Why does a concrete specification control water-cementitious material ratio rather than judging the mix only by slump?
Correct Answer
A) Water-cementitious ratio strongly affects strength and permeability after hardening
Water-cementitious ratio is a primary driver of hardened strength and permeability, while slump only describes fresh consistency. Other choices: slump is not the same as water-cementitious ratio, high water content can hurt durability, and the ratio is not merely a paperwork label.
Why This Is the Correct Answer
Water-cementitious ratio is a primary driver of hardened strength and permeability, while slump only describes fresh consistency.
Why the Other Options Are Wrong
Option B: Slump and water-cementitious ratio are always identical numbers
In concrete work, Slump and water-cementitious ratio are always identical numbers is the wrong selection for Water-cement ratio: it leaves out the controlling Water-cement ratio result: Water-cementitious ratio strongly affects strength and permeability after hardening.
Option C: A high water-cementitious ratio guarantees better freeze-thaw durability
The trap in C is A high water-cementitious ratio guarantees better freeze-thaw durability. That selection is wrong because the choice would not get the project to Water-cementitious ratio strongly affects strength and permeability after hardening, which is the Water-cement ratio result verified by the source; Water-cementitious ratio is tied to hardened concrete strength and durability.
Option D: Water-cementitious ratio is only a delivery-ticket label with no performance effect
Choice D gives Water-cementitious ratio is only a delivery-ticket label with no performance effect. Its specific error: it leaves the work at an informal or incomplete stage, while Water-cement ratio requires Water-cementitious ratio strongly affects strength and permeability after hardening.
Memory Technique
Make water-cement ratio a purpose cue; if the choice changes the purpose, it cannot be Water-cementitious ratio strongly affects strength and permeability after hardening.
Reference Hint
Open The Contractor's Guide to Quality Concrete Construction, 4th Ed., 2018; use the index entry or section for "Concrete mixture proportioning and water-cementitious ratio" to confirm that Water-cementitious ratio is a primary driver of hardened strength and permeability, while slump only describes fresh consistency.
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