Compaction Factor Test | Workability Of Concrete

Introduction

Workability of concrete is an important factor during concrete construction, workability of concrete (Factor affecting on concrete) includes the ease with which concrete can be managed | placed and compacted. Compaction factor testing stands as an important method to measure this important characteristic or factor. The Compaction Factor Test is an essential method to measure this workability by evaluating the internal energy needed to thoroughly compact the concrete. This test yields a compaction factor a numerical representation of workability – aiding in proper concrete mix design and application

In our quest to understand concrete practicality – we initially explored the slump test, a fundamental approach to aid visual assessment. This test provides valuable insight into concrete behaviour by measuring the “slump” or degradation in a concrete specimen – a fundamental step in understanding its workability. You can Read Complete The complete Article for Your better understand a concept,

Taking our understanding one step further the compaction factor test is in the picture the test is primarily designed for use in the laboratory but can also be used in the field. It is more precise and sensitive than the slump test this particularly useful for concrete mixes with very low workability. It is normally used when concrete is to be compacted by vibration, such as dry concrete, which is insensitive to the slump test

It considers the energy required for effective compaction, resulting in a numerical compaction factor. A higher compaction factor indicates greater workability, allowing tailored concrete mixing, ensuring optimal performance based on specific project requirements.

For a deep understanding of these tests to effectively navigate the world of solid functionality. Learn how to leverage this knowledge to improve your concrete mix designs and upgrade your construction projects. This article helps equip you with insights that can change your approach, making a significant impact in the competitive construction landscape. Explore further to uncover the potential of concrete functionality and enhance your manufacturing efforts.

Decoding the Compaction Factor

The compaction factor, a crucial indicator, quantifies workability. A higher compaction factor, like 0.95, signifies flowing concrete with high workability, ideal for various applications. On the other hand, a factor of 0.92 indicates medium workability, suitable for plastic concrete. Stiff plastic concrete, challenging to work with, has a lower compaction factor.

Advantages Over Slump Test

Compared to the conventional slump test, the Compaction Factor Test offers superior precision and sensitivity / making it a preferred choice, especially for concrete mixes with low workability. It becomes invaluable when compacting by vibration, a technique vital for dry concrete, which often does not respond well to the slump test.

The Working Principle of compaction factor test.

This test centres on determining the degree of compaction achieved by allowing a specific volume of concrete to fall through a standard height. The resulting compaction factor is determined by the density ratio, comparing the achieved density to that of fully compacted concrete.

Apparatus

Compaction factor apparatus

Trowels

Hand scoop

Balance

Conducting the Test

Procedure For Compaction factor Test

Preparation of Concrete Sample:

Take a representative sample of fresh concrete and ensure it is properly mixed.

Placing Concrete in Upper Hopper:

Place the concrete sample in the upper hopper up to the brim.

Opening the Trap-Door:

Open the trap-door of the lower hopper, allowing the concrete to fall freely onto the cylinder below.

Adjustments for Dry Mix (if applicable):

If the mix is dry and does not fall freely, use a rod to assist in placing the concrete and ensuring it reaches the cylinder.

Trimming Excess Concrete:

Cut off any excess concrete above the top level of the cylinder using a plane supplied with the apparatus.

Cleaning and Filling to the Top Level:

Wipe the outside of the cylinder clean.

Fill the concrete exactly to the top level of the cylinder.

Weighing the Partially Compacted Concrete:

Weigh the cylinder with the concrete to the nearest 10 grams. Record this weight as the known weight of partially compacted concrete.

Evacuating and Filling for Full Compaction:

Empty the cylinder and refill it with concrete from the same sample in layers approximately 5 cm deep.

Achieving Complete Compaction:

Heavily ram or vibrate the layers to ensure complete compaction of the concrete.

Weighing the Fully Compacted Concrete:

Weigh the cylinder with the fully compacted concrete to the nearest 10 grams. Record this weight as the weight of fully compacted concrete.

Calculating the Compaction Factor:

Calculate the compaction factor using the ratio of the weight of fully compacted concrete to the weight of partially compacted concrete.

Compaction Factor = Weight of partially compacted concrete/Weight of fully compacted concrete

Compaction Factor	Workability Level
Above 0.92	High Workability
0.88 – 0.92	Medium to High Workability
0.80 – 0.88	Medium Workability
Below 0.80	Low Workability

Calculation for Compaction Factor

Example :- calculate the compaction factor for a hypothetical concrete mix with a maximum aggregate size of 20mm. We’ll use a simplified example where the weight of fully compacted concrete is 2400 grams and the weight of partially compacted concrete is 2200 grams.

Calculation :-

Weight of Fully Compacted Concrete (W_fully_compacted): 2500 grams

Weight of Partially Compacted Concrete (W1_partially_compacted): 2000 grams

The compaction factor (CF) is calculated using the formula:

Compaction Factor = Weight of partially compacted concrete/Weight of fully compacted concrete

Substitute the values

=2500/2200 = 1.13633 CF≈1.363

In this example, the compaction factor for the concrete mix with a maximum aggregate size of 20mm is approximately 1.36363

For workability level determination based on the compaction factor, you would refer to the workability level ranges previously mentioned in the workability table. In this case, a compaction factor of 1.36363 would fall within the High Workability range for concrete.