When would a civil engineer really use the advanced mathematical fractions and ratios?
When mixing a lasting combination of concrete for the Panama Canal locks.
Consider the job of the Panama Canal - moving maximum capacity cargo ships across a continent, including over a mountain range, to and from the Pacific and Atlantic Oceans. The canal's concrete structure must be built to withstand the erosive powers of the salt water in which it stands.
To accomplish such a task, engineers must ensure that the mix of concrete used is the best possible for dealing with salt water's degrading effects. A variety of ratios are used to help engineers solve this problem. One such ratio is a water-cement ratio that takes into account the amount of the concrete structure that will be exposed to ocean water. Another set of ratios assist in determining the amounts of various materials that will make the best mix of concrete in order to endure the ocean's pressure and chemical effects over the longest possible period of time. In addition, engineers use ratios to consider the needed amount of "concrete cover" to protect the steel reinforcements of the structure. When these materials, such as rebar, become eroded, the strength of the structure will certainly be compromised. These are just a few examples of the advanced mathematical fractions and ratios engineers use in building mega structures like the Panama Canal.
Suprenant, B.A. 2001. Designing concrete for exposure to seawater. Concrete Construction.