A concreting question.

[artme]

I have done a lot of concrete work over the years - shovelling sand and gravel and cement into barrows
and mixers; barrowing ready mix to the required spot, rough screeding etc. Never good at finishing so left
that to the experts,

Never gave much thought to design of jobs as that was all done for me.

Now I have a path to lay. Simple enough except for the following factors:

The path will be next to my shed. A good mate dug out the required area and the result is a bit of a quandary
about what to do. The shed slab has a concrete beam all around it and the whole mas sits atop the naturally
slight slope of the block. viewing the profile of the excavation along the side of the shed shows 100mm of concrete floor.
about 100mm of concrete beam and then the rather moist earth layer that increases from about 100mm to 2oomm
in thickness as it runs down the slab.

I intend to put a path of about 80mm thickness butting up to the shed but following the gentle slope of the block to allow for water run off.

Now, I will need to build a small wall, about 100mm wide, against the layers of soil and concrete beam that will join with the path in one continuous piece.

I am wondering whether I should excavate a further 100-150mm down against the shed so that that wall has a good footing and whether I should
use reo, at least for the length of the path, in that wall to path joining area. I envisage the reo being bent at right angles to be placed in the wall and the path.

Any suggetions please??

[Boringgeoff]

Hi Art, the way I see it you have three options, I'll start with the easy one and it's also how I'd do the job if it was my shed. Done in two stages, form and pour the small wall with reo and a footing extending about 100mm below the base of path. Next day pour the path. Disadvantage is that you'll have a cold joint between the little wall and the path, but you would anyway if you were pouring the path against the shed without the wall.
Method two would be to bend your reo as you said and suspend your formwork for the wall either from above or by pegs driven into the ground. this will result in a jointless path/wall but even with reo it will possibly crack along there anyway. Disadvantages of this method is you have to be able to pull the formwork off to trowel the strip remaining at the junction of the wall and path not to mention the plugging the peg holes.
Method 3 by far the hardest, requiring a high degree of skill is to cove the concrete up from the path to the wall as you go. The consistency of the concrete is critical, too wet and it'll slump down and bag and look like crept and too dry will be almost impossible to trowel up into a wall.
Hope this helps.
Geoff.

[artme]

Many thanks Geoff!!

I have been thinking this through for a few days and asked quetions of those with some concreting knowhow.

I have come to realise that your solution #1 is the go - for all the reasons you state. I might go down 150mm
and make the wall 150mm wide to give it bulk and strength.

Just a question on the mix. I have a trailer load of sand and gravel mix and some bages of cement powder.

I am looking at a true 5: mix to do this job. Is this Strong enough?

Many thanks, artme.

[Bob38S]

Unless the path is pinned to the existing floor you will not only get cracking but through moisture, soil movement, dust and debris getting into the crack you will have separation. It is even possible that the path could rise up or fall.

My first step would be to drill into the existing concrete and chemset in a series of rebar pins. Chemset safe not that expensive anymore and will ensure that the path will remain where you want it to be. It may develop a hairline crack at the join but shouldn't separate and should remain level.

An extra, avoid making the path too smooth, ie a steel finish, it's on the side of a shed, will get wet and could become very slippery over time. Brooming the finish tends to be very obvious and can be quite "rough" in places which captures dust and can quickly become mouldy. I prefer to use a large sponge, it's slower but you get an excellent finish, like the 3 bears, not too smooth, not too rough but just right.

Just a thought.

[Superbunny]

Last thing, don't add too much water to your mix so it flows better, it will make the concrete weaker, you need it to flow into the area and be workable but not a sea of dirty water with a bit of sand and rock mixed in. Concrete hydrates i.e. heats up and gives off water when it dries or goes off as they say, it also obsorbs moisture from the air and surrounding soil to set, you can evan pour concrete under water quite well if you know what your doing. To make small amounts of concrete flow better just add some dishwashing liquid to the mix.

SB

[artme]

Thaks Bob and SB.

I had intended to broom the finish as I do not want a dead smooth surpace.

As for pinning I had thought of that too My main problem with this is that if I pin into the beam I may not have enough material surrounding the pin
in the beam. I measured the beam today at100mm.

I may be wrong - frequently am - but if I have the wall "floating"separately to the path then cracking along the joint will not be an issue.

Judging by the state of the existing concrete in the shed area up and down movement is minimal or non existent.

[springwater]

If I was still working in concrete we'd pin into the existing slab, can be a mongrel job especially down low but went to ensure against a call back later but seeing you're doing it the pros n cons are up to you. Take it easy what ever you do.

[artme]

If I was still working in concrete we'd pin into the existing slab, can be a mongrel job especially down low but went to ensure against a call back later but seeing you're doing it the pros n cons are up to you. Take it easy what ever you do.

Understood Springy bu the path is to be set below the level of the slab to all ow water to run off donwn the slope and not into the pool area.

Pinning to the existing slab is not really an option because of this. The most pinning I MIGHT be able to do is to pin the wall to the beam as described above.

Thanks for your post every little bit helps.

[springwater]

Oops sorry, thanks, just pin anything you can to whatever you can.

[artme]

Well I got the formwork up for the wall today. Decided Against reo and will use a mix of 5:1 premix to cement.
Ought to be strong enough.

Was lucky enough to have a plank about 4metres long and exactly the right width for the job. A couple of Old stair treads
completed the length and the formwork for the step Jus had to fabricate some pieces for the rest of the step area.

Lots of time saved by having the big timber!!

I'l take some photos and see if I can post them. Never had any real success with photos but I shall try again.

[Boringgeoff]

Artme, it's probably too late because you've already started mixing the concrete, but you really need a bit of reo or mesh in there. Regardless of the strength of the concrete a big part of that strength is provided by the mesh. I've seen wire netting used in an old path and the renovator told me it was a real pain to break up.
Cheers,
Geoff.

[Bob38S]

Would have to agree with Geoff.

Reo doesn't cost the earth but can make an enormous difference down the track.

[artme]

Bugger!! Job done camera battery flat. phone flat.

Went ahead without reo. Just have to wait and see.

Job looks good, I'm buggered. Don't ever want to see a concrete mixer this side of my grave again!!!