What is the water to cementitious ratio for the same mix described above?

The water-to-cementitious materials ratio is an essential factor in determining the strength and durability of concrete. A lower water-to-cementitious ratio generally results in higher strength and lower permeability, which is desirable for most concrete applications.

In the context of the choices provided, a water-to-cementitious ratio of 0.35 represents a balance where there is sufficient moisture for hydration reactions to occur while also ensuring that the concrete achieves its desired strength. This ratio allows for optimal hydration of the cement without compromising the mixture's workability or strength.

Choosing a ratio like 0.35 is common in many concrete mixes as it often aligns with industry standards for achieving a strong and durable product. It is well acknowledged in engineering practices that this range is effective for a variety of typical concrete applications.

Other ratios, while potentially viable, may not provide the same combination of benefits in strength, workability, and durability, making 0.35 a typical choice for effective concrete performance.