Didn't know magnesium sulfate could do that to a slab until last Tuesday

I was finishing a driveway in Boise and the mix started going off way faster than normal, like 20 minutes early. I thought it was the heat but the ready mix plant said they'd swapped in a different cement source with higher magnesium sulfate content. I looked it up later and apparently that stuff eats away at cured concrete over time if it's not accounted for in the mix design, it's a real problem out here with the local aggregates. I've poured for 11 years and never once thought about checking the mineral report before a pour. The plant guy said they see it mostly on commercial jobs and just add extra fly ash to protect it. Has anyone else run into this or am I just lucky I never got burned on it before? Maybe I should start asking for the mineral breakdown on every order now, or is that overkill?

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