in the mix
- Insufficient mixing of the components

These factors can result in a mix that is too hard and difficult to work with. The concrete will not have the desired consistency and will not be able to flow or settle properly.

Effects of Hardness in Concrete Mix
When the concrete mix is too hard, it can lead to several problems, such as:

- Uneven surface finish: The surface of the concrete will not be smooth and even. This can be a problem when a smooth finish is desired, such as in decorative concrete.
- Increased labor costs: When the surface finish is not smooth, additional labor may be required to fix it. This can increase the overall cost of the project.
- Reduced durability: When the mix is too hard, it can lead to cracking and other forms of damage. This can reduce the durability of the concrete, leading to additional repair costs.

Conclusion
In conclusion, hardness is one of the factors that can cause difficulty in obtaining a smooth finish in concrete mix. It is important to ensure that the mix has the right consistency and that the components are mixed thoroughly to avoid this problem. By doing so, a smooth and even finish can be achieved, reducing labor costs and improving durability.