How to fix quick set concrete that didnt set?

[AlisonT]

I’ve had a bit of a landscaping fail - I’m trying to build a very small retaining wall using one course of besser blocks capped with a layer of bricks, to hold back the edge of a sloping driveway. It’s really only a foot or so high and in a very low traffic location. 

I put out three bags of quickset for my few metres of dug out channel, settled the besser blocks in it and shaped the concrete mix up against the blocks to act as footings, then watered in with 8L of water. 

I’ve come out today and the mix is like damp sand, not set at all. 

Did I use too much water or not enough, or was Quickset not the right option? Should I have soaked the bricks first to avoid them sucking up the water? And what should I do now to fix it? 

All suggestions gratefully received!

[JacobZ]

Hi @AlisonT,

Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.

While I much prefer premixing concrete in a wheelbarrow or bucket to ensure there is no potential for any concrete to go unmixed. When premixed, the amount of water you've used is about right for quickset, however, if it is poured over the top of dry mix, there is no guarantee that it has penetrated all the way through.

Can you upload some photos of the result and advise what specific mix you used? 

This will help me offer a solution moving forward.

Let me know if you need a hand uploading images, I'm happy to help if required.

Jacob

[AlisonT]

Thanks Jacob, much appreciated!

Totally see your point about quickset’s pitfalls, I was rushing a small job and thought it would be less faffing around this way but have learned my lesson. 

It was the Bastion quickset mix: https://www.bunnings.com.au/bastion-20kg-quik-set-concrete_p0760335?store=7369&gad_source=1&gbraid=0...

 

[JacobZ]

Hi @AlisonT,

Unfortunately, that looks like a pocket of sand and aggregate with very little cement powder to bind it together. Pockets like this can happen in premixed concrete and it is why it is always best to mix the concrete with water before putting it in place. This ensure you get a homogenous mix where sand, cement and aggregate are present all throughout.

You're going to have to remove it and replace it with new concrete that gets mixed in a bucket or wheelbarrow.

Let me know if you have any further questions.

Jacob

[AlisonT]

Thanks Jacob much appreciated!