# Forum Home Renovation Brickwork  Core-Fill Mix

## MC89

Hey guys, I have a fairly small block wall recently built. It is not retaining any land but it will be supporting one side of a deck(other side supported by posts. It's only 1m high and about 220 standard 390x190 blocks.  
I'm ready to fill the wall with grout/concrete mix and rebar but for the life of me, I can't find a recommended mix ratio.  
 I find many specifications such as must have a 200mm slump and 10mm or less aggregate and use plasticisers but that means nothing to me.   
I'm going to be doing it myself as I don't mind putting in the extra work if it saves me $500+ as I can get a good deal on landscaping supplies. A pump is too expensive and because of where the wall is located, it would take too long if I had the mix delivered.  
Would anyone be able to recommend a typical corefill ratio? 
Thanks, 
Matt

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## phild01

Sometime back I used a 2:1,river sand/ cement, wet enough for it to flow.  I didn't use any additives.  This was recommended by the suppliers of the mortar-less blocks I was using.

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## Craigoss

I had to corefill the 100 series blocks for a small garden retaining wall. All the corefill mixes tend to be proprietary blends where you can't find out what all the mix of additives are. I ended up doing a 2:1 mix and keep it runny as the holes of the 100mm series blocks are tiny.  
220 blocks will mean you will need 2m3 of fill = 20 mixer loads. Solid days work if you are working alone.

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## cyclic

> I had to corefill the 100 series blocks for a small garden retaining wall. All the corefill mixes tend to be proprietary blends where you can't find out what all the mix of additives are. I ended up doing a 2:1 mix and keep it runny as the holes of the 100mm series blocks are tiny.  
> 220 blocks will mean you will need 2m3 of fill = 20 mixer loads. Solid days work if you are working alone.

  Pretty well sums it up although 2 to 1 is probably overkill, while 4 to 1 is average for all situations so probably the perfect mix is 3 to 1, then everyone is happy.
Most landscape suppliers have 2 blends of what is called concrete blend, one being 10mm gravel, and the other being 20mm gravel. 
For block fill, I have always used 10mm.
As for additives, 40 years ago we had no additives, and the concrete was just as strong. 
When filling the blocks, use a bit of 2 x 1 timber or some Y 12 rod to rod the concrete down the hole.
And once you start the block filling, don't stop until finished, or you will tend to have a weak spot at the start stop area. 
Ideally, have an extra pair of hands to hold a board on an angle on top of the blocks so you can simply shovel or pour the concrete down the holes.
I always used a board with 2 bits of flat steel attached/hanging into the blocks, which held the board against the inner edge of the blocks, which made life a lot easier.

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## phild01

https://prod.nrcs.usda.gov/Internet/...1p2_023583.pdf

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## cyclic

Here's a sand and gravel supplier who mixes sand and blue metal for core fill, as opposed to concrete blend.
Actually that jogs the memory back to the last time I used a ready mix delivered core fill, I think it was blue metal mix.  Core Fill & Concrete Blend? There IS a difference! | BC Sands Blog

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## Pulse

there are some really cheap electric concrete vibrators on eBay, I paid $89. works great for this  
Sent from my iPhone using Tapatalk

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