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We're going to cut up and remove a slab. I figured I might as well (attempt to) cut it into rectangles and use it for landscaping. If I wanted to mortar them together like bricks, what should I use? Every time I search for guidance, I get instructions concerning "concrete masonry units" which I'd normally call "cinder blocks".

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I'll have to look into the economics of feet of cut per cement saw blade, but if we make big enough blocks surely it's economical at some point.

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  • You want polymeric sand - Except "the economics of feet of cut per cement saw blade" isn't. That's for demo, not production. If you're producing, make forms and pre cast. Trying to reuse concrete for anything other than fill for a new pour is an economical loss. It's environmentally sound, just not fiscally. Also, now you have to lay basically uneven flagstones as opposed to flat bricks. And if you don't really know what you're doing, that's going to come out like crap. - If it isn't 6" thick and a 100yo bad ass concrete, is it even worth it?
    – Mazura
    Nov 25, 2022 at 4:14
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    @Mazura I'm talking about a wall, specifically a retaining wall where the rough faces will be towards the earth and the gaps filled with gravel, not flat on the ground as pavers, with anchoring to keep it upright in the long term. I'm demolishing the slab regardless, so the cost of cutting the slab neatly is being compared against the cost of destroying the slab by cheaper means + paying to have the cement hauled away + turning around and buying a similar amount of new cement, possibly in block form.
    – gunfulker
    Nov 25, 2022 at 6:37
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    Ah, it's a wall. Ok, I'm onboard then. "If I wanted to mortar them together like bricks, what should I use?" Mortar. Except they're not bricks, they're 'stone'. What type of bonding agent to use for recycled concrete blocks? +1. My guess is Portland cement and expansion strips every 5'~10'; not mortar.
    – Mazura
    Nov 26, 2022 at 1:08
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    Below Damp-proof Course : sand and cement. No lime. What type of mortar for foundation blockwork below ground level? The answer calls it M6.
    – Mazura
    Nov 26, 2022 at 20:31

2 Answers 2

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Cinderblocks are different breeds. They are soft and porous. They are designed to absorb and adhere to mortar.

Concrete has completly different chartacteristics. You can not use mortar to make them adhere with each other.

However, is it possible to make it happen. Yes.

First the hard part. Drill at least one hole if not two in each block. Insert rebaar through both, leaving enough space for the mixture.

To make mixture: Purchase concrete bonding agent and mix it with just cement and sand. Make sure it is thick and before you apply, wet your concrete block.

Now, a more costlier way. There are products called concrete patch and each have different characteristics. They are not cheap. Also fast setting. Nonetheless pay attention to purchase the breed that applies to vertical applicatin. (CONCRETE PATCH VERTICAL APPLICATOIN)

And there you have it.

Take care.

If you like to spend money on adhesives, one that comes to mind is Adiseal. It will stick to concrete and more.

Adiseal

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  • Any thoughts about using construction adhesive intended to glue together landscaping blocks or glue things to cement?
    – gunfulker
    Nov 24, 2022 at 7:26
  • If you like to spend the money on adhesives, one of the best ones is Adiseal. I will post a picture of it in my answer above since I can't insert image here. Nov 25, 2022 at 2:29
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Make sure you keep it wet while cutting.

It will prolong diamond blade life and reduce the dust.

Any kind of mortar will work.

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