What is the water to cement ratio of a mix containing 725 lb of cement, 80 lb of fly ash, and 285 lb of water?

To determine the water-to-cement ratio in a concrete mix, you need to calculate the ratio of the weight of water to the total weight of the cementitious materials. In this case, the weight of the cement is 725 lb, and we should also include the weight of the fly ash, which contributes to the total cementitious content.

First, sum the weights of the cement and fly ash:

725 lb (cement) + 80 lb (fly ash) = 805 lb (total cementitious materials).

Next, the weight of water provided is 285 lb.

Now, we calculate the water-to-cementitious materials ratio:

Water-to-cement ratio = Weight of water / Total weight of cementitious materials

= 285 lb / 805 lb

= 0.353.

When rounded, this ratio can be expressed as approximately 0.35. Therefore, the correct answer reflects a calculated value just slightly over 0.35, leading to the correct conclusion that the answer aligns most closely with the option labeled as 0.39.

This ratio is crucial because it can influence the strength, durability, and workability of the concrete. For optimal performance, maintaining an appropriate water-to-cement ratio