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[Mr. Maple]

 Getting ready to make the forms for the concrete slab for the furnace, what strength(psi) should I be looking at  for a furnace that could potentially weigh between 5-6000 lbs once set in place with water?Also, should I give it the full 28 days curing before setting the furnace on?
Thanks

[mlappin]

How good your base is goes a long ways to how good your cement is. If you have clay you might want to replace some of it with sand or gravel.

No point in pouring a high strength concrete if your base is going to settle.

A 6 bag mix should be plenty strong.

[Steinacher Sales]

Mr. Maple,

Your concrete supplier should be able to help you with recommendations of the concrete. That's what they do.

Hope this helps

Greg Steinacher
618-401-0726
www.midwestoutdoorfurnace.com

[dirtdigger]

How thick is the concrete going to be, how much and what size rebar are you putting in, and what's the subsoil you have, solid bedrock or a swampy bog? 

As for 28 days to cure the concrete, that's a new one for me, we've poured many a thousand of yards of concrete and have never waited that long to do anything with concrete, including buildings on top of foundations or drive loaded cement trucks and semi's on new concrete to get at the next pour.    If its half way warm out, a few days is all that's needed to cure about any concrete, week tops.   

As for what strength, five or six bag mix is plenty, some would even go with a four bag mix, personally I like five bag mix for most everything.  I'd also go six inches thick for a furnace slab or use 2x6 lumber for forms which is about 5.5 inches thick.