Procedure For Correctly Making Concrete Cube Samples For Strength Testing

In order to check concrete strength on site to ensure the batch meets the specified strength it is essential that the cubes are made to the correct standard. The cubes must be made in accordance with British Standard (BS) 1881:1983 Testing Concrete.

Equipment necessary:

Mould for making test cube



Steel float or trowel

Compacting bar

Shuttering Oil

Curing tank

Bucket to collect sample

As soon as the truck arrives on site a sample should be taken prior to any water being added to the mix. Take the sample to your designated area set aside for making the cubes. You should already have assembled the moulds so that you can immediately start to fill them while the concrete is still workable. It is also a good idea to have coated the inside of the moulds with shuttering oil to enable easy disassembly later.

Generally for each concrete sample 3 moulds should be made in order that the concrete can be tested after 7 and 28 days and the 3rd mould can be held as a spare.

Using the scoop, fill each mould up to about a third full and compact the concrete with the compacting bar with uniform strokes over the area of the mould. Generally up to 35 strokes are necessary to fully compact and ensure there are no air voids but be careful not to over compact as this may segregate the aggregate from the cement.

Next Fill the moulds up to about two thirds full and repeat the necessary compaction before filling to the top and compacting again. Once the filled cube moulds are sufficiently compacted finish the surface of the concrete with the trowel and clean the excess concrete from the mould.

Ensure the individual cubes are identifiable with appropriate labels which should at the very minimum show the date, time and cube ID number.

Once the cubes are cured they should be covered with a damp mat and stored for 16 to 24 hours in an area where the temperature is between 20 and 30 degrees celsius.

Once the necessary time has passed and the cubes have achieved the necessary strength to be de-moulded without damaging the sample, they should be de-moulded, labelled with a marker or crayon and placed in the curing tank at a temperature of 27-30 degrees celsius until they are ready to be tested

Once de-moulding is complete the moulds should be cleaned, reassembled and made ready for the next set of samples.