Bulk density (unit weight) of aggregates: identify the factor that bulk density does not depend upon during standard measurement procedures.

Introduction / Context:
Bulk density (unit weight) of aggregates is the mass of aggregate required to fill a container of a specified volume under standard conditions, including the voids between particles. Understanding factors affecting bulk density is essential for batching concrete by volume and for estimating yield and storage needs.

Given Data / Assumptions:

• Standardized containers and rodding/tamping procedures are used.
• Aggregate moisture and surface condition are controlled.
• Focus is on inherent aggregate properties versus measurement artifacts.

Concept / Approach:
Bulk density depends on particle size and shape (which affect packing), grading (distribution across sizes), and specific gravity (mass per particle volume). However, when standardized containers and procedures are used, the size and shape of the container are not variables; they are fixed by the method and so should not influence the result if used correctly.

Step-by-Step Solution:
Recognize dependencies: better grading → denser packing → higher bulk density.Angular/flat particles pack less efficiently than rounded particles.Higher specific gravity increases mass per given bulk volume.The container is standardized; therefore bulk density does not depend on container size/shape.

Verification / Alternative check:
Standards prescribe calibrated measures (e.g., 3 L, 15 L) and rodding counts. When procedures are followed, container geometry does not vary across tests, hence not a dependency.

Why Other Options Are Wrong:

• Size/shape of aggregates: directly influence packing.
• Specific gravity: higher particle density increases bulk mass.
• Grading: affects void content and compaction.
• None of these: incorrect since there is a valid factor that does not affect the result.

Common Pitfalls:
Using non-standard containers or techniques introduces variability; the test must be standardized to isolate material properties.

Final Answer:
Size and shape of the container