Question

Workability of concrete mix having very low water-cement ratio has to be ascertained by

• A. Slump test
• B. Bending test
• C. Compression test
• D. Compaction factor test

Hint:

Choose the workability test based on the consistency of concrete: \[ \begin{array}{ll} \textbf{Slump Test} & \rightarrow \text{Medium to high workability} \textbf{Compaction Factor Test} & \rightarrow \text{Low workability} \textbf{Vee-Bee Test} & \rightarrow \text{Very low workability (stiff mixes)} \textbf{Flow Table Test} & \rightarrow \text{High workability} \end{array} \] Remember that the Compaction Factor Test is preferred for concrete mixes having a low water-cement ratio.

Answer 1

The Correct Option is D

Concept: Workability is the ease with which concrete can be mixed, transported, placed, compacted, and finished without segregation. Different tests are used to determine the workability of concrete depending on its consistency.
• Slump Test: Suitable for medium to high workability concrete.
• Compaction Factor Test: Suitable for low and very low workability concrete.
• Vee-Bee Consistometer Test: Suitable for very stiff concrete mixes.
• Flow Table Test: Suitable for highly workable concrete.

Step 1: Identify the type of concrete mix. The concrete mix has a very low water-cement ratio. Such concrete possesses low workability and cannot be assessed accurately using the slump test.

Step 2: Select the appropriate test. For concrete of low or very low workability, the compaction factor test provides a more reliable measure of workability because it determines the degree of compaction achieved under standard conditions. Hence, \[ \boxed{\text{Compaction Factor Test is used to determine the workability of concrete having a very low water-cement ratio}.} \] Therefore, the correct option is \[ \boxed{(D)\;\text{Compaction factor test}.} \]