Around here, seems everyone has their asphalt driveway sealed every two to five years. As far as I can tell, this involves spraying the whole thing with a thinned down coating of tar. The biggest benefit of this seems to be tar all over your shoes, your dog’s paws, your carpets, your steps, and your car’s floor mats. Maybe I’m missing something.
What exactly does the sealer accomplish?
Replies
In my area, more people use an acrylic sealer: makes the asphalt last longer and look better too.
Phill Giles
The Unionville Woodwright
Unionville, Ontario
it is intended to seal all the little cracks that form naturally and help prevent water from getting in there and thereby keep them from becoming big cracks and end up a broken mess.
mainly it just makes things look good and black again.
So, why does a driveway need it, whereas a road doesn't?
some communities do re-seal roads, but they tend to use a more gravel-rich mix. Also, they often wait until the cracks are over a certain size then send out the caulking truck crew and seal them all up with squiggly lines of tar.
Honestly, aside from sealing up against water penetration I think its mainly to make it look pretty again!
Norm
Our county is sealing all asphalt roads with a slurry mix - not aggregate, but a lime/tar blend (or a mineral similar to lime) - it's applied hot, the solids are dumped from bags into a mixer that blend the solids with tar. It is then applied through multiple nozzles across the road width rather quickly - it dries in minutes and can be driven on within a half hour. It is liquid enough to penetrate all the hairline and larger cracks on the road yet gives a relatively smooth road surface.
The asphalt coating that homeowners use can vary greatly in quality - it should have sufficient solids (many times sand) and a good grade of tar to really provide an impervious surface. Some of the stuff is so thin that it really doesn't have good crack filling capability.
Remember, it is virtually impossible to repair an asphalt surface to its original condition - get a pot hole or a penetration to install a pipe and it will always be there. That's why some jurisdictions won't allow contractors to trench across a road and instead have to use directional boring to cross under the paving without penetrations. It's hard to find, but tar and chip is great (yes the chips are loose when first applied but clean up after the first week) - it can be easily repaired and is really cheaper that asphalt. Problem is paving contractors can't make as much money so they are usually very resistive to tar and chip. And of course, concrete is the ultimate and roller compacted cement may be the new fashion once the small contractors understand how to mix and apply it.