Viewing a single comment thread. View all comments

hostile_washbowl t1_j6g5jm8 wrote

Did you follow the instructions on the amount of water to use?

3

md9918 OP t1_j6g9dub wrote

I did-- if my measurement was off, it wasn't by much. I had this happen before when doing some under-slab plumbing repairs for a new shower, but chalked it up to not troweling it much. I guess from a liability standpoint they'd rather have people mix it too stiff and retain the strength of the concrete, than too loose, and have it be brittle and break.

4

hostile_washbowl t1_j6gas99 wrote

If you mix it too stiff or too loose is when you run into strength issues. It looks like you only use about half the water needed.

Sorry but I’m gonna have to blame the user on this one.

5

Banana_Ram_You t1_j6gm0a2 wrote

I don't know anything about concrete, but given the existence of the post, and the tray of mix looking like sand... I can only concur

8

KRed75 t1_j6h1jbz wrote

That looks about right with the water. The less water the stronger the concrete will become when fully cured. It shouldn't have any dry mix, however.

−1

hostile_washbowl t1_j6h1lwv wrote

If it has dry mix then it doesnt have the right amount of water

Anyways looks like they added water to the mix versus adding the mix to the water which results in a bad blend

4

KRed75 t1_j6h99um wrote

It's mixed correctly in the photo. OP just didn't work the surface enough with a trowel or float to smooth it out.

Here's how properly mixed concrete should look which is what I'm seeing in OPs photos. If it's visibly wet it has too much water.

2

hostile_washbowl t1_j6i22ev wrote

Yep. Based on that video, OP used too little water. The dry mix is not fully saturated (or ‘damp’).

0

Engatsu t1_j6j8x4t wrote

So don't add water to concrete mix for max strength... Gotcha

1

KRed75 t1_j6ke9m9 wrote

Not sure how you got that out of my post seeing as I said It shouldn't have any dry mix.

1

jimmio92 t1_j6gt1wr wrote

I find it's best not to read the instructions at all. If you've ever seen concrete pours done on TV, you know the consistency you want -- partially melted ice cream made of rock. Add a little water at a time until you're there, stirring, folding, and kneading the whole time with a shovel. Shovel it in the cleaned out hole, smooth the surface, bingo.

Mix more than you think you need -- worst case scenario, you got yourself a boat anchor, but you had enough to finish the job and that's what matters.

What you're at now is "hammer and chisel it all out and start again" -- make sure to use eye protection and gloves.

−1

KRed75 t1_j6h28s7 wrote

Nope. That would be way too much water. The least amount of water the better. The reason you see it so watered down is because it's easier to work with but it's wrong and makes for a very weak concrete that will crack and crumble in a few years. They make plasticizer additives that once added will make what looks like an almost dry mix look and act like it has 2 times too much water.

Check out this youtube video where they take a super dry mix, add a tiny bit of plasticizer and within a few seconds of mixing, it looks like someone dumped a gallon of water in it.

3

syco54645 t1_j6jjntg wrote

That is incredible. Thanks for sharing!

2

KRed75 t1_j6khee7 wrote

Plasticizer in concrete is like magic as the video shows. By the downvotes I've been getting, It's clear that there's a huge misconception that concrete should have so much water that it's liquid to do its job properly which is completely false. The more water, the weaker concrete becomes. It's harder to work when there's not a lot of water though which is why one should use plasticizer instead of adding more water.

Powder plasticizer is best because it has a much longer shelf life. liquid plasticizer has a very short shelf life. If one buys it from a big box store, one should check the expiration date because it won't work if it's much older than that expiration date. The liquid plasticizer at most big box stores is long ago expired.

I used to own a construction business and to keep cost down, I bought a concrete business and a drywall business. Actually made more money off those doing jobs for other companies than I did building houses but I'm an expert in everything concrete. Most companies would water down their mix and add too much aggregate and sand to save money. That's wrong and that's fraud. We did it correctly and would use plasticizer if doing jobs that required nice finish work such as counter tops or concrete walls that were to be the visible finished product. Lots of vibration is needed as well to eliminate voids.

2