Water–cement ratio and concrete strength: identify the incorrect statement (choose one) about how changing w/c affects strength.

Introduction / Context:
The water–cement (w/c) ratio is the single most influential parameter governing the strength and durability of fully compacted, properly cured concrete. Understanding its effect helps in mix design and quality control.

Given Data / Assumptions:

• Statements concern qualitative effect of changing w/c on strength.
• Normal, well-graded mixes with proper compaction and curing.
• No admixtures or special concretes unless implied.

Concept / Approach:
According to classic relationships (e.g., Abram’s law), for a given cement and conditions, concrete strength decreases as w/c increases because higher water content leaves more capillary voids after hydration. Conversely, reducing w/c (with adequate compaction and workability provision) raises strength up to practical limits.

Step-by-Step Reasoning:

Verification / Alternative check:
Empirical strength–w/c curves show monotonic strength reduction with increasing w/c for properly compacted mixes. Practical mix design also recognizes workability limits at very low w/c.

Why Other Options Are Wrong:
Since (a)–(d) are all correct qualitative statements, none are incorrect; therefore “None of these” is the only option that matches the prompt to “pick the incorrect statement.”

Common Pitfalls:
Assuming strength always increases simply by adding more water; neglecting the role of compaction and curing; forgetting that too-low w/c without admixtures can reduce achieved strength due to poor compaction.

Final Answer:
None of these.