For a slump value of 150 mm to 175 mm, the compaction factor value of concrete may be about:

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OSSC JE Civil Mains Official Paper: (Held On: 16th July 2023)
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  1. 0.6 - 0.7
  2. 0.7 - 0.8
  3. 0.8 to 0.9
  4. above 0.9

Answer (Detailed Solution Below)

Option 4 : above 0.9
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Concept:

Workability of concrete:

Workability is the relative ease with which concrete can be mixed, transported, molded, and compacted. we can also say, it is the energy to overcome friction while compacting.

The workability of concrete can be measured using the following methods,

1) Slump test:

The slump test is a measure of consistency or the wetness of the concrete mix. It is suitable for field applications, suitable for concrete of high and medium workability. Slumps for various types of concrete is measured in mm.

2) Compacting factor test:

It is more accurate than a slump test. It is suitable for concrete mixes of medium and low workability. It is suitable for determining workability in the laboratory.

3) Vee-bee consistometer:

The time required for complete remoulding of concrete in seconds after placed in the mould with a slump cone. It is expressed in seconds. It is the method used to determine the workability of very dry mixes with low workability.

4) Flow table test:

Based on the percentage flow the workability of the concrete is determined. The values could range from 0 to 150 %

5) Kelly ball test:

It is a simple field testing machine that determines the depth to which a 15 cm diameter metal hemisphere weighing 13.6 kg, will sink under its own weight into the fresh concrete. Based on the depth of the penetration workability of concrete is determined

Explanation:

Consistency

Slump in mm

Compaction Factor

Vee-Bee time in seconds

Very Dry

0-25

0.7-0.8

20-10

Dry

25-50

0.8-0.85

10-5

Plastic

50-100

0.85-.9

5-2

Semi-fluid

100-175

0.9-1

2-0

We can see,

As slump increasesVee bee time decreases, as it becomes easier for concrete to flow.

Also as the slump increases, the compaction factor increases.

Hence the correct answer is option 4

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