Question about the old rule of thumb for concrete curing time

I was reading a trade journal from the 80s and it said the old 'one day per inch of thickness' for curing is way off for modern mixes. It said with today's additives, a 4 inch slab can be ready for light traffic in like 12 hours under good conditions. I always planned jobs around the old rule. Does anyone still follow the inch-per-day thing, or is that totally outdated now?

4 comments

4 Comments

paige_bell811d ago

I mean, is it really that big of a deal if a slab takes an extra day to cure? @kevin_lane probably has a point about humidity throwing everything off anyway. I still follow the inch-per-day rule for most jobs and haven't had any complaints yet. Sure, modern mixes might say 12 hours, but that's under perfect lab conditions, not on a worksite where it's 90 degrees and the crew's been busting their butts all day. Seems like people overthink this stuff when the old rule still works fine for basic pours.

the_amy2mo ago

That old rule is basically useless now (modern mixes cure way faster).

kevin_lane2mo ago

What about the humidity in your room though? That old rule might be wrong, but something else is probably slowing it down.

garcia.mila2mo ago

The old rule was for basic concrete without any additives. Modern mixes with accelerators can set up much faster, but the full cure for strength still takes weeks. That 12 hour window is just for walking on it, not driving a truck over it. You still need to plan for the full strength gain before putting real weight on it. What kind of mix are you using for your jobs?