Update: The city park job we did in 2021 versus the same mix specs this spring

We poured a walkway in Miller Park back in 2021 using a standard 4000 psi mix with a standard mid-range water reducer. The city just had us do an addition this April, using the exact same specs from the same plant. The finish on the new pour set up almost 20 minutes faster and was noticeably harder to work for the final broom. The only difference the plant mentioned was a switch in their cement supplier about a year ago. Has anyone else run into this with 'identical' mixes behaving differently? Makes me wonder how much the base materials really change year to year.

3 comments

3 Comments

the_cameron29d ago

Yeah, it's like baking a cake with flour from a different mill, lol.

the_kevin29d ago

Man, tell me about it! We had the same thing happen on a warehouse slab last fall. Same mix design, same plant, totally different beast. The crew said it felt like they were fighting it just to get a decent edge. Our plant guy mumbled something about "different quarry" for the rock that season. Makes you realize the spec sheet is only half the story, the actual dirt and rock they drag in that week is the other half.

elizabeth_jackson5d ago

Exactly. The spec sheet is just a recipe, but the ingredients change every time. We had a batch where the sand was just a little finer than usual, and it threw the whole slump off. The finishers were adding water just to keep up, which of course messes with the strength later. It's all about what's in the ground that day, and nobody tells you until you're already pouring.

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