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Published on 4/1/2021

Published by marketing@concretebroker.com.au

What is Blockfill concrete?

Blockfill concrete is ideal for retaining walls


Cover Photo courtesy of inchcalculator.com


What is Blockfill Concrete


Blockfill concrete is a wet concrete mix, pumped at approximately 180 slump, used to fill the besa blocks we place in retaining walls. Blockfill is a flowable mix that is utilised for the filling of cavity walls, Inspection holes, gully traps, hollow masonry blocks and difficult in-ground structures. Blockfill concrete, sometimes referred to as corefill, comprises a 10mm aggregate to assist with eliminating any pump blockages or rodding. It forms a tight pack around steel reinforcing rods, to reduse the number of voids present in drier mixes made with 20mm aggregate.

Blockfill can be either 20MPa, 25MPa, 32MPa and 40MPa. In Australia it is recommended your bloc fill concrete adheres to Australian Standard AS:1379, Specification and Supply of Concrete requirements. Concrete plants cannot fill their trucks to full capacity when delivering blockfill due to the wet mix, as larger loads can spill onto roadways and cause environmental damage and accidents.


Photo Courtesy of the sunshinecoastdaily.com.au


When ordering blockfill concrete be careful not to order large loads i.e., in excess of 4 cubic metres. Blockfill concreting can be a slower than usual process as it takes time to fill each besa block, and move from block to block without spillage. Inexperienced builders and concreters can incur large waiting time charges for the lengthy time the concrete truck spends on site. 


How much Blockfill do I need?

Blocks with 390x190mm face = 12.5 units per square metre and 2.5 units per lineal metre.
To fill 200mm bond beams allow 0.013m3 of concrete per lineal metre of beam.

To core fill 150mm ‘H’ blocks allow 0.65m3 of concrete per 100 blocks.
To core fill 200mm blocks allow 0.8m3 of concrete per 100 blocks.

To core fill 200mm ‘H’ blocks allow 0.84m3 of concrete per 100 blocks. To core fill 300mm blocks allow 1.1m3 of concrete per 100 blocks.
To core fill 300mm ‘H’ blocks allow 1.32m3 of concrete per 100 blocks.

Remember blockfill concrete is slightly more expensive than normal (N) concrete mixes. To obtain the required compressive strength at 28 days suppliers are required to add more GP Cement to the blockfill mix, due to the large amount of water in the mix (i.e., to obtain an 180 slump). In addition to this most concrete suppliers charge more for the 10mm aggregates they place in their blockfill mixes.


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Tags: besa blocks blockfill concrete concrete Melbourne concrete supply concrete Sydney corefill retaining walls

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