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How to get concrete to adhere to existing concrete?

I have this concrete stump that I want to repair and use the tank stand to hold a 1200 lt drinking water only poly tank.

I've started drilling holes into the stump to hold steel reinforcing bars to hold the reinforcing mesh and I thought I saw a product once that I can bush on to help the new concrete attach to the stump.

Do you guys have such a product or with the mesh will the concrete attach plenty good enough.

This stump took a hit with a builder trailer and I removed the broken section to re concrete the stump.

When repaired I'm going to concrete in a base to house the 2 tap Davey pump for when I transfer water between the tanks.

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MitchellMc

Hi @CharlieBear62,

I’m going to be quite cautious here because what you’re describing isn’t just a cosmetic repair. It’s a structural member that will be supporting roughly 1.2 tonnes of water, not including the weight of the tank and stand. That’s a significant load. From a safety standpoint, repairing and grafting a new section onto a damaged concrete post that’s intended to support that kind of weight really falls outside normal DIY territory.

Even if you drill holes and epoxy in reinforcing bar, tie in reinforcing mesh, and use a concrete bonding agent, you still cannot make new standard concrete bond to old concrete in a way that restores the original structural integrity. Bonding agents can help with adhesion for overlays and general repairs, but they do not recreate a monolithic structural pour. The cold joint between old and new concrete will always be a structural weak point, more prone to shear failure, and inherently inferior to a single continuous pour. With a 1200L tank involved, a failure wouldn’t be minor and it could result in collapse, equipment damage, or even injury.

Rather than attempting to graft on a new section, I would strongly recommend replacing the post entirely with one designed for the load, or installing a new engineered footing and post system. I'm not aware of any products that are designed for this purpose. Alternatively, if you are determined to repair it, I would recommend consulting with a structural engineer and having the repair method properly specified. A correctly designed post needs to account not only for compressive load, but also lateral loads such as wind on the tank, dynamic loads from water movement, and vibration from the pump.

Let me tag @Dave-1 and @Nailbag for their thoughts.

Please let me know if you have any questions.

Mitchell

Nailbag

Hi @CharlieBear62

I also share @MitchellMc strong recommendation to replace the post. Its structural integrity has been compromised in what you can see above ground and quite possibly what you can't see below the topsoil line.

Nailbag

Dave-1

Good Morning @CharlieBear62

Yeah, its a remove and replace option, For exactly the same reasons that @MitchellMc has outlined. I would not trust a repair done by a DIYer and would probarlly be cautious over a repair by an engineer. I think the cost of repairing it correctly will outweigh the cost and hassel of replacing that post.

Dave

Noyade

G'day @CharlieBear62

If I were a dentist.

You've lost a significant piece of crown, enamel on two sides (down to the dentin) and what looks like a failed extraction. There looks to be three solid steel bars (threaded?) in the remaining molars - what happened to the steel bar in the broken one?

Where are the holes you drilled? What was your method of repair going to be?

Always curious.

Cheers. 😁

Noyade

A pre-lunch doodle @CharlieBear62

I keep thinking about that stump. There really isn't much left. I can only think of root canal work and I originally thought those exposed steel rods may be the entire column length - but no?

Drilling through the meaty area with something like 16mm diameter and as deep as you can go. And ankascrews on the best side.

Should it shatter with the drilling - then that's the end of it. Build it up and connect with short rods welded to the plate - not too many as you need to tamp down the concrete. Encase it with specrite board formwork.

Pour.

Is it worth it? Probably not.

Cheers.

CharlieBear62

Thanks for the suggestions guys and yes if I was 20 years younger I would replace the stump and at this stage of my life getting someone in to remove it would be too costly.

After lots of YouTubing I found a brilliant site, Waterstop Solutions who do this exact work and they explain how to safely carry out the stump repairs.

I'll also use a BondCrete type product which should do the job and help the new concrete adhere to the stump.

What I will do is weld up a 3mm plate steel sleeve, pour the concrete into that and leave the steel formwork forever in place, seal up a crack in one of the other stumps and apply some quality paint to help seal the old concrete.

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