Has anyone ever calculated how much it costs for extra mixing water in terms of how much extra cement would have to be added to maintain the same strength?
The Alpha Portland Cement Company once published a calculation showing the cost of the water to be the equivalent of 17 cents per gallon based on a cement price of $1 per bag. At today's price of about $1.60 per bag the price would be 27 cents per gallon. Their calculation assumed that a mix with oneinch top size gravel at a water-cement ratio of six gallons per bag would have a slump of two inches and produce concrete of 4000 psi. If the slump were increased to nine inches, nine extra gallons of water would have been added per cubic yard. To maintain the same strength, by keeping the same water-cement ratio of six gallons per bag, would require 1 1/2 extra bags of cement.