**Answer:**

The free water cement ratio is an important parameter in the design of concrete mixtures. It represents the amount of water available for the hydration reaction with cement. The ratio is typically expressed as the weight of water to the weight of cement in the mixture.

**Effect of Increasing the Grade of Concrete:**
When the grade of concrete is increased, it means that the strength requirements for the concrete have increased. This can be achieved by increasing the amount of cement or by using a higher grade of cement.

**Effect on Water Cement Ratio:**
1. **Remain Same:** If the grade of concrete is increased by increasing the amount of cement while keeping the total water content constant, then the free water cement ratio will remain the same. This is because the ratio is determined by the amount of water and cement, and if both are increased proportionally, the ratio will remain constant.

2. **Increases:** If the grade of concrete is increased by increasing the amount of water while keeping the cement content constant, then the free water cement ratio will increase. This is because the ratio is determined by the amount of water and cement, and if the water content is increased without a corresponding increase in cement, the ratio will increase.

3. **Decreases:** If the grade of concrete is increased by increasing the amount of cement while reducing the water content, then the free water cement ratio will decrease. This is because the ratio is determined by the amount of water and cement, and if the water content is reduced without a corresponding decrease in cement, the ratio will decrease.

4. **Linearly Increases:** The free water cement ratio does not linearly increase with the increase in the grade of concrete. It depends on the specific design requirements and the approach taken to achieve the desired strength.

**Conclusion:**
In summary, the effect of increasing the grade of concrete on the free water cement ratio depends on the specific design requirements and the approach taken to achieve the desired strength. It can remain the same, increase, decrease, or vary depending on the design choices made.