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Is it possible to resurface an exposed aggregate concrete patio? My current patio surface is about 20 years old, and the aggregate has deteriorated a bit and is pretty ugly looking and painful to walk on. Here's a picture:

http://i.imgur.com/xgNSNgS.jpg enter image description here

Resurfacing seems like a good solution, but I'm unsure of how well an overlay would bond to the aggregate stone. Is there a product that might work?

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  • How much room you got to raise the slab? Can you add a couple inches without interfering with anything (ie thresholds, or the drainage of other systems)? Feb 10 at 13:05
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If you don't have to make the overlay "very thin" and the patio is structurally sound, there's not a whole lot of "bonding" needed - a 1-1/2 - 2" thick overlay on a sound, solid concrete substrate will happily sit there, unless it has voids to encourage spalling (by filling with water and freezing) in the winter. As it happens, that looks like a pretty good bet for bonding to (with very exposed aggregate) though it would probably be advisable to pressure-wash it to remove any loose material, and probably also acid-etch it to improve bonding and further clean it up.

Thin is generally harder to do well with masonry materials.

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  • You could also grind the area the amount of grinding can be controlled and make the top of the surface smother. You don't want a slick surface, I have done this with a 9" angle grinder with water and diamond cutters that made a old salt and pepper exposed job look better than new.
    – Ed Beal
    May 14 '16 at 19:21
  • @EdBeal Thanks for the idea. I looked at some pictures of ground exposed aggregate, and I don't think it's my cup of tea. Plus some of this exposed stuff is VERY exposed and would require a lot of grinding, in addition to there being missing pebbles here and there. A nice clean topcoat would be preferable.
    – Jonathan
    May 15 '16 at 0:13
  • @Ecnerwal Thanks for the info. The overlay products I looked at like Mapei and Sakrete (which has bad reviews) mention doing 1/8" max layers. How would I get to a 1-2" thick overlay? Any particular product/system I should look at? Also, aside from pressure washing, any other prep needed that might help like a primer or acid wash (maybe this varies by system)?
    – Jonathan
    May 15 '16 at 0:16
  • I'm basically looking at "pour a thin slab on top of the one you have" where "Thin" is 1-1/2" or so, involving 3/4" minus or 5/8" minus aggregates - if the extra height does not upset anything else about your patio, it gets you back to the realm or normal concrete practices. The "very thin overlay" products you are looking at are a different deal, and ideal for things like resurfacing your basement floor, when another inch could cause problems.
    – Ecnerwal
    May 18 '16 at 1:18
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Avoid resurfacing with new. There is no way to make a permanent chemical bond, water will get in and it will crack out at any thickness that will not interfere with your use of doors and so forth. Don't let anyone tell you otherwise. This is regardless of climate. Don't believe me? Call your local cement supplier (call the company you see on the side of the mixing truck) and ask them.

To answer your specific questions:

  1. Is it possible to resurface an exposed aggregate concrete patio?

Yes.

And since you are not looking into how you do this yourself, I will encourage you to continue with the expectation that you will want to hire a professional for this work. Nasty chemicals and specialized equipment are involved that will easily damage adjacent materials and injure you.

They will grind your surface and wash with muriatic acid, very carefully masking everything around and up to the first floor ceiling plane - plants, siding, glass, everything should be diligently covered with lots of overlap and well taped/sealed seams.

This should be reasonably priced.

  1. Is there a product that might work?

There is no one stop product for restoring both appearance and texture. You will need to mechanically refinish as well as chemically wash to restore eroded concrete and projected aggregate.


Now, do people overlay their patios all the time? Absolutely. This is how a tiled patio works. However, concrete needs the depth for the aggregate to provide the rigidity. You need 2" minimum for concrete, and if you do choose to overlay you will need to do extensive work to ensure the entire surface of your slab freely drains any water so that when water gets under your overlay, it wicks out to the edges. Hot weather causes vapor pressure expansion with trapped water (steam/cool cycles) as much as cold weather causes freeze expansion with trapped water (freeze/thaw cycles). There is no reasonable means to prep a fully cured concrete surface for an overlay under the minimum thickness. Under 2" the aggregate itself becomes the limiting factor. There is nothing to "bite" to with concrete.

To bring it back, my recommendation is to pay a professional to refinish it through grinding and chemical wash, or research doing this for yourself if you want to take on something advanced.

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you must first grind the pea gravel down to get a "level" surface. Clean thoroghly and let dry. apply bonding agent and let cure as per directions. Resurface with several thin coats or use a stampable overlay mix, about 3/8 to 1/2 inch. I recommend Butterfield T1000 Stampable Overlay. It can be integral colored or stained as you like. Then seal it up. Mission accomplished! It may be necessary to rent a scarifier and use it first, then a grinder/polisher to even it up to a level surface. Use a gauge rake or squeegee to lay the product or make one yourself. Good Luck! John Russell, CreteTechnique, Huntsville, AL

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You can easily form the sides 1" above existing grade, or as required to correct standing water and top with a fine grade pea gravel mix. Vibrate, tamp, and screed flat. After proper cure, start rinsing from the porous start point. Bonding agent x helps bonding and deters cracking. Masonry supply sellers can batch various mixture proportions as required in bulk bags or you can hire a pump service. Even thinner than 1" topping mix will work in certain conditions. Good luck

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    Welcome to Home Improvement. Please edit your answer to fix some of the typos, as that will make it much more readable. Also, are you sure that you can lay a 1" or thinner slab on top of an existing slab and that it won't rapidly crack? Even for only foot traffic, that seems mighty thin, especially if the OP lives in a freezing climate.
    – FreeMan
    Feb 8 at 13:20

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