I want to pour a concrete pad to use as a base for a low structure to hide my trash cans, from both my neighbors eyes and the racoons that like to chew holes in them.

Here's my idea. Dig down six inches, build the forms and add 2" of gravel and 4" of concrete. This area would be 8' long by 6' wide. Then add more concrete to the rear 3' x 8' area to an additional 2" of thickness. I would use this higher area as the actual base for my trash storage building and the lower 3' in front would be an apron to keep my feet out of the mud. My question - pour them separately or together? If the former roughly how long would it take for the first 4" to stiffen up sufficiently for me to pour the rest? I know the air temperature that day will affect the time but a ballpark figure would help.

I hope I have been clear in my evplanation. Thanks in advance.

I don't really understand why you would want the 2" lip for the cans to sit on. What is that actually going to do or gain?
I would just slope a min 1/4' per lineal foot of slope to the front way easier.

This should be poured as one piece and not in two pours. The 2" is to thin and will break up especially if water gets under it and freezes
Hears a good way to form it if that's what you want
Use a 2x8 to form the sides ( and back if you need a form there ) That gives you 7 1/4 in height for the total height of 7'
Use a 2x4 in the very front for the 4" thick apron
For the 2" step for the cans, ripp down a 2x4 to 2' and that goes between the 2x8 sides as the 2"step form. You will need to brace the front of the 2" step form to the lower 2x4 very front form.
To do this brace take some 8 inch scabs 2bys and screw them perpendicular to the outside front form every 16 to 18' This will be a attachment point to back brace/kickers to the top of the 2' step form. This will allow you to get a trowel under the brace when you finish the apron front form
In the middle of the higher step make a higher flat mound of stone 2" higher to use less concrete and keep the stone away from the 2x8 side forms so it will show all concrete profile on the sides.\ and use less concrete. Besides the cans doesn't need 7" of crete under it.
You should have 4" of gravel or 3" min under the slab. 2" is not enough for the water to drain out a seep in the ground. When that happens the slab will heave when water freezes under it if thats your Geo
I'm showing here about 3/4 yards of concrete to fill that form up. A yard places 46,656 cubic inches of concrete. If you are going to mix this by hand use HOT water to help speed the setting time along. Its a lot of premix bags to mix up.
We have 3yd min concede trucks here just for kicks call your concrete Co. and ask for 3/4 yd at 4,000 PSI with hot water and 2% accelerator or 3% if it between 35 and 40degrees with no sun hitting it. Get a 6 mil poly sheet to cover it overnight to keep the top from freezing or frost. If the Geo There is in the lower 20s at night throw some old blankets on top of the poly.
On a side note I would make the step 3 1/2" high and just use a 2x4 for that form and not have to rip down the 2by
PS I do this for a living, you need at least two people to mix this all up. There are small electric concrete mixers to rent to mix this up

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