Do Sidewalks Need To Be Sealed


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Old 04-20-07, 03:27 PM
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Do Sidewalks Need To Be Sealed

Hello,
My sidewalk was poured two years ago. I never sealed it and this year I got what I think is called spauling. There's about 18 spots where the top 1/8 layer was loose. These spots are now ready to be repaired, but with what? I have a bag of ready mixed sand mix and need just to add some water and perhaps a bit of concrete acrylic fortifyer. Is this recommended? And should I seal the sidewalk afterwards?
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Old 04-20-07, 04:52 PM
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I'm NOT a concrete expert, but would recommend sealing, YES. It isn't that expensive, and will help.

I will let the concrete guys answer your other questions.

Dale
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Old 04-20-07, 05:38 PM
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Do Sidewalks Need To Be Sealed

There could be several causes of the spalling. - Deicers, excess finishing, non-air entrained concrete.

Any "patch" only 1/8" thick probably would not be effective, considering that you should have some sand in the patch for strength and abrasion resistance.

Sealing is of little or any value. Too much can be detrimental. Keep in mind the slab is sitting in moist soil, so coating the top does little good.

Sealers also wear off with traffic.

Dick
 
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Old 04-20-07, 06:14 PM
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I am not saying that concretemasonry is WRONG, because he is in the field, or has been and has seen with his own eyes, but I have read where it DOES help, and is NOT worn off with normal traffic. It in tests has been shown to reach as much a 1/2" down into the concrete, and DOES repell the water. Gravity works, the last time I checked, and unless your walk is sitting in water it should not be holding water, and any water that you can steer away from the walk has to help. Concrete may act as a spouge but wouldn't the sealer prevent such from reaching the surface thus helping to reduce spalling?

I'm NOT trying to pick a fight, just thinking aloud. I learn everyday.

For a test of your own, do a section and a couple years down the road take a look.

Dale
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P.S. I am talking about sealers that penetrate, not those designed to make the surface smooth and shinny.
 
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Old 04-20-07, 07:07 PM
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There are many types of concrete sealers. The types you're likely to find at Lowe's, HD, etc. are film-forming sealers and as Dick said, they are of questionable value and WILL wear off. They are basically a clearcoat paint. True penetrating sealers such as silanes, siloxanes, etc. will be found only at contractor's supply outlets. They work by chemically reacting with the concrete, forming crystals in the microscopic pores, and repel water because there's nowhere for it to soak in. Even penetrating sealers will not soak in 1/2 inch.
In answer to your question: It can't hurt to seal it unless you apply too much. If you are having spalling or flaking problems it may be because of poor concrete, poor finishing, finishers adding too much water, porous aggregate, use of de-icing salts or compounds, etc. Sealing may or may not help, but it probably won't hurt.
If you patch with your sand mix and an acrylic fortifier, or any patch mix for that matter, expect the patches to stand out like a sore thumb. They will never match the exisiting concrete and will usually be a lot darker. If you want uniformity, you may have to resurface the entire slab with something similar to Quikrete Resurfacer. Sorry.

Pecos
 
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Old 04-20-07, 07:10 PM
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Do Sidewalks Need To Be Sealed

Dale - I said "sealing is of little or any".

This is based on many years of experience, construction problems, testing and writing codes and material standards.

You can always read about depth of penetration for penetrating type "sealers". One of the reasons for the large depth of penetration advertised is the low quality and high permeability of the concrete the sealer is applied to. In reality, the penetration in good concrete is very much less.

Some of the penetrating type "sealers" based on the growth of crystals can actually contribute to deterioration if the entrained air is not adequate.

The coating type sealers, when applied in excess of manufacturers instructions, can pose very real problems and cause spalling beause the reduction of vapor permeability that will cause failure due to repeated freeze/thaw cycles. The inability of a sealer to permit the vapor pressure caused by the expansive process of freezing moisture from within and below is one of the main reasons for surface spalling. Even air entrained concrete can spall with too much of a good coating.

rjordan - If your concrete was overfinished, the surface would consist of an excess of rich cement paste that could have been forced off by the inabiity of it to bond to the base concrete and also because it may not permit the pressure from the freezing.

If you have only 18 small scattered spots on a sidewalk, I would just watch and see what happens. Any patching that you do that thin would certainly not match the surrounding area.

If you are really concerened with the the spots, you can try to patch with a fine sand mix. If you apply a bond enhancer to the existing concrete, make sure you use the correct type. Some materials can actually act as a bond breaker if allowed to dry before the concrete patch is placed. Follow the manufacturers instructions completely.
 
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Old 04-20-07, 07:27 PM
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CONCRETEMASONRY, YES, you stated, " sealing is of little or any value", and I said, " I'm NOT saying you are wrong".

I see NOTHING wrong in my dwelling deeper in the the subject like I did. The BAD thing about putting something in print is that the reader does not hear ones tone of voice and can easily mistake such. Age old problem, FOR SURE.


Dale
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Old 04-21-07, 06:28 AM
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Thanks to all.
It appears that sealing is just a temporary cosmetic fix and Concretemasony has brought up a good point about water vapor from below. This past winter, I used some salt that I had stored in a bucket and I do not know what type it was. This may have been the reason for the spalling. I also fault the contractor because my neighbor had concrete work done and its appearance looks superior to mine.
I will visit a concrete distributer to discuss what type mixes are available for sidewalks, the benefits and quality of each.
I will also consider Peco's suggestion of having it resurfaced as long as I can be guaranteed that it will bond and last for 20 years or more.
Just patching it, I agree now that it would be an eyesore.
 
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Old 04-21-07, 06:35 AM
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sealing concrete

I would add that depending on the sealer used and amount applied, it is possible that the sidewalk would become slick when wet. Something to think about.

just my 2 cents
 
 

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