Concrete workability by compaction factor: given Wp and Wf are the weights of a cylinder filled with partially compacted and fully compacted concrete respectively, if the measured compaction factor is 0.95, how would you classify the concrete's workability?

Introduction / Context:
Compaction factor is a laboratory measure of concrete workability, especially useful for low to medium workability mixes where slump is less sensitive. It compares the density achieved under self-weight with that under full compaction.

Given Data / Assumptions:

• Compaction factor CF = Wp / Wf = 0.95.
• Standard apparatus and procedure as per test method.
• Typical classification ranges for workability.

Concept / Approach:
Compaction factor values close to 1.0 indicate that the concrete nearly achieves full compaction under its own weight—i.e., high workability. Typical guides: CF ≈ 0.7 (very low), ≈ 0.8–0.85 (low), ≈ 0.9–0.92 (medium), and ≈ 0.95 and above (high), subject to mix specifics.

Step-by-Step Solution:
Compute/interpret CF = 0.95.Map CF to qualitative bands: 0.95 → high workability.

Verification / Alternative check:
Cross-check with slump expectations; high CF usually corresponds to moderate–high slump if the aggregate grading is favorable and no segregation occurs.

Why Other Options Are Wrong:

• Extremely/very low/low correspond to CF ≤ ~0.85–0.88, far below 0.95.
• “None of these” is incorrect because the standard classification is “high.”

Common Pitfalls:

• Assuming CF of 1.0 is achievable in practice; minor differences always exist between self-weight and fully compacted conditions.

Final Answer:
high