Strength of Concrete MCQ with answer and solution

Concept

Workability is the ease with which fresh concrete can be mixed, placed, compacted, and finished without segregation. Common tests for workability include the Slump test, Compacting Factor test, Vebe consistometer test, and Flow table test.

Step-by-step solution

1. Identify the properties measured by each test option. 2. Slump test: Measures consistency and workability of concrete. 3. Setting time test: Measures the initial and final setting times of cement paste/mortar, not concrete workability. 4. Vebe test: Measures workability of dry or stiff concrete. 5. Flow table test: Measures workability of high-workability or self-compacting concrete. 6. Conclude that the setting time test is for cement properties, not concrete workability.

Explanation

The setting time test (measured using Vicat apparatus) determines the time taken for cement paste to set and is related to the chemical process of hydration, not the workability of fresh concrete. Slump test, Vebe test, and flow table test are standard methods used to measure the workability or consistency of fresh concrete.

Why the other options are wrong

A: Slump test is a standard workability test for medium to high workability concrete. C: Vebe test is used for low workability (stiff) concrete. D: Flow table test is used for very high workability concrete or flowable concrete.

Shortcut

Remember the primary standard workability tests: Slump, Compacting Factor, Vebe, and Flow. Setting time tests belong to cement testing.

Common mistake

Confusing cement testing methods (like setting time and soundness) with fresh concrete testing methods (like workability and air content).