Aggregate shape effects: for a fixed water content, workability of concrete will decrease if the aggregates contain an excess of which particle types?

Introduction / Context:
Aggregate shape and texture strongly affect workability, water demand, and packing. Mix designs control the percentage of flaky and elongated particles for this reason. This question examines which shapes reduce workability when water content is held constant.

Given Data / Assumptions:

• Water content is fixed; no admixture change.
• Aggregates may include flat, elongated, or flaky shapes.
• Workability is assessed via handling/compaction ease.

Concept / Approach:
Flat, elongated, flaky, and thin particles have higher surface area-to-volume ratios and interlock easily, leading to higher internal friction and higher water demand. At the same water content, these shapes decrease workability compared to rounded, cubical particles.

Step-by-Step Solution:
Hold water content constant.Introduce particle shapes with high aspect ratios → increased friction.Observe decreased slump/workability.Therefore, all listed shapes reduce workability; choose “All of the above.”

Verification / Alternative check:
Standards limit the percentage of combined flaky and elongated particles to maintain workable, pumpable mixes.

Why Other Options Are Wrong:
Each individual type indeed reduces workability; selecting just one omits the rest. “None” contradicts field experience and code limits.

Common Pitfalls:
Ignoring particle shape during sourcing; assuming grading alone governs workability regardless of shape.

Final Answer:
All of the above