Explanation:

The compaction factor is a measure of the workability of concrete or mortar. It is determined by the ratio of the height of the compacted concrete or mortar to the height of the concrete or mortar when it is freely placed in a test cone and compacted by rodding.

A compaction factor of 0.75 indicates very low workability. Here's why:

Workability:
Workability is a property of fresh concrete or mortar that determines its ability to be easily mixed, placed, compacted, and finished. It is an important factor to consider as it affects the ease of construction and the final quality of the hardened concrete.

Compaction Factor Test:
The compaction factor is determined using the compaction factor test, which is a standard test method to measure the workability of fresh concrete or mortar. In this test, a known quantity of concrete or mortar is placed in a standard test cone and compacted by rodding. The height of the compacted concrete or mortar is measured and compared to the height of the concrete or mortar when it is freely placed in the cone.

Interpretation of Values:
The compaction factor value ranges from 0.60 to 0.92. The lower the compaction factor, the lower the workability of the concrete or mortar. The higher the compaction factor, the higher the workability.

Compaction Factor of 0.75:
A compaction factor of 0.75 indicates very low workability. This means that the concrete or mortar is difficult to mix, place, compact, and finish. It will require a significant amount of effort to properly handle and work with this material. It may not flow easily and may require excessive vibration or compaction efforts to achieve proper consolidation.

Importance of Workability:
Workability is an important property as it affects the ease of construction and the final quality of the hardened concrete. Concrete or mortar with low workability can lead to issues such as inadequate compaction, poor consolidation, and reduced strength and durability. It can also result in increased labor and equipment requirements, leading to higher costs.

Conclusion:
In summary, a compaction factor of 0.75 indicates very low workability of concrete or mortar. This means that the material is difficult to handle and requires a significant amount of effort to properly compact and finish. It is important to consider workability when designing and specifying concrete or mortar mixtures to ensure that they can be easily placed and meet the desired performance requirements.