Measuring workability of low w/c concrete — suitable field test For concrete mixes with a low water–cement ratio (stiff mixes) where slump may be near zero, which test is more appropriate to assess workability?

Introduction / Context:
Workability tests must match the consistency range of the concrete. Slump is insensitive for very stiff mixes because even workable low w/c concretes can show little to no slump, giving misleading results.

Given Data / Assumptions:

• Mixes have low water–cement ratios (stiff, harsh consistency) but are still compactable with vibration.
• Field-friendly testing is desired.

Concept / Approach:
The compaction factor test measures the degree of compaction achieved under standard conditions and is more sensitive in the low-workability range. The slump test is better for medium consistencies. Tensile or flexural strength tests are hardened concrete tests and do not measure fresh workability.

Step-by-Step Solution:

Verification / Alternative check:
Standards and textbooks recommend compaction factor or Vebe time tests for stiff concretes.

Why Other Options Are Wrong:

• Slump: insensitive at low slump values for stiff mixes.
• Tensile/Flexural: hardened concrete properties, not workability tests.

Common Pitfalls:
Relying on slump alone across all consistencies; not considering vibration effort available at site.

Final Answer:
Compaction factor test