I got a builder that was supposed to pour concrete for a shed base. The specifications that the shed company specify for the shed base is a double pour.
The first pour is the initial base.
Then the steel shed is installed, with the horizontal steel bars at the base of the shed bolted into the first concrete base.
Then a second pour is done to level up the base with the height of the steel bars i.e. the height of the final base is the same height as the horizontal steel bars in the frame of the shed. I've attached 2 photos.
The builder did the bare minimum for the first pour, just enough to have something for the shed to be bolted into. And that was all he did (well he was also supposed to build a wall to the side of the shed and plaster it, but you can see he only plastered half of the wall, and badly at that).
The builder disappeared so I'm stuck with an unfinished job, having paid for most of it upfront (I know, big mistake on my part).
I'd decided to finish the job myself instead of paying someone else to do it. I've a ton bag of sand left, and about 1/3 of a bag of sand and gravel mixed (he mixed them, but I think they look more sandy than gravelly). I've 3 bags of cement, but will definitely need more. And more gravel. Because I want to use up the materials I have, I don't want to buy the ready made stuff. I'll hire a mixer for the day. I have a wheelbarrow and shovel. Maybe hire a float too. There are some bags cement that he left out in the rain and they hardened, and are unusable, so I was thinking of getting a lump hammer and breaking up to use as rubble.
Anyway I'm looking for some advice on pouring the concrete as I've never done this myself.
Someone down the pub told me I should put in some rebar to help prevent the concrete from cracking.
Any thoughts on this? The depth (from the sandy/gravelly part in the middle - see photo) to the top of the steel bars is about 120mm. As it's a shed it's only for storage, but nothing too heavy in the there (maybe stuff like bikes, lawnmower, bags of compost, etc.).
Looking for any advice and can provide any additional information. Thanks in advance.