Getting ready to build concrete slabs to erect 2 - 8x10 HD plastic storage sheds on. I am now spreading, smoothing, and leveling the base pad to put the forms on. I will need to terrace the pad because of the slope of the ground. I will need to finish using and/or moving the load of black cinders to be able to use the area under part of it, possibly for an existing 8x8 shed, if I can salvage it. It will be a while before I finish this part of the project. But, I do need to begin working on the concrete plan. OK, I need to pour 2, hopefully 3, - 4" slabs: 2 - 8x10 and 1 - 8x8. At a yd for the 8x10s and a little less for the 8x8, I'm figuring on 3 yds total to mix and pour in 1 yd pours. I am too cheap, and too old and slow, to consider renting a mixer to do the job. Four days rental will cost as much as buying one. It will probably take me 3 days to mix, pour, and work up the 3 slabs, by my plan. I can buy, then sell a mixer for less than renting one. 94# bags of portland cement cost 2x more at HD here, than at an L.A. HD. It's a 50 mile RT from town. I will not pay to have ready mix delivered. I do not want to deal with buying and hauling sand and gravel aggregate. After checking around about light weight concrete using porous volcanic aggregates, and self leveling/compacting concretes, I am going to look into making a light weight, Self Compacting Concrete [SCC] for the slabs using the black cinders I have sitting here already. All I will need to purchase is form lumber, portland cement, sheep fence rebar, a super plasticizer, and a mixer, as well as the 8x10 sheds. I have looked long and hard at this and have drug it by a lot of people looking for reasons not to it this way. Everybody objects with reasons that do not apply to this usage. If I can get around the real problems, I can make it work. This is a light duty application. A high compressive strength concrete is not needed. The heaviest load it will be carrying is a lawn tractor being parked in one of the sheds on its plastic floor. The other will only be used for tool and general storage. The real problems to be gotten around are with making a consistent pour of SCC while doing it in small batches, plus calculating and measuring the amount of cinders to substitute for the needed sand and aggregate in the mix. My needs are undoubtedly beyond the scope of this forum. But, if there is anyone here with knowledge of SCC and light weight concrete mix design, it would make my plan much easier. But, I can get it figured out on my own, if I can't find anyone knowlegable to pick their brain. The mixers I'm looking at can mix batches of 2.3 or 2.5 cuft. That means that to make a single 1yd slab pour, I'll need to figure out how to make 11 or 12 batches all consistantly the same mixture, and get them done within 30 to 45 min of each other with the complete pour finished in one day. Does this sound reasonable to do? It has put the strike out in. I cannot remove it.