Concrete Cube Test - Explained By Converge

May 16, 2022

Concrete cube test

The concrete cube test is used to give an idea of the compressive strength of the concrete. In this way, you can see if the creation of the concrete has been done in a good way or not. The method of this test has been used since the 19th century and is almost the same now as it was then.

 

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Compressive strength of concrete

Compressive strength in concrete is the capacity to withstand pressure on the surface without any cracks or bending. The compressive strength formula is, for concrete as for any material, is the load at the point of breaking to cross-section area on the surface face where the load was.

 

Equipment needed for a cube test of concrete

-   Cube moulds. You usually have two different sizes to choose from. One is 15 x 15 x 15 cm and the other 10 x 10 x 10 cm. They can be in either polyurethane or steel. The moulds must be crafted according to the standards in the country. For The United Kingdom, this organ is the British Standards Institute (BS EN 12390-1:2000).

 

-   Tamping rod in steel. This shall be 16 mm (approx. 0,63 in) in diameter and have a length of 60 cm (approx 24 in) with one of the ends rounded.

 

-   Trowel.

 

-   A compressive strength testing machine.

 

How a concrete cube test is done

When doing a concrete cube test, you first need to mix fresh concrete. Then, you let it cure and after that, you can test it. You should test the concrete twice, first after 7 days and then again after 14 days.

 

We will now give an overview of the process down below:

 

Preparations

-   Mix the ingredients of the concrete to the desired consistency.

 

-   Clean the cube moulds. Since you shall have at least 3 moulds and test two times, you need to clean 6 moulds.

 

-   Apply oil in the moulds after cleaning. This will make it easier when removing the mould later and not destroy the form of the concrete.

 

-   Fill the moulds with the freshly mixed concrete. This should be done in 5 cm thick layers until full.

 

-   Compact every layer with at least 35 strokes. For this, you use the rounded end of the tamping rod.

 

-   Even out the surface at the top with the trowel.

 

-   Store the samples in a place with damp air for the first 24 hours.

 

-   When 24 hours have passed, remove the moulds and let the samples cure in clean freshwater until it is time for the test.

 

The process of the cube test

-   Take out the sample and remove any water from its surface.

 

-   Place the sample on the machine in a proper way.

 

-   Apply load until failure of the cube. This will be done in different steps and not all at once.

 

-   Note the maximum load the sample can take and write down any uncommon traits that might show during the test.

 

Read more: What are concrete slabs, concrete vs cement and concrete maturity.

 

Concrete cube testing in reality

There are many things to keep in mind and you need to have a lot of knowledge to be able to execute a concrete cube test the correct way. From calculations to different standards depending on the country, this is a test that needs to be well planned and organized.

 

If you want to supervise

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Reading tip: 9 things to keep in mind when pouring concrete in cold weather.

 

Frequently asked questions

What is a concrete cube test?

A concrete cube test is when you take a sample of fresh concrete, let it cure and then test its compressive strength in a machine. By doing this, you can see if the concrete has been done properly and possibly find unwanted features of the concrete before you start to use it when building.

 

How big are the cubes in the test?

You can choose between two sizes of the cube moulds. One is 15 x 15 x 15 cm and the other one is 10 x 10 x 10 cm. What size you should choose depends on the size of the aggregates in your concrete mix.

 

What is compressive strength?

Compressive strength in concrete is the capacity to withstand load on the surface without cracking or bending.

 

Why do you test both after 7 and 14 days?

Generally, concrete has gained complete strength 28 after the pouring. After 7 days have passed, it should have gained 65% of its strength and 90% after 14 days. With this in mind, you can see if the strength develops as wanted.

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