How do I waterproof these concrete pots?

noaddedsugar

I have made a few concrete pots like these for my cacti.http://www.gardenista.com/posts/10-easy-pieces-concrete-small-garden-pots-planters/
Not being much of a dab hand at DIY I waterproofed(or not as it happened) them with a mix of PVA and water. They all cracked within a month :rolleyes: Is there anyway I can waterproof them so they will last? If you could name specific products it would be a big help as I have wandered around B&Q 3 times now and left empty handed looking a lot like this
Thanks

Dublin City Handyman

Look out for, water stop. Costs about 80 a bucket. You could paint the inside of a cardboard box with it and it will hold water.

noaddedsugar

That sounds great thanks! I've found in a 1kg tin which is more pocket friendly. I presume it dries clear?

M.T.D

There is a product that you add to the concrete when you make it that will make it water repellent.
Being waterproof would not really affect whether the pot cracked or not.
The more likely reasons are that the pot was distorted before the concrete fully cured or the concrete mix was not correct.

Dublin City Handyman

noaddedsugar wrote: »

That sounds great thanks! I've found in a 1kg tin which is more pocket friendly. I presume it dries clear?

Unfortunately it doesn't dry clear.. It's gray. If you do decide to use it, tin coats and let it dry.

noaddedsugar

M.T.D wrote: »

There is a product that you add to the concrete when you make it that will make it water repellent.
Being waterproof would not really affect whether the pot cracked or not.
The more likely reasons are that the pot was distorted before the concrete fully cured or the concrete mix was not correct.

Really? I had assumed it was the water because I had left them sitting around for about a month before I got around to planting and it wasn't until I planted them that they cracked. One of them cracked withing 24hrs of the soil being put in and the others weren't far behind :rolleyes:

M.T.D

Water would only be a problem at extremes of temperature. Wet concrete put in a kiln the expanding steam does the damage or really bad frost that freezes the water in the concrete solid but even then only if you have voids that are full of water/ice.

Do you have a picture of your pot/s

noaddedsugar

I threw them out after they cracked on me. I was going to give it another go but wanted to figure out where I was going wrong first. I just realised though that I used cement not concrete, it was ready mix stuff from woodies. Would that have been where I went wrong(can you tell I know nothing about this)?

M.T.D

Concrete is a mix of stones, sand and cement. ratio approx 4:2:1
mortar is sand and cement 3 or 4:1

Sand and cement only, without stones or wire mesh (ferro cement), will crack very easily.
Cement will go off in time mostly due to moisture, goes hard or crumbly. Unfortunately difficult to tell in a bag of ready mixed.

Bonzo Delaney

Is there anything to be said for putting a plastic bag inside them or have I missed the point altogether

noaddedsugar

Thanks for your help, seems I might need to rethink the cement vs concrete. I was using white cement because it is prettier but that doesn't seem to have gotten me very far