How does the addition of water to fresh concrete affect the concrete strength?

• A. Decrease its strength.
• B. Increase its strength.
• C. No effect on strength.
• D. Only affects color.

Answer: (A)

Concrete strength is governed by the water-to-cement ratio. Adding water to a fresh mix raises that ratio, which leaves more capillary porosity after hydration. With more pores and less cement paste present to carry loads, the hardened matrix becomes weaker, so the compressive strength decreases. Excess water can also cause bleeding, segregation, and poor bonding, all of which further reduce strength. In short, extra water in the mix lowers the final strength, which is why the correct effect is a decrease in strength.