I need a concrete/cement expert

[Dal1980]

Hi

I know the diversity on these boards is far and wide and I'm confident there are people who do (or have done) this for a living.

I wanted to level half a floor off in my home garage (garage measures 5m/16.5' x 2.4m/nearly 8', area to concrete 2.3m/7.5' x 2.4m/just under 8')

I originally wanted to use liquid screed but after pricing up that stuff and finding I would need to double layer it as there is a 3cm drop over the floor length (2.3m/7.5') the price soared to figures I wasn't comfortable with. I then tried to find a screed mixer company but the only one that was even willing to travel to my area said that they wouldn't come out for such a small area 0.2m squared. I decided to mix my own.

While at the trade counter buying this stuff one of the customers told me to just mix it dry. I'm definitely no expert in concrete and the shop seemed to trust the guy who looked like he done something like this for a living. 10 bags of building sand and 4 cement bags later I'm on my garage floor mixing the whole thing up. Although the sand was actually quite wet the cement seemed to absorb most of the moisture and I ended up with a damp pile of lose sand and cement. After levelling it and bashing it down I used a plastering float to 'finish' the job. Although there was a lot of pebbles in the concrete mix (just off the sand, not actual pebbles) the finish in a lot of places shows a bit of drag. Anyway I was completely happy with it until the other day (5 days later) I've inspected the area and found that the cement is very crumbly in places and you can quite easily rub a void into it as it's just turning to dust.

At the same time I was putting all this dry mix down, I had a small area to repair and used the same mix but added water this time to make a paste. This has actually set extremely firm and there are no signs of cracking.

Any advice as I fear I'll have a big job on now breaking up my floor and starting again (not to mention the cost of all of this).

In my defence, there isn't much information online about dry concrete mix that I could find and the information I did come across told me that if it clumps together easily then there is enough water. :/

I'll post some pictures from my phone as replies to this post.

Cheers
Dal

[Dal1980]

It does seem quite solid and rubbing in these pitted areas does seem to stop after a couple of mm at a solid base. Maybe I'm worrying about nothing although there is repair work to do on all the pitting.






Here's the original photos of me laying it







Sent from my iPhone using Tapatalk

[lilshawn]

i'm no expert but...i've been doing my own research since this spring i'll be doing my own concrete work.

But, I think since I'd had all the materials there, I would have just gone ahead and mixed up a bunch of batches in a wheelbarrow and done a wet slab.

if it's crumbly it was too dry.

if it's too wet, the concrete looses it's structural strength. but since this is just a slab to help level things out, I would have erred on the side of caution and made it a little wetter just in case. it's not structural in any way.

it also helps while it's curing... to lay plastic over the surface to keep it from drying too fast (may be the case here since the top is crap but the base is good)

[Dal1980]

Thanks lilshawn

Anything I've done in the past even close to this scale would be wet but since the guy at the store seemed very confident in his dry mix choice I went with that. I have used dry mix for laying patio slabs but that really isn't anything like what I'm doing here. I wish I had done a wet mix now but at the time it was either doing it my way or doing it the way I've been told by someone who clearly had experience :/

Problem is, I may have been writing a different post about how I should not have used a wet mix and just went with dry if I had chosen the other. Now I have more experience though

Thanks for the tips.

I'm still hoping that someone spots this post and tells me it'll be ok, you done the right thing lol