Effect of flaky particles in aggregates for concrete: What are the consequences of having an excess percentage of flaky particles?

Introduction / Context:
Particle shape influences packing, surface area, and interlock. Flaky particles (with small thickness relative to other dimensions) harm both fresh and hardened concrete properties when present in excess.

Given Data / Assumptions:

• Standard shape tests classify flaky or elongated particles.
• Concrete intended for structural use with vibration.

Concept / Approach:
Flaky particles tend to orient and bridge, creating voids and harsh mixes. They increase specific surface area, raising water and fines demand for a given slump. In hardened concrete, planes of weakness develop along thin particles, reducing strength and durability. Therefore, specifications usually limit flaky/elongated particles; a common rule of thumb is to keep them below about 15% by mass.

Step-by-Step Solution:
Relate shape → higher surface area and poor packing → less workable mix.More water/fines needed → increased paste content → potential shrinkage.Hardened performance suffers due to weak planes and higher porosity.Hence limits (≈ 15%) are adopted to control quality.

Verification / Alternative check:
Aggregate standards specify shape indices and maximum percentages for flaky and elongated particles.

Why Other Options Are Wrong:
Each individual consequence is real; excluding any understates the impact of flaky particles.

Common Pitfalls:
Assuming that stronger paste can offset poor aggregate shape; ignoring the increased segregation risk in pumped concrete.

Final Answer:
All of the above.