# Practice Question: Volume of Water for Concrete Mixture

NCEES Civil PE Specification VII.C.: Concrete

**Problem**

Given a required water-cement ratio of 0.5, you are preparing a concrete mix to place the 1-foot-thick square spread footing pictured below.

If 5 sacks of cement are used in the mixture, what volume of water is required? Assume each bag of cement weighs 94 pounds.

Assume a specific weight of water of 62.4 pounds per cubic foot.

CORRECT 😃

INCORRECT 😟

**% Students Correctly Answered:**

**71.6%**

Solution

**Answer: C) 3.8 cubic feet**

Volume of Footing:

$$ V_{footing}=1\ ft\ast4\ ft\ast4\ ft=16\ ft^3 $$

Weight of Cement:

$$ W_{cement}=5\ast94\ lb=470\ lb $$

Water-Cement Ratio:

$$ w_{cr}=0.5 $$

Weight of Water required:

$$ w_{cr}=\frac{W_{water}}{W_{cement}} $$

$$ W_{water}=0.5\ast470\ lb=235\ lb $$

Volume of Water Required:

$$ V_{water}=\frac{W_{water}}{\gamma_{water}}=3.8\ ft^3 $$