To increase the slump by one inch, how much water should be added per cubic yard of concrete?

To increase the slump of concrete by one inch, it is generally accepted that adding 1.0 gallon of water per cubic yard of concrete will achieve this result. This relationship between water content and slump change is based on the principles of concrete engineering, where the workability and flow of concrete are affected by its water-to-cement ratio.

When more water is added, it lubricates the mix, allowing for better flow and higher slump, which indicates increased workability. While different mixes and conditions may slightly alter this requirement, 1.0 gallon is widely recognized as the standard quantity for increasing slump effectively without compromising the integrity of the mix too much.

The other options do not accurately reflect the typical requirements for increasing slump in concrete. 0.5 gallons would likely not provide enough of an increase, while 1.5 gallons might be excessive for just a one-inch increase, and 1.0 cubic feet represents a volume measurement that does not correlate directly with water addition in this context.