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Question DetailsAsked on 7/26/2017

Do I need to do anything about these small cracks in stamped concrete patio before staining?

Do I need to do anything about these small cracks in stamped concrete patio before staining?

I had a patio poured and stamped last fall. There are small cracks from the stamp that are left. Is this normal or was the stamping done wrong or at the wrong time during the pour? Do I need to do anything with the cracks before I stain and seal the patio? Like fill them. This would take some time because the patio is large, but I don't want to mess up and have the stamped texture start to fail.

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3 Answers

Voted Best Answer

BTW - this is actually 2 years old according to AL - your initial post (which I am sorry I did not see at the time when it was pertinent to the work quality) was near 2 years ago -

Unless you specified an open, porous texture finish like you got (which would certainly have a poor life expectancy), that is a sick looking concrete job - looks like they did not float it before stamping, so you got a very rough surface with a lot of air bubbles in it.

Looks like most (though not all) of those cracks are at the control joints - looks to me like they either did not put release agent on the stamps and/or did it a bit too late, when the concrete was already too stiff so instead of shaping the concrete at the joint ridges on the forms, it pushed down partly-cured concrete and broke it off as the form was pushed down and then removed. Looks to me like the stamping may have been held off about 15 minutes too long, offhand. Or if there is one good area, maybe they had inadequate number of stamps so by the time they got to the other side of the large patio, the curing has progressed too far.

Because some of them are in the main field, it also looks like they did not properly cure the concrete - looks like it surface dried too fast before it could cure, so you got a crusty weak surface layer. [Contrary to popular knowledge, portland cement - ordinary concrete - cures by absorbing moisture to form the minerals which crwate the bond in the concrete - not by "drying" like a lot of glues and adhesives and such. So premature drying, placing in hot or windy drying weather without taking measure, or not damp/wet curing it properly causes weak and highly frost-susceptible concrete.

Unless you intend to put an overlay over the entire surface, I cannot see practically repairing small cracks like that - will probably look pretty bad if you do, like concrete worms if you do that. Don't know if I would repair it - though if looking at having it stained and sealed then you are putting more money into a poor job, so while I certainly would not guarantee the result I would probably (depending on a close on-site inspection) recommend (particularly if in area with true winters) putting on an epoxy modified flowable grout surface repair thin overlay (maybe broomed on to provide traction surface if desired), which would also provide a uniform appearance before the staining along with filling of voids and cracks so the staining would give a uniform result when it was done after the overlay cured completely.

However - given that you originally siad this was a sloppy job and had footprints and handprints and such, I would not put a lot of money into it without an expert opinion about the overall concrete quality - because if badly microcracked or poorly cured short of a total overlay or total replacement, might be putting good money after bad. Sorry.

Here are a few more previous questions about similar issues:

Answered 3 years ago by LCD


Here are some pictures of what I am talking about.

Answered 3 years ago by mole



Thanks for the answer. That was not my post 2 years ago I just posted my images to the wrong post. Thanks anyway for the answers because they are what I was looking for. The contractor said after the fact that it was curing faster than he thought it would and did not have enough stamps, so it got a little dry before he was done. I watched them and they did trawl it and use release powder and rented all the stamps available. Just a big job and bad planning.


Answered 2 years ago by mole


OK - nothing serious that I see and your explanation of what happened matches what I see in the photos - and a common problem with concrete stamping because typically they only use 3-6 stamps even for larger jobs. On larger commercial jobs they use multiple pours separating each truckload by one to a couple of hours to allow time for the stamping to progress without the concrete setting up before they get to it, but that results in concrete waste as there will some left over that is not enough for the next panel so it has to be wasted unless they have some curbing or such formed and ready to be poured, so not the practice on household size jobs where only 1-2 truckloads are being used. Some higher end contractors doing precise intricate or narrow walk stamping or stamping with concurrent staining use a small portable drum mixer to mix just a quarter to an eighth of a cubic yard or so at a time to have the concrete available just when it is needed.

For your repair, which you can do yourself (or if was evident shortly after the job wwas complete could force contractor to come and do at no added charge) - in addition to wire brushing or using a scrap piece of concrete to "burnish" the joints to remove the pieces flaking off (like using a pumice block to dress stone or pavers), since this looks like bare concrete (uncolored), you could then, if you wanted and after cleaning it well, use a wallpaper or paint brush and plain portland cement (normal sack is 94# but many places sell 1-5# repair or patching portland cement grout bags without sand or aggregate) mixed to pancake batter thickness with water and then dab/wipe it into the damaged areas with the brush or even with a rag or by hand (use rubber gloves) to force it into the cracks, then wipe off the excess with a rag or with the brush - causing pits and the minor cracks to be filled, so gives a cleaner appearance.

Note because the new cement will have different weathering, repairs will look a bit darker color for several years unless you use a very thin portland cement to "whitewash" the entire surface with a paint-thick coating - not enough to leave a layer (which would peel easily) but juast enough to color the surface like if you were lightly faux staining, so keep it in the cracks only if you want to avoid that.

Whichever way you do it, try to keep the surface visibly damp for a day after the repair - by sprinkling every few hours, or after the initial set (typically 1/2 hour or so after putting it on - when it is no longer gooey and will not take finger indentations any more so it does not wash off or take a tarp impression) by misting gently with a hose or by putting a tarp over it to keep the moisture in (wet underneath every 4-6 hours anyway) - realizing that the tarp surface will get cement on it which will not come off easy.

Of course, try a small spot first and let dry a full day to be sure the color mismatch is acceptable to you if only doing the impression / joint areas.

Doing this will reduce the flaking along the joints, and marginally reduce long-term degradation from water getting into the cracks and causing wetting-drying or freeze-thaw spalling, but from what you showed would not be expected to significantly affect the stamped appearance of the patio when viewed casually walking around - is a micro view, not a macro issue.

Answered 2 years ago by LCD

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