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I finally checked the slump on 40 year old bridge concrete and the number floored me
I was reading through some old job notes my uncle left behind from a bridge deck pour off I-35 near Waco back in 1983, and his slump was listed at 2 inches. That seemed crazy low to me, so I looked up the old mix designs he had stapled in there and it turns out they were running way stiffer mud than most of us pour today. Now here is where I want you all to weigh in. Some guys I talk to say we got softer because the admixtures and pumps got better, so we push slump to 5 or 6 and still get good strength. Other guys swear this is why we see more shrinkage cracks and curling on slabs, and that we should be going back toward those old stiff mixes. I honestly don't know which side I land on. Was your grandpa or your old foreman pouring it that stiff, and did those decks hold up better than what we pour now?
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david56217d ago
Man, I feel you on this one. My old foreman talked about pouring bridge decks back in the day with a 2 or 3 inch slump and they'd be out there with vibrators working it into every corner. You can't hardly do that now with the schedules everybody runs and the pumps pushing mud a hundred feet up. I don't know if the old stiff stuff was actually better or if we just remember it that way because the ones that failed got torn out and forgot about. But you're not wrong for wondering, it's a real question and I don't think anybody has a clean answer.
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emery19917d ago
Doubting @david562's slump numbers, 2 inch decks were rare even back then.
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