Fresh concrete testing: The slump test primarily measures which property of a concrete mix for site quality control and placement suitability?

Introduction / Context:
The slump test is the most widely used, quick field test for assessing fresh concrete. It ensures a mix has the right mobility for compaction and finishing without excessive segregation or bleeding.

Given Data / Assumptions:

• Standard Abrams cone, moist surfaces, proper rod tamping.
• Result interpreted immediately after lift of the cone.
• Normal (non-flowing) concrete without high viscosity modifiers.

Concept / Approach:
Slump height loss correlates with mixture consistency/workability. It does not directly measure strength; rather, it provides an index to ensure the specified workability for placement method (vibration, pumping, hand placing) and section geometry.

Step-by-Step Solution:
Perform the cone test per procedure.Measure vertical subsidence → slump value.Interpret as consistency/workability indicator.

Verification / Alternative check:
Target slump ranges are specified in mix designs based on element type and placement method.

Why Other Options Are Wrong:
Strengths (compressive/tensile) require hardened tests; impact value applies to aggregates, not fresh concrete.

Common Pitfalls:
Over-tamping, delayed measurement, or testing on an inclined surface—each distorts results.

Final Answer:
Consistency (workability).