Author: chogan@directresearch.com

 

In this post, I start in on repairing my badly deteriorated asphalt driveway.

In a nutshell:  I want to patch some badly deteriorated areas in my asphalt driveway.  My locally-available options for doing that boil down to using an asphalt-based “cold patch” that may or may not cure fully, but will remain flexible when driven over, and is relatively inexpensive.  Or, alternatively, using a cement-based or water-curing material, which will cure rapidly to a hard (but potentially brittle) state, and costs somewhat to considerably more.

None of which matters until I get the areas completely cleaned up and ready to be patched.  Which is probably where most of the work is in this task.

Sometimes I get into a task, only to spend a lot of time wishing I hadn’t.  Where I hear myself thinking ” … should have left well-enough alone” … ”  … the more I work, the worse it looks.”

So it goes for me, fixing my driveway.

This is going to take a while.  This part is mostly just figuring out where to start.

Scroll to the end to see my first attempt:  Lowe’s QPR cold patch over paver base filler.

 

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Some stuff about patching asphalt

This section is intended to be everything I need to know about asphalt patching, but never wanted to ask.

But first:  ass-fault or ash-fault?  I say ass-fault, but ash-fault is a common pronunciation of this word, based on what I hear on YouTube.   Maybe that pronunciation developed because ass-fault sounds vulgar?

In any case, I cannot see the mischievous second “h” in asphalt.  Presumably it’s hanging out with the third “i” in mischievous.  So it’s ass-fault to me.

Stuff I think I have learned about fixing my deteriorated asphalt driveway.

Fact 1:  There are many different types of asphalt damage, each of which has its own specialized solution.  The stuff that will fix big cracks won’t fix small cracks, and vice-versa.  The stuff designed to seal the surface (paint-layer deep or skim-coat deep) won’t help with existing structural defects in the pavement.

You can get by with merely filling (skim-coating) the cracks in alligatored pavement only if the pavement is otherwise sound.  But once it gets to the point of having a distorted pavement surface and/or chunks missing here and there, you ain’t gonna fix that with any pour-over-and-spread-out stuff.

And then there are structural problems, which I’ll define as occurring any time the asphalt surface has moved, relative to where it was originally.  That includes anything from open potholes to what I have, depressions in the pavement.

Fixing outright through-the-pavement potholes is its own area.  You can fill deep holes with gravel, but only angular gravel, not pea gravel or other rounded stone.  Then cap with cold patch.

I don’t want to make it out like it’s rocket surgery.  But any idea of “we just spread magic goop over the surface, let it dry, and all is fixed” — that immediately goes out the window. 

A quick fix is pure fantasy, once pavement has deteriorated to the extent that mine has.  That’s really the only clear point.  This may involve a lot of work and several different repair techniques.

Aside 1:  Why not replace it?  The pavement is badly enough messed up, over a large enough area, to warrant wholesale replacement of a large (e.g., 150 square foot) section.  Cost aside, in my case, I don’t want to do a top-notch professional repair that replacement implies, because this house isn’t going to be here very long.  It will be torn down and replaced by something bigger when we sell it, just another part of the “tear-down boom” in Vienna VA.

As to the cost?  I have no idea what it would cost to have 150 square feet of asphalt torn up and replaced with hot asphalt, by a pro.  That said, for the more expensive DIY patch option (Aquaphalt), the roughly $130 per cubic foot cost rapidly adds up on large project.  (By contrast, both Lowes and Home Depot sell more traditional cold patches for roughly $30-$45 a cubic foot or so.)

Aside 2:  In my case, why not just tear (some of) it out entirely, rather than fix it, and replace with (e.g.) flower beds?  Not a bad concept, but this area is quite flat, and adjacent to my house, so I think I’m better off leaving it all paved.  But I can see where getting rid of pavement would be the better solution in other places or contexts.

Fact 2:  For a D-I-Y repair of a large area, we’re talking “cold patch” asphalt repair.  Roads are made from hot asphalt.  Professionals may do asphalt repairs using hot asphalt.

For a DIY repair, by contrast, I need something I can buy in a bag or bucket at the hardware store.  That something is termed cold patch, or maybe cold asphalt patch, or maybe cold-patch asphalt.  You buy a bag (or bags) of it, pour it into place, tamp it down (plus or minus driving over it), and let it cure and harden.  When you’re done, it looks like asphalt.

Fact 3:  Do I have to dig up the existing pavement?  Some types of cold patch — say, Sakrete carried by Home Depot — want to be put in a hole cut through the existing pavement.  Sakrete clearly states that its cold patch material must be contained by the sides of the hole.  Unstated, to me the implication is that if not, it will spread (squish) in use.

Removing the old pavement and installing a full-thickness asphalt patch is undoubtedly a technically superior approach. Obviously better from an engineering standpoint.  But it ain’t gonna happen here.  Not with this much pavement.  Not by hand, with a pickaxe and shovel.

By contrast, QPR (Lowe’s) seems to imply that it can be used to patch on top of existing asphalt.  At least, the three-step directions from the manufacturer seem to imply it.  I’ve found one apparently satisfied YouTuber who filled a driveway divot with that technique, using QPR.

That’s the direction I’m headed.

Fact 3.5:  Everybody says the patch must tie into undamaged pavement.  Whether you remove the deteriorated pavement, or patch on top of it, everybody agrees that the edges of the hole/patch need to be anchored in sound pavement.  I’m not exactly sure why, but that seems reasonable to me.

Fact 4:  Cold patch cure time varies hugely by type of patching material.  On one end is Aquaphalt, a product that is activated by water and hardens completely in a reported 15 minutes.  At the other end is the stuff sold by Lowe’s (QPR), which, even under ideal circumstances, may have a tarry surface for days, and may take months before cured to full hardness throughout.  E.g., instructions say to wait on-order-of three months before seal-coating over it.

And just to keep it interesting, there are reports of stuff that never cures.  Or, at least, reports of people who gave up and shoveled up an attempted asphalt patch when the material they used did not cure to their satisfaction.  At this point, I have no idea whether that might be due to user error, or whether you can get a “bad” batch of cold patch that will not, in fact, cure, even if used correctly.

Finally, it’s not entirely clear what “cured” means in this context.  The traditional cold patch mixes (i.e., not Aquaphalt) apparently cure from the outside in, so curing occurs in stages.  At some other point, the surface becomes dry to the touch and can be driven over, but if you turn your wheels while stopped on it, it’ll tear it up. At some point, the surface is hard and non-oily, but the interior remains somewhat pliable.   And so on.

What I’m saying is that for traditional cold-patch mixes (not Aquaphalt), there is not necessarily any point at which you can say that it’s cured, period.  And whatever your endpoint is, it could take a while (as in months) to get there.

Fact 5:  Cold patch cost varies widely.  The rapid-curing Aquaphalt runs about $130 a cubic foot.  At the other end is the Sakrete from Home Depot, and QPR from Lowe’s, which seem to run around $30 to $45 a cubic foot.

And gravel, of the sort which might be recommended for filling holes prior to capping them with cold patch, runs around $13 a cubic foot, per the Home Depot price per bag.

6:  Can you patch in layers, patch-over-patch?  I don’t know.  For a fairly extensive area like this, I’d like to be able to start in some small area, then expand when possible.  Putting aside whether or not that’s advisable, it’s not clear that you can do this and expect the patch to succeed.  The key issue for me is whether you can build the patch up in layers, or whether you want to get to the finished surface of the patched roadway in a single go.

Sakrete advertises that you can lay hot asphalt right overtop their material.  All of them (in various formulations) suggest compacting the cold patch material with every inch of depth.  But nobody just flat tells me that you can lay successive 1″ deep patches over one another, letting each layer cure before adding the next.  I think that’s Just Not Done.  Possibly for a good reason.

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My cold patch options, distilled.

For dealing with the big areas of unsound, alligatored pavement, using stuff I can buy locally, my options seem to shape up like this.

1.  Not Sakrete, because I don’t want to dig out all that old pavement.  I’m taking the manufacturer at their word that you must install this in a hole, and by implication, you can’t use this to spread on top of existing pavement.
2. QPR from Lowe’s might work in this surface-patch role.  That said, there appears to be some curing risk with that product, including a tarry top surface for days, and a three-month wait before seal-coating over it.  (It can be driven over immediately.)
3. Aquaphalt (Ace Hardware, locally for me), which seems to be a superior product in every way, but costs four times as much as the more traditional alternatives.  Looks like I can use it for surface patching (i.e., without digging up the old pavement), and it cures fully in just a few minutes.  (A further downside, though, is that it comes in plastic pails, so if I use a lot of it, I’ll then have a stack of plastic pails to get rid of.)
4. Rapid Set (Home Depot) is a different water-curing patch with no tamping required.  It’s a cement-based product that sets up quickly.  Just mix it and pour it, much like concrete.  Cost $25 for 50 pounds, versus about $18 for that amount of the QPR brand.  Also comes in a twice-as-expensive version that can be laid as thin as 1/8″.

More systematically, if I look at all the products that are in stock at my three local hardware stores (Home Depot, Lowe’s, Ace), and tabulate the type of product and rating, it looks like this:

Now the picture snaps into a fairly clear focus.  You have two basic options:  Cement-based/water-cure patches, and asphalt-based or apply-in-all-weather patches.

The cement-based/water-cure patches cost more, but they get higher ratings, and most importantly, have far fewer “thumbs down” one-star ratings.  Near as I can tell, that’s due almost entirely to the fact that the cement based or water cure patches cure almost immediately, versus the long curing time of the asphalt-based products.  Most of those one-star ratings for asphalt-based products were complaints that the product either never cured, or took too long to cure.  Secondarily, they were complaints that the top surface remained soft enough to scar (with turning car tires, say) after curing.

Of the cement-based products, the Rapid-Set from Home Depot seems to check all the boxes.  It’s highly rated, it’s reasonably cheap, and needs no tamping.  You basically mix it up and trowel it in like cement.  And it comes in bags, like cement, so there’s no stack of plastic buckets to toss out when I’m done.

In fact, based on the pictures on the Home Depot website, I’m pretty sure that’s concrete with black colorant added.  And the bag says it’s fiber-reinforced concrete.  Here’s the manufacturer’s picture of the asphalt patch being applied:

Source: Home Depot

Yeah, that’s concrete.

And, as a bonus, there’s a separate product (Rapid Set Asphalt Resurfacer), twice as expensive per pound, that claims it can be applied in layers as thin as 1/8″.  So, plausibly, I could feather the edges of my patches with that.

I note, however, that the Aquaphalt water-cured product must be something other that concrete, because you’re supposed to tamp it in.  The products that are colored concrete don’t seem to require tamping down.

At this point, I wonder if I might be just as well off by buying bagged concrete and black concrete dye.  I note that the Sakrete fiber-reinforced high-strength concrete is less than $7 for 50 pounds.  A bottle of dye costs $10, and will dye at least one bag of concrete.  (But you only have to dye the very top layer, so I would only need a few bottles of dye).

Maybe the cheapest and most durable fix is just to fill the defects in my asphalt driveway with concrete.  In the end, I’m going to spread seal coating over the entire thing anyway.  It really won’t much matter if the color of the concrete doesn’t match the color of the existing asphalt.

 

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One big patch, or several smaller ones?

To cut to the chase, several smaller ones.  That’s mostly because one big patch, across all that alligatored pavement, is more than I can reasonably do.  So I’m going to patch this piecemeal.

One argument against one big patch is the amount of material required.  Bringing the entire damaged pavement area up to level would take something like 60 bags or buckets of cold patch.  Those bags and buckets are 50 to 60 pounds apiece.  Cost aside, that just a lot of material to move around.

A second argument is that one big patch would mean I’d have to walk on the surface of the patch more-or-less right away.  So if the compound remains tarry on top for a while, that’s going to be a mess.  I’d rather do smaller areas, so I can walk around them as they cure.

If they cure.

For a third thing, I’m not sure this is going to work at all, so I’d like to start small, if possible.  Or, at least, at some scale well below the roughly 150 square feet that the alligatored pavement encompasses.

After looking at my driveway for a few days, particularly during today’s rain, I’ve decided that hydrology conquers all.  If the rain doesn’t run off it, I’m eventually going to have a bigger problem anyway.   This means I’m going to focus on filling in the puddles first, with the idea of getting the surface to drain.

If nothing else, a puddle with an alligatored-asphalt bottom effectively injects water under the pavement.  That’s an unambiguously bad thing.  So big puddles have to go, one way or the other.

I’m going to start with the deepest puddle.  And stop when I’m tired of messing with this.

Aside from “will it cure up”, the only big unknown is the extent to which I can stack patches.  Once I settle on a puddle, can I fill it halfway with cold patch, then come back months later and finish it to level?  (Assuming no layer is thinner than, say, half an inch).  Or, once I take on a puddle, do I need to fill that from the bottom of the depression up to where I want the repaired road level to be?

I found no answer to this on the internet, which strongly suggests to me that nobody even thinks about doing this in layers.  You should compact it in one- or two-inch layers (lifts).  But then keep on going, in one session, until you get it as thick as you need.  That’s how I interpret what I’m (not) seeing.  Near as I can tell, nobody suggests putting this on in (say) 1″ thick layers, and allowing those to cure, until you reach the desired height.

This fill-the-puddles approach violates the rule that the patch should tie into undamaged pavement.  The puddles themselves are surrounded with alligatored pavement.  But if I cover all of that, I’m back to putting one huge patch over the entire area.

So I will worry about what to do with the alligatored margins of those puddle holes at a later step.

Summary:  Work expands exponentially.

Near as I can tell, dealing with old, worn-out asphalt is like dealing with old chipping paint.  All the work is in the surface prep.  Most YouTube videos on this topic either start with pavement nicer than mine, or gloss over the work required for the surface prep.

At this point, I’ve cleaned the surface of the driveway about as much as I care to.  I’ve shoveled off the plants with a sharpened cement shovel.  Hosed off the surface a few times.  Used a weed-whacker on the residual plants.  Swept.  Picked up loose rocks.  Used a broom-squeegee to move silt and mud out of the deepest parts.

When the puddle pictured above dries, I’m going to place (likely) bags of QPR (from Lowes) in the depression, one after another.  Based on my calculation, three ought to fill that depression right up to where the water fills it in a hard rain.

Then I’ll leave that to cure.  And see what happens next.

Alternatively, there’s a lot to be said for concrete.  So I might be better off opting for some mix of filling the puddles with standard fiber-reinforced concrete, and topping that with the Rapid-Set asphalt patch.  Which is just some variation of high-strength fiber-reinforced concrete with black dye added.

Given the length, age, and condition of the driveway, I could make a second career out of trying to fix all of its faults.  But I have to start somewhere.  And stop at some point.

Either way, I’m going to see if this no-digging approach will solve my problem.  That is, putting a thin layer of some sort of cold patch, in an area of depressed, most-clean, badly alligatored pavement.  Three bags of QPR from Lowe’s ought to cost around $54 and weigh about 150 pounds.   Three bags of Rapid Set from Home Depot would cost $75 and weigh the same.

Either way, that’s a nice size to test all this out and see how well it works for me.

If I really screw it up, I can always call in a pro, get it all torn out, and have it fixed correctly.

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Addendum:  Test patch, QPR over paver base

This morning I decided to test QPR cold-patch on a puddle/hole in the back portion of my driveway.

I’d say it turned out well.  If it will stay put and cure, this will do.

Above, that was a shallow depression in the asphalt, this morning.  Now it’s a level asphalt patch, using Lowe’s QPR asphalt patch placed over a paver-base filler.  Like so:

After sleeping on this problem, I realized the following:

No to concrete.  Thin layers of concrete-based products, over asphalt, would not work well.  Asphalt is slightly flexible, concrete is not.  That’s a recipe for having the concrete crumble when driven over.  Further, concrete shrinks as it dries, which would tend to break the bond with the underlying asphalt.  As a pothole-filler, concrete-based products make sense.  As a surface patch, on top of existing asphalt, they do not.

No to thick layers of asphalt.  The big unknown for the asphalt products is cure time.  (Or, worst case, whether or not they will eventually cure.) I figure that, if nothing else, the thicker the layer of asphalt cold patch, the longer it will take to cure.  (My vague understanding is that they cure based on exposure to the air, so at the very least, I don’t want a three-inch-thick surface-laid layer of asphalt cold-patch.)

Compacted paver base as hole filler.  Because I want a thin patch, but I have some deep holes, I decided to fill my test hole in two parts.  After sweeping the existing asphalt, I filled the hole with paver base to within an inch of being level with the surrounding pavement.  (Paver base is a mix of sand and gravel that is made to be compacted to a firm base, to support weight.)  I then shoveled, raked, and swept that into just the shape I wanted.  I used a straightedge across the hole to check the height.  Then I compacted it with a tamper.

I’m counting on the existing cracks in the pavement to form a natural drain at the bottom of the hole.  Any water that works its way below the patch will drain away, instead of puddling (and freezing) and popping the patch off.  At least, that’s my theory.

A final advantage of this approach is that you don’t need to have the bottom of the hole clean, just the edges.  As long as there’s no loose or compressible material, just bury the silt and such in the bottom of the hole with paver base (or crushed rock, or whatever you are using to fill the hole).

In hindsight, the Lowe’s paver base had larger gravel than I would have liked.  I may switch to the Home Depot alternative before I do the next hole.

Cap with an inch of QPR cold patch.  Aim for a uniform layer of QPR that covers the paver base and extends beyond it to make contact with the old asphalt.  The hope is that a thin, uniform layer of the stuff will cure quicker and more surely than a thick layer of it.  I’d guess that the QPR cold patch contacts the old asphalt in a band about six inches wide, all around the rim of the patch. My hope is that this is enough contact area to keep the patch glued in place.

The QPR cold-patch asphalt exceeded my expectations in many ways.  After reading all the horror stories in various comment sections, I thought I was in for a real sh#t show.  Instead — perhaps owing to my ability to follow directions — it was a pleasant and compliant material to work with.

First, Lowe’s had a fresh pallet of nice, clean bags of it, so there was no mess transporting it.  Second, it spreads well and did not stick to my tools.  Third, it’s easy to know when you’ve tamped it enough, because a) the sound of the tamper changes from a muffled thud — like pounding on dirt — to a “bang”, as if you were pounding on pavement, and b) the feel of the tamper changes from a soft landing to a hard landing. All told, you have more than enough feedback to know when you’ve tamped enough, as long as you pay attention to it.

My sole advice would be to take your time tamping.  It takes a fair bit of pounding to reach the point where the patch “pings” all over when you pound it.  You want no dead spots.  Angle the tamper as you tamp the edges.

In this use, QPR seems to spread naturally to an edge thickness of around half-an-inch.  I’ve read the same in comments on the Lowe’s website, so I don’t think that’s anything unique about my approach.  This, despite doing my best to feather the edge by angling the tamper as I tamped the edge.  I’ve read comments where individuals then take tar-type (melt-able) crack filler and go around the edge of the patch with that, to feather the edge more finely down to the level of the rest of the pavement.

Finally, I did as suggested and ran over the patch with my car, after first covering the patch with thin plywood.  I learned that a) yep, that works, it was definitely flatter after that, b) you really need a piece of plywood that can cover the whole patch and once, c) too small a piece will leave a mark in the patch where the edge of the plywood hits, and d) you can just pound out most of that mark with a tamper.

I tried walking on it, and it’s already strong enough for that.  But I suspect that if I walked on the very edges of the patch, they’d move.  (Unsurprising, as it has had no time to set, at all).  I’m just going to leave it alone now and see how it does.  The surface remains just slightly tacky.  Again, unsurprising, as it’s had all of about 15 minutes to cure.

This is never going to look perfect, but it already looks a lot better than the puddle it replaces.  All-in-all, for less than $25 in materials, and having to buy a new tool (the tamper), this looks like an adequate asphalt patch.

Will it cure?  Will it last? All I can do is wait and see.  I’m tempted to dive right into the main repair.  But maybe I’ll see how the test patch looks a week from now, before I proceed further.

So far, so good.