Using blocks to reduce amount of concrete needed in foundation.

Frere Jacques

Firstly I must mention, it is the foundation for a BBQ area not a house.
Anywhoo, I want to build a raised area at the end of my patio. I intend to shutter off an area 2'6" x 9' and pour concrete to a depth of 6". Then I am going to build 4 brick tiers on top of which will be mounted an all weather counter and a Belfast sink..Ye get the idea.
Thing is the hobby budget is a bit on the tight side and I have access to a good few flat blocks. My plan is to fill the area with the blocks and fill the rest with a mix up 5:1 sand and cement. My question is, am I in danger of the base cracking during frost because of the different materials in the plint. Assume I can work out any air and the blocks wouldn't be any closer than two inches to any surface.
Also would sand and cement be okay for this job or should I try to get one of those plastic bags of readymix delivered. The area will be exposed to the elements.
Would be glad of any help.
J.

RKQ

Sand, cement and gravel is probably the cheapest of the materials you'll use. I'd recommend mixing your conc on site. It will be easier to dig a 2'6" x 9' base and level it / construct it to a fall if you use conc.

I made a garden path from old blocks 29 years. Its still there today and its still very level. If you decide to use blocks in the base, pack them tightly on well compacted soil (or sand). I'd pour a 3" or 75mm thick screen oven the blocks. 75mm should not crack but again it will depend on the base & the weather.

Frere Jacques

Cheers RKQ.
I was going to pour out an inch or so and then let it off for an hour or two, then bed the blocks in, then mix the rest. Thanks for the tip, I'll make sure I leave 75mm to the top.