Which statement best describes the effect of increasing the water-cement ratio on concrete strength and durability?

• A. Increases strength and reduces permeability.
• B. Lowers strength and durability; increases permeability and shrinkage/cracking tendency.
• C. Has no significant effect on strength.
• D. Reduces permeability and shrinkage.

Answer: (B)

Increasing the water-cement ratio changes the concrete from a dense, strong paste to a more porous one. When more water is present than what’s needed for hydration, extra capillary pores remain in the hardened paste, which lowers strength. Those same pores make it easier for fluids and aggressive ions to move through the concrete, so permeability increases and durability suffers. The wetter mix also dries out more and shrinks more, which raises the risk of cracking. So, higher water-cement ratio leads to lower strength and durability, with greater permeability and a higher tendency for shrinkage cracks. Choices suggesting higher strength or reduced permeability don’t fit because they contradict how extra water weakens the paste and creates more pathways for movement.