driveway curing after top cast

[Vintage Veloce]

Just poured the new driveway today.
View media item 63001And we sprayed the top with Topcast Surface Retarder, which etches the surface a little to get the look we want. We pressure wash the Topcast off tomorrow am
We did the front driveway this way and it came out fine.
However, I'm wondering if there would be any advantage to putting a drip line on the driveway after the Topcast is washed off. I'm betting it would be too late to bother with trying to keep it wet since it will be nearly 24 hours after the pour...?

 

[Farrier]

I'm in Ca also. Never in my 40 years have I ever wetted a slab or any flat work I've ever done. Never have seen it done either.

 

[Vintage Veloce]

I have never seen it either, but I keep reading about people elsewhere flooding there slabs. Maybe it's because we have so little water here. At any rate, is there any point if you start 24 hours late? I think probably not...?

 

[Cyberbear]

All concrete using Portland type cement requires 28 days of adequate moisture to reach nearly maximum strength. You do not need to flood the concrete, just keep it wet or very moist during the curing period. Contractors just pour the concrete, it's up to you to properly cure it, they won't send a guy out to wet your slab each day.

 

[DougWil]

Yes keep the surface moist for 3-4 weeks!

 

[DougWil]

I'm in Ca also. Never in my 40 years have I ever wetted a slab or any flat work I've ever done. Never have seen it done either.

If you didn't spray a curing agent on those fresh slabs to seal in the mix water, the slabs or surfaces of those slabs dried out, stopping the curing process, created a lot more surface cracking, slab curling and significantly lowered the final strength and durability of the concrete.

The water shouldn't be more than 20 degrees different temp than the slab or it causes thermal cracking in the surface.


And before anyone calls BS, or I never heard that, read up on it from The Portland Concrete Association, The Ready Mix Association or any good concrete textbook.

 

[Vintage Veloce]

I think people might be missing my question because I wasn't clear. I'm in San Diego, and the concrete with the retarder sat for 24 hours drying. There was no way around that really with the retarder. So the top surface is now dry. Is it still worth wetting?
Everything I have read said to keep it wet continuously.
Also, the surface dries in about 5 minutes, so the only way to keep it wet would be to water it continuously. Here in the San Diego / California drought, that is pretty frowned upon. No way would I do that for a week. Maybe the next two days... I have been watering it this morning by hand every 30 minutes or so.
But I suspect watering, letting it dry, watering again, etc, might be worse than just letting go without water.

 

[DougWil]

The entire slab didn't dry out in 24 hrs, the surface might have and in pulls moisture to the surface from within the slab. Concrete is porous, water and water vapor move through it.

Either keep your slab moist or wet it down good and when the surface is dry enough spray on a curing agent which will seal the moisture in.

You can plastic tarp it, wet carpet or wet burlap etc to keep it wet.

DO NOT LET IT DRY OUT!!

 

[Vintage Veloce]

Carl

The entire slab didn't dry out in 24 hrs, the surface might have and in pulls moisture to the surface from within the slab. Concrete is porous, water and water vapor move through it.

Either keep your slab moist or wet it down good and when the surface is dry enough spray on a curing agent which will seal the moisture in.

You can plastic tarp it, wet carpet or wet burlap etc to keep it wet.

Good answer. If I could I'd keep it wet for a long while, But I'll try and keep it moist for a day or two.

Thanks!
C

 

[rburke65]

Is that what you meant by a 'drip line'? ...... Wetting the concrete?

 

[Vintage Veloce]

Is that what you meant by a 'drip line'? ...... Wetting the concrete?

Drip line / Soaker Hose:
http://www.homedepot.com/p/Miracle-...a-x-125-ft-Soaker-Hose-CMGSP38125FM/206551431

Actually, it didn't work as I hoped. I also tried a sprinkler, but it couldn't be set up for uniform coverage.
Also, I can't let the water to continue to run on it, for various reasons (drought, runnoff regulations, etc.)

Covering the concrete would be the only effective option, but at this point, knowing the other driveway and the foundation came out fine, and that it has already gone 24 hours dry, I'm giving up.

Dougwil's comments are good! But it is true that no-one (or none I have ever seen) in SoCal continuously waters or covers the concrete. Perhaps they make all the mixes with that in mind.

But neighbors who are not allowed to water their lawns, would go nuts if they saw people letting running sprinklers on construction. ;-)

 

[pcmeiners]

"But it is true that no-one (or none I have ever seen) in SoCal does this."
Your highway department and multistory builders do it, if conforming to spec. Either they seal or keep it wet. All you need do is wet it... through down plastic and wet it once in awhile for at least a full week, what is the big deal; just because everyone else wants weak concrete in SC doesn't mean you have to conform to the ignorance.

 

[Vintage Veloce]

"But it is true that no-one (or none I have ever seen) in SoCal does this."
Your highway department and multistory builders do it, if conforming to spec. Either they seal or keep it wet. All you need do is wet it... through down plastic and wet it once in awhile for at least a full week, what is the big deal; just because everyone else wants weak concrete in SC doesn't mean you have to conform to the ignorance.

I wasn't clear, sorry. Builders may use some kind of sealer or special mix, but really, no one in SoCal covers it nor waters it continuously to keep it wet. I've been watching. Certainly not the highway department, city services or multistory builder. My neighbor is leading a giant job this summer at the local elementary school. I'll ask him about sealers or the mix.
The other local high school is putting in a giant new building. No covers or sprinklers on any of their giant new concrete work on either of those builds.

Hey, I AGREE keeping it wet CONTINUOUSLY starting immediately after finishing is the best thing! It is too late for that here, and wasn't possible with the Topcast treatment we wanted. If the data exists, someone please show me where some authority says it is helpful to start watering it after 24 hours have gone by. I googled a lot, and couldn't find anything.

If it helps to water occasionally, I would give it a hose shower after the concrete surface has cooled down in the evening and in the early AM each day.

 

[wssix99]

If the data exists, someone please show me where some authority says it is helpful to start watering it after 24 hours have gone by.

Here you go: http://www.cement.org/for-concrete-.../concrete-construction/curing-in-construction

^ PCA recommends keeping things moist through the first 7 days of curing.

However, I'm wondering if there would be any advantage to putting a drip line on the driveway after the Topcast is washed off.

You should take the drip hose and sprinkler off the driveway. All you need to do is to keep it moist - not soaked. Too much water too soon can erode the surface coating of cement.

I wasn't clear, sorry. Builders may use some kind of sealer or special mix, but really, no one in SoCal covers it nor waters it continuously to keep it wet.

You are correct. Most people do not do this - it's just impractical. The cost of having gardeners tend all this flatwork with hoses for weeks after placing (and inconveniencing the users who need the pavement) would far outweigh the relatively small costs from any associated deterioration from curing au natural.

It's a bigger deal in some places of the country than others. In you area (where God blesses you with near perfect weather every day of the year...) it isn't as big a deal as other parts of the country/world: https://plasticcracks.siue.edu/index.php?unit=Standard&zip=92110

Hey, I AGREE keeping it wet CONTINUOUSLY starting immediately after finishing is the best thing!

The folks who do this in concrete labs have special steam rooms and concrete saunas. Trying to recreate this in the field can be outrageously expensive and end up doing more damage than good.

If it helps to water occasionally, I would give it a hose shower after the concrete surface has cooled down in the evening and in the early AM each day.

This is a good, sensible plan and will help slow down the interior water in the slab from evaporating as fast - probably more important in the AM than the PM.

 

[Vintage Veloce]

Here you go: http://www.cement.org/for-concrete-.../concrete-construction/curing-in-construction

^ PCA recommends keeping things moist through the first 7 days of curing.

This doesn't say anything about starting to wet the concrete after 24 hours of drying. And that was my question. Most of the stuff I have seen about wet curing seem to assume you start immediately after final finishing.
Another good article here:
http://www.nrmca.org/aboutconcrete/cips/11p.pdf
I suspect that after 24 hours drying in hot san diego weather the benefits of keeping the concrete wet or moist are greatly reduced. But I have no real data either way.

You should take the drip hose and sprinkler off the driveway. All you need to do is to keep it moist - not soaked. Too much water too soon can erode the surface coating of cement.

In current daytime weather conditions, the surface is completely dry 15 minutes after removing the sprinkler.

Just saying.

 

[hellrzr]

For part of my job I do concrete inspection. In Iowa the DOT is pouring lots of sidewalk and driveways through towns to conform with Federal ADA standards. When doing this work they simply pour and finish the concrete and then spray with a cure agent and walk away. The concrete drives are opened to cars again after 7 days and is fully cured in 28 days, as noted above. This is for passenger cars, not heavy trucks mind you. You would want to wait for full cure before really loading weight on the slab. In reality the slab can usually be opened in 2-3 days but unless they use a wire to check temperature against a maturity curve, they wait 7 days to be safe. The cure agent acts as a sunscreen to keep the surface from drying out too quickly so the concrete hopefully cures evenly from the middle out. I have never see anyone keep a slap wet ever. I have always seen cure used also so perhaps without a cure some water would help? I can't imagine it would though. My first question is did you ask this question to the guys who did your concrete work? Or perhaps get ahold of the concrete plant and get some insight from them.

 

[matt_i]

If you read the initial instructions on the Dayton Superior etchant, they have a note to cure & seal after the pressure-wash water is gone. The labor-intensive equivalent to curing sealers is to flood with surface-water. So that's what I would do. A drip head is typically 1 gallon per hour. I'd put them every 4 feet or so and let gravity do the work.

Imo by letting the concrete dry on the surface for a day does not totally "lose" the need to keep the concrete hydrated internally and not let the greater pull of evaporation take the water away.

Tl;dr concrete takes 28 days to fully cure, if you missed one day of flooding the surface, get back to it.

 

[wssix99]

This doesn't say anything about starting to wet the concrete after 24 hours of drying. And that was my question. Most of the stuff I have seen about wet curing seem to assume you start immediately after final finishing.

matt_i summed it up well. The thing you are combatting is an intneral process that occurs over time. Missing any short period of time won't be a big deal. You can just get back at it, as normal, when you can.

In current daytime weather conditions, the surface is completely dry 15 minutes after removing the sprinkler.

Just saying.

That's just what you see at the surface - there's goodness inside. As you wet the slab, it's going to soak up the water like a sponge. (Concrete is porous.) The process you are combatting here is water evaporating from the slab. (You want water available to react with the cement and continue to fully harden it during the crutial initial curing period.) By "refilling" that sponge in the morning and afternoon, you are putting excess sacrificial water in to evaporate throughout the day, so that evaporation doesn't rob water and stop the chemical processes you want to keep going on through the curing period:

http://www.cement.org/for-concrete-...12)/lesson-5-so-you-think-concrete-dries-out-

Another good article here:
http://www.nrmca.org/aboutconcrete/cips/11p.pdf
I suspect that after 24 hours drying in hot san diego weather the benefits of keeping the concrete wet or moist are greatly reduced. But I have no real data either way.

You'll see that the article mentions plastic shrinkage cracking. That's the thing that other parts of the country need to worry about more than you do. You'll see from this link I posted above, you are in the green. For zip codes in the yellow or red - THEY need to be much more dillegent about wetting the slab after it cures. Your ambient conditions aren't causing water to evaporate from your slab that aggressively. https://plasticcracks.siue.edu/index...dard&zip=92110 There's no reason why you'd need a constant waterfall across your driveway. A good wetting at periods throughout the day should be just fine.

The other big effect from this evaporation is curling of the slab. This can cause (like it sounds) the slab to curl and other associated cracking. That's caused when the surface close to the ground stays moist longer and cures much stronger than the surface. Our residential slabs are thin (just a few inches) that we also don't need to worry about this too much. (The thin slab evaporates consistently enough.) This is a bigger deal for industrial floors.

 

[Joemctag]

Use clear construction plastic after wetting. Weight down with bricks or boards. Overlap a couple feet at joints. Run past slab edge any cover with some dirt here and there. It holds in the moisture. It’s like a sauna under there maybe run a little water under the plastic every few days if you don’t see condensation anymore thru the plastic. Curing agent’s what contractors do.

 

[ard]

i think the slab is fully cured...

..its been 3.5 years.