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GLTHFJ60's Garage Chronicles

It's not in the sun, I think it'll be fine. I wet it down a few times, but it's so hot during the initial cure that the water evaporates off in less than 20 minutes. I get that's what the plastic is for, but I'm not concerned.

What would be the benefit of wetting and covering in plastic for that long anyway? If it was in the sun I could see the benefit, but it's not.
 
GLTHFJ60 said:
It's not in the sun, I think it'll be fine. I wet it down a few times, but it's so hot during the initial cure that the water evaporates off in less than 20 minutes. I get that's what the plastic is for, but I'm not concerned.

What would be the benefit of wetting and covering in plastic for that long anyway? If it was in the sun I could see the benefit, but it's not.
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Doesn't need to be in the sun. Portland cement even in a small slab like that will hydrate for several weeks, but generally the first 7-10 days is where you should wet cure or membrane cure to ensure it has enough water continue the reaction. Even a couple old blankets or moving blankets thrown on top and wet down will do the trick.
 
GLTHFJ60 said:
What would be the benefit of wetting and covering in plastic for that long anyway? If it was in the sun I could see the benefit, but it's not.
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The guy I learned my shit from has been doing DIY pours since the 1960s and he swears by the plastic and water over the following week being the most important thing you can do to prevent cracks (in the sort term, shit like bad compaction not withstanding). It's so easy to do I think it's well worth doing.
 
Copy that. I guess it can help the surface cure harder? Some of you guys were telling me it was so thick, so much rebar, and so small that there was no chance it would crack so I didn't think about it, lol

I'll stick something on it tomorrow. Thanks guys.

Edit, remembered I had leftover plastic from the underlayment. Wetted it down again, covered most of it with plastic, and the remainder with a soaked blanket. I'll leave it on for a week, and wet it each day.
 
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GLTHFJ60 said:
What would be the benefit of wetting and covering in plastic for that long anyway? If it was in the sun I could see the benefit, but it's not.
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Concrete continues to gain strength the longer it can cure. Once it dries out, the curing effectively stops.

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So, as the chart shows, if you just allow it to air dry you're likely to only have half the compressive strength (i.e: 4000# concrete becomes 2000# concrete).

Also, if the surface is allowed to dry out in the first few days, that is when you get dusting and scaling because the surface has very little strength. The concrete underneath typically stays a bit moister and has some more strength, but the surface just erodes.

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Wish I had read up on that more before I guess. We'll see how it does after I keep it wet for a week.

It was hard enough to walk on by the morning after I poured. I don't see how it would be possible to keep it moist from that point onwards when it's getting as hot as it is, esp when I guess I should have been wetting it that night when I was asleep. I thought it would be 24-48 hours of cure till I could even walk on it.

It warmed my whole garage up to almost 90* from Friday into Saturday night, the night after I poured it. It felt like walking on concrete that was sitting in the sun all day with how hot it was.
 
Being indoors vs a sidewalk in the sun helps a ton.

You should have thrown some construction plastic (or a tarp, since this is a tiny pour and you probably have one big enough) over it and shot some water under with a garden hose twice a day.

Frankly, for what this is I don't think it'll be an issue. You might get a little wear and tear from engine hoist steel wheels, transmissions falling off the jack and whatnot but it won't add up to anything of consequence in your lifetime since this is a home shop.
 
GLTHFJ60 said:
Wish I had read up on that more before I guess. We'll see how it does after I keep it wet for a week.

It was hard enough to walk on by the morning after I poured. I don't see how it would be possible to keep it moist from that point onwards when it's getting as hot as it is, esp when I guess I should have been wetting it that night when I was asleep. I thought it would be 24-48 hours of cure till I could even walk on it.

It warmed my whole garage up to almost 90* from Friday into Saturday night, the night after I poured it. It felt like walking on concrete that was sitting in the sun all day with how hot it was.
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They make curing blankets and mats that specifically designed to hold water on the concrete surface. For a thin slab like this, plastic works fine and helps slow down evaporation, but it's less ideal than blankets or continuous misting. Membrane cure is a little better than plastic - you spray it on after initial set and it creates a clear membrane on the surface that greatly reduces evaporation. The risk of not doing it on a small slab is mostly going to be strength and surface finish degradation. You'll get spalling like mentioned earlier, or tons of little spider cracks. If the cracking gets really bad, it can lead to the slab just disintegrating years down the road...especially if it's outside and hit with water and freeze/thaw cycles. I really doubt you'll have any problem with what you did there, but still worth keeping it wet for a few days if possible.




In the past, I had some projects with mass concrete (5'+ thick in the smallest dimension) and had to do temperature monitoring and active cooling to keep the differential between the core and surface temperatures within a certain range. Without pumping cooling water through some of them, we'd see crazy high temperatures for well over a month at the middle of some of those pours.
 
Right, I remember reading about the hoover dam having cooling pipes to manage temps for a long time. Extreme example, but same concept.

Thanks for the advice guys, as usual. I'll keep the wet on it for the week and we'll see how it goes. Next time I'll find a better curing solution. No cracks so far and it's not hot like it was, so I feel like it's going to be just fine.

Now to wait until she's cured and finally get this lift installed! Long road to get to this point.
 
bgaidan said:
In the past, I had some projects with mass concrete (5'+ thick in the smallest dimension) and had to do temperature monitoring and active cooling to keep the differential between the core and surface temperatures within a certain range. Without pumping cooling water through some of them, we'd see crazy high temperatures for well over a month at the middle of some of those pours.
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I assume high temps drive the water out which is obviously bad for curing, correct?
 
arse_sidewards said:
I assume high temps drive the water out which is obviously bad for curing, correct?
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No, more of a the extreme temperature differential between the surface and core leads to shrinkage/expansion and cracking. There are cases of mass structures basically crumbling during curing from these stresses. If time isn't a factor, you can manage it by leaving forms on and wrapping the exterior up with insulated blankets. But time is usually a factor so you then add water circulation lines that run through the core and sometimes even chillers. If you can pull the heat out of the core at a similar rate that the surface is losing heat, you can usually get them out of cure within a week or so vs. the 3-4 weeks it could sometimes take without any cooling. I had one project here in NC that didn't call for any active cooling, but we experimented with putting some 4" PVC pipes down the full height of some bridge columns. Just the open top pipes worked like chimneys and actually drew a good bit of heat from the core. We measured the venting temp at like 130 degrees at one point.
 
GLTHFJ60 said:
It's curing very well. I'm contemplating renting a floor sander to refine it further, but I'm not sure yet. Might just refine the two mild high spots that exist with a hand grinder. Idk yet. I'll take some pics with a straight edge in a few days.
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Yes, please. If not for you, then for us. :flipoff2:
 
Just documenting. Didnt have enough blankets I was (the wife was) willing to sacrifice to this cause, so I landed on two blankets and plastic between a few days ago.

It's getting soaked twice a day. The parts under the blankets are staying sopping wet, and the area between the blankets under plastic stays damp.

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GLTHFJ60 said:
Just documenting. Didnt have enough blankets I was (the wife was) willing to sacrifice to this cause, so I landed on two blankets and plastic between a few days ago.

It's getting soaked twice a day. The parts under the blankets are staying sopping wet, and the area between the blankets under plastic stays damp.

PXL_20240904_140312302.MP.jpg
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Bet ya didn't have "Watering the Concrete twice per day" on your Project BINGO Card :lmao:
 
I have to say, I have never been very religious about wetting concrete. I did it, but very half assed. All of my concrete has turned out very good with all most no cracks. (Whether it be garage floor or sidewalks) I did make saw cuts. All of mine has the fibers in it, so that might be the difference. The only rebar in any of mine is in the foundation for my quancet hut walls. (Not the floor)

Maybe it’s just luck or Florida weather.

I suspect you are not going to have any trouble with your attention to detail.
 
ridered3 said:
Bet ya didn't have "Watering the Concrete twice per day" on your Project BINGO Card :lmao:
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I did actually, I just didn't realize how long I needed to do it, nor did I realize the importance of plastic/curing blankets.

I honestly thought the plastic/curing blankets/diligent watering was only necessary for important outdoor flatwork in the dead of southern summer, but I learned through this thread that's not the case.
 
I didn't hydrate my slab enough and it fucked it up. All cut joints curled up significantly, over 6 months time. Like 1" up. Whole floor needs to be ground.
 
GLTHFJ60 said:
I did actually, I just didn't realize how long I needed to do it, nor did I realize the importance of plastic/curing blankets.

I honestly thought the plastic/curing blankets/diligent watering was only necessary for important outdoor flatwork in the dead of southern summer, but I learned through this thread that's not the case.
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Makes sense all around there and I've learned something new regarding watering concrete.
 
rattle_snake said:
I didn't hydrate my slab enough and it fucked it up. All cut joints curled up significantly, over 6 months time. Like 1" up. Whole floor needs to be ground.
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I’ve personally never seen that happen. That’s impressive
 
Made a pattern and laid out the holes for the two columns with a myriad of tapes. Centered the columns side to side in the new pour and each column base landed 12" off each end of the new pour.

Next I proceeded to plow all the holes. Pilot holes to depth then 1" multi flute bit to depth.

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You'll notice the different patterns in the floor now. I checked the flatness of the pour around the columns with a straight edge and found some pretty good humps. I ground those out with a 9" cup grinder on one of my big metabos. Pushed it hard enough to trip a 20amp dedicated circuit, lol. Top handle is to put downward force on the head to cut faster, worked great.

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Verified depth of every hole again, then cleaned each, and epoxied the wej-it anchors in place. Had a little spalling on three of the holes but I feel that it's pretty minor. I think it happened because my hammer hits weren't perfect and/or the bolt I was driving them in with bent, so too much side load was put on. I'll fill with some non shrink grout or something, but it's not a structural problem imo.

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Finally, the epoxy I used. Probably 75% of this went in the holes including mandatory squeeze out. 24 hour cure time at these temps, so Saturday I'll bolt the columns in for the first time.

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A lot of time and effort to get me to this point. I can't wait to put my cruiser in the air for the first time.
 
Fuck yeah. Need to do some adjustments to make it perfect, but fuck yeah. Plan to do the first lift tomorrow.

Edit: torqued all of the gr8 flange head bolts to 150ft/lbs and none of the anchors pulled up. Fuck yeah.

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