Concrete Mix - Combining different Brands or PSI strength

Hi DIYers -

In one of the 3 bases (where you place the oven on) concrete slab I accidently put one bag of Sacrete High Strength concrete mix ASTM C387 and another bag of the recommended 5000 plus High Strength Concrete Mix 80 pounds by Sakrete.

The 5000 plus went in first, rebar and then the ASTM C387 went in second. Is this OK? Or do I restart that one slab. I sure hope my goof does not cost me more work.

Thanks for your knowledge!

Hi @monty!

Both of the mixes in your photo are “high strength” concrete mixes. The Sakrete High Strength is tested to reach a load strength of 4,000 psi after 28 days curing; the 5,000psi mix obviously reaches 5,000 psi after that cure time.

Data Sheet for Sakrete High Strength Concrete Mix

Your higher-strength concrete went into the lower part of your slab, where it will be spanning the sidewalls of the block base.

But even if you’d used 4,000 psi concrete throughout the slabs, you’d be fine. In other threads on this forum you’ll find similar questions about concrete strength. The answer is that the concrete is intentionally “over-spec’ed”…you want something that sets up stronger than a standard mix, but “stronger” in this context means WAY stronger.

Also - the 5,000psi concrete is actually in the TOP part of your slab section, because the slabs are cast upside-down. Either grade of concrete is WAY more than strong enough to bear the load you’re placing on it.

Bottom line: You’ll be fine!


Thank You!
Thank You!
Thank You!

I have been losing sleep thinking I needed to redo the one slab.



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Could I mix these two?

If so, can I mix them dry?

Those two items are identical products - just different brands.

Many moons ago, when I worked in the materials manufacturing industry we would bag several different brands w/ the same material. So Brand A… Brand B… Brand C… they were all the same product. Many branded bagged items are like this (especially pet food).

But you don’t need to dry-mix them. Just use as normal… So if you are pouring your base slab, start w/ one brand, then finish w/ the other brand. There may be a SLIGHT difference in color, but it would hardly be noticeable to the naked eye. NORMALLY we wouldn’t recommend mixing / blending materials - but in this instance, you have chosen two identical products.

FUN FACT: The machines that fill bags with loose fill / masonry materials can fill a bag with 100lbs of material FASTER than the machine operator can put a new / empty bag on. From an empty bag, to filled, to auto-stacked on a pallet… 10 seconds! The (unlucky) guy that placed empty bags on the filling nozzle during the pouring process had to suit-up in a sealed suit (looked like a space man) and throw bags onto the nozzles just as fast as he could… but as fast as he was… he was never faster than the machine! Not to mention, it was a HIGH turnover position.

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