How does increasing the water-cement ratio affect concrete strength and durability?

• A. Higher water-cement ratio lowers strength and increases permeability.
• B. It lowers strength and increases permeability.
• C. It increases strength.
• D. It has no effect on durability.

Answer: (A)

Water-cement ratio controls how dense the hardened cement paste becomes, which directly affects strength and durability. When more water is used, excess water leaves as the concrete cures, leaving behind capillary pores. Those pores create a weaker, more porous matrix, so the concrete’s compressive strength decreases and its permeability increases. Increased permeability means fluids and corrosive agents can penetrate more easily, reducing durability. That’s why this statement is the best: a higher water-cement ratio lowers strength and increases permeability. The idea that strength would rise with more water or that durability isn’t affected contradicts the way porosity and fluid ingress govern concrete performance.