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Thread: Does a concrete driveway need to be sealed?

  1. #1
    Join Date
    Dec 2004
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    Does a concrete driveway need to be sealed?

    Had a new concrete driveway put in last year. My wife remembered that they talked about sealing it this Fall. After pricing sealers at HD (I'll need almost 2000 sq ft worth), I'm hoping that it isn't really necessary. Is it? Will it significantly increase the life of the concrete? By helping avoid cracking, spalling etc? Hopefully it isn't something that needs to be done regularly.

    Any guidance appreciated.

  2. #2
    Yes, the driveway definately will need to be sealed. I found out the hard way after pressure washing my drive and not sealing it. The sealer closes up holes in the driveway and prevents water from freezing and cracking in the driveway.


    Highly recommended.


    Wallace

  3. #3
    Gary, I could stand corrected, but I think the only real benefit from sealing a concrete slab is to help prevent stains and such. Sealer manufacturers will also tell you it protects from road salts and acids and a host of other evil and vile things (some of which are probably true), but as far as preventing spalling and other actual concrete failures, I don't think it adds any benefit to what you already get from a good curing compound (applied to the freshly-finished concrete).

    Of course, this is assuming the concrete was properly finished and cured in the first place. If the mix was too wet, or the finishers got a bit lazy and souped up the finish, it's a case of spalling waiting to happen, especially in a freezing climate. Sealer might help delay the problem, but I don't know if it'd completely eliminate it. In cases like Wallace mentioned, it sounds like the finish might have been a bit punky on the surface (usually from too much finishing water) and the pressure washer exacerbated the problem. Sealer very well might have helped prevent the problem, or at least slowed it down.

    I've inspected over half a million square feet of concrete slab used for aircraft parking aprons (before, during and after the pour), and unless they did it years after I left the job, that slab has not been sealed to this day. (The joints, yes, but not the slab.) It's in a freezing climate, and it's held up well, but it is stained. It was also placed and finished by a commercial crew building to pretty stiff slump and PSI specs. Homebuilders might not take as much care (or have a guy like me getting paid to watch them. )

    I guess the main criteria (besides the expense) is how important the stain resistance of this slab is to you. If you intend to use a pressure washer on it, sealer might buy a bit of protection.

    Hope this helps -

    - Vaughn

  4. #4
    YES!

    Every winter, I think about doing it, but get lazy. I've lived in freezing/snow climates, and this is what happens.

    Cold, frozen slab... Park car in driveway... Engine heat melts snow... Concrete absorbes melted snow... Refreezes... Frozen slab crumbles... Result = pitted concrete...

    This is what it will look like in two years of a frost climate...
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  5. #5
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    YUP! It is a good idea to get a couple of coats of nasty, solvent based sealant. It should last 2-5 years. I currently have 2 coats on mine and it is still shiny from the coating.

    Dan
    A flute without holes, is not a flute. A donut without a hole, is a Danish.

  6. #6
    Quote Originally Posted by Scott Parks
    ... Concrete absorbes melted snow...
    This is what it will look like in two years of a frost climate...
    Scott, you're right about melted snow infiltrating the concrete surface, freezing, then causing the spalling you showed in your picture. But...the fact that the moisture is getting absorbed into the surface is the result of how the concrete was finished and/or the concrete mix design used. Not all concrete has such a porous surface. As I mentioned earlier, I've been involved in the placement of lots of unsealed slabs, all of which have been exposed to freezing weather (and much heavier wheel loads than your typical driveway) and these slabshave not spalled over the past 15+ years. (And they have an intentionally rough surface, which you'd think would make them more prone to absorbing water.)

    Spalling is the result of a bad finish (technique) or concrete mix (materials), and no sealer that I know of will fix these problems. I was discussing this yesterday with my dad (a P.E. Civil Materials Engineer who's been designing concrete mixes and writing concrete specs for about 50 years) and I mentioned Wallace's experience with the pressure washer. In his opinion, a sealer would not have been enough to prevent the washer from washing away the punky surface layer of the slab. To put it in a woodworking perspective, of you put a coat of hard polyurethane over balsa wood, it only makes the wood minimally more resistant to dents. A bit, perhaps, but not much.

    - Vaughn

  7. #7
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    I realize this is an old thread, but the information remains relevant.

    I am no chemist, Nor am I a concrete specialist. That said, it remains thousands of concrete experts who recommend sealing concrete are, probably, not wrong.

    The best quality finishing of the surface of the concrete is not going to change concrete's general characteristics. It will "absorb" water. Were it otherwise, it could not dry and harden, which, experts indicate, can go on for years. Of course, if it can lose moisture in the process of hardening, it stands that it can gain it.

    Regarding moisture gain, it remains water expands when it freezes. As such, water in concrete will expand and cause damage to concrete when it freezes. We see similar action in the rock cliffs that surround my home in Easter Washington, and in other places. Water gets into any opening of the rocks, freezes and pushes the rocks apart.

    Finally, even if perfect mixes and finishing methods did stop or reduce damage, how well was yours mixed and finished?

  8. #8
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    I have never even heard of sealing concrete driveways where I live. I expect it would be much more important where you get hard freezes and salts are put on the surface for melting purposes.

  9. #9
    Since we rarely get much snow at all, it probably isn't a huge deal to seal my driveway, but since I'm going to be resurfacing it this year, I'm going to do it anyhow.

  10. #10
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    It would be interesting to hear from the OP to see if he sealed or not.

    I lived many, many years in Montana, and we got our fair share of cold weather, with lots of warm weather intermixed. Most of my driveways were not sealed, in fact I don't think any of them were. I seldom had any issues with the surface.

  11. #11
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    Retired civil engineer from Michigan here, and I have never specified or heard of sealing exterior concrete surfaces other than applying a curing compound to prevent the surface from drying out before the concrete cures. If it was such a good idea, don't you think the DOT would use it on concrete highways? Most spalling is caused by: improper curing, improper finishing, improper aggregate and/or too much water in the mix. Now, if you saw cut your control joints, you want to properly seal them with an elastomeric caulk over a backer rod before the first freeze/thaw cycle. Otherwise you will get cracking, particularly at the intersection of joints.

    Resurrecting a 12 year old post must be a record.
    Last edited by Ole Anderson; 03-30-2017 at 12:57 AM.
    NOW you tell me...

  12. #12
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    Maybe a record for revival but a good topic.

    I seal my driveway every few years. I have found that the ice does not stick to the concrete as well and seems to reduce any spalling. Given the condition of some of the roads around me, perhaps they should be sealed

  13. #13
    In my brief stint as a concrete inspector I never saw the acreage Vaughan has but I saw enough to know that the caveats in some of these replies are probably the reality. Your driveway is not DOT-spec'd and inspected. Whatever mix was specified had more water added at the site so it would dump and work easier. Then it was floated to death making a nice smooth surface which is nothing but wet sand and cement with the aggregate pushed to the bottom. The rebar or wire mesh that's supposed to hold it together was lying in the mud where it doesn't do its job and will rust. It might have been sloped enough to drain properly and freeze less or maybe not. You shouldn't NEED to seal it. I can't say whether you should or not.

  14. #14
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    I live in Minnesota ad I've only seen sealed concrete a relatively few times. There are miles and miles of sidewalks that was never sealed. My own 35 year old concrete driveway is not sealed and looks bad due to spalling, but I also know the previous owner didn't take care of anything.

    I know of some sidewalks laid by the WPA in the 1930s that still look great to this day. Some of the WPA sidewalks replaced in the 1990s cracked in just a few years.

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