A geezer, a propane torch, and some flammable material. What could possibly go wrong? Continue reading Post #2029: 20 bags of QPR, finishing the repair.
Tag: asphalt patching
Post #1977: Updated: Twenty bags, and done. What I have learned about QPR asphalt cold patch.
With the final patches in place:
Edit 10/6/2024: Below is the final surface, after using some tar-based crack filler and Latex-ite 10-year seal coating. See Post #2029. The seal coat did more-or-less nothing to hide the patch. That said, while it ain’t pretty, it’s a lot better than it was.
This post summarizes what I learned using QPR cold patch (from Lowe’s) on a badly deteriorated section of asphalt driveway. A prior post (Post #1974) explains the situation, and go back to Post #1971 for an assessment of options for patching asphalt. Edit: Post #2029 describes the final steps of crack-fill and seal-coating. One heads up: A squeegee does not work for spreading seal coating on an uneven surface like this.
Above, that may not look so hot to you, but I guarantee you it looks a lot better than it did. Once I seal-coat this, in the fall, I think it’ll be … acceptable. Given how torn up the driveway is. I have no idea yet whether these surface-laid patches will survive the winter, but will update this next spring.
First, it took between 3 and 7 weeks for this to cure fully, in the heat of early summer in Virginia. The reason I’m a little vague is that the patches seemed to be cured after one week. At three weeks, a heat wave (near 100F temperatures) re-activated them, and the surfaces were once again sticky in spots, shedding little tarry bits. At seven weeks, another heat wave (several days at 100F) did nothing. By seven weeks, they were as solid and tar-free as the asphalt they were laid on, despite the heat.
Second, this stuff varies from batch-to-batch. As you can see above, I laid mine down as a series of separate patches. I bought and laid the bags of QPR a few at a time, because that’s all I could handle. From one batch to the next, the QPR material differed in how “liquid-y/tarry” it was, in the final color once set, and to some degree, in the surface finish once set. I’m going to seal-coat this in the fall, so the color variations don’t much matter. But if you doing a big area, and are particular about how this looks, you might want to buy all you need, all at once, from a single batch or lot number.
But arguing against buying a whole lot at once, see the note below on how hard it may be to estimate what you need, if your driveway surface is as un-level and messed-up as this one was.
Big batch-to-batch variation could also explain part of the strong differences of opinion among on-line reviewers of QPR. In my case, if I’d stopped with my first first batch, I’d have said “QPR is a dandy product”, period. With the later batches, that has a huge qualification, that the “walk on it anywhere, any time” cure time is unknown. And all the hassle that can bring, during a hot spell.
Third, foot traffic across these patches makes a mess, due to the tiny little tarry stones that get tracked everywhere. It’s tough to state just how much of a pain those are. The get everywhere. The surface sheds those rocks for the first few days (again, Virginia, early summer), and then starts shedding again if it gets hot, for some weeks thereafter. So if this is going to be laid in place where people walk, either lay it in patches so that people can walk around the newest patches, or maybe lay plastic over it.
Fourth, the manufacturer says you can drive across these patches immediately. And … yeah, technically that’s true. If this were out in the middle of the street, and looks didn’t matter, I’d have no problem with that statement.
But I’d say that’s mistake, if you can avoid it, if you are picky about how the final product looks. In my experience, there’s a risk of marking the pavement surface slightly for the first couple of days, no matter how carefully you drive (i.e., don’t turn the wheels when stopped). And there’s a near-surety of picking up some of the tarry surface stones on your tires for the first few days. Better to stay off these patches as much as possible until they’ve had a few days to cure.
That said, laying down plastic, then thin ply, and driving over that, did seem to compact the surface finish better than I could do with just a tamper. So, drive over the plastic-and-ply protected surface to get the best flat-level surface on the patch. But don’t drive over the unprotected patch for a few days, if you can help it. If you have to, the patch will survive, but you’ll likely ding up the very top surface a bit.
QPR asphalt cold patch.
1: Why QPR.
QPR was a relatively cheap patching material that could be applied overtop the existing asphalt surface. I cannot over-emphasize how much labor that saves, relative to digging up all the alligatored asphalt that was deeply embedded in the clay soil of my driveway. And then applying a much thicker patch of some alternative material. If those patches will just stay stuck down, and don’t get popped up by freeze-thaw this winter, that labor savings alone will make it worthwhile to use QPR over other locally-available materials.
Of the cheap, asphalt-based patching compounds I could buy locally, one (Sackrete, at Home Depot) was for filling deep holes only. It should not be laid atop existing asphalt, per manufacturer’s directions. Using that would have meant digging up all that alligatored asphalt. All of which is firmly embedded in the underlying clay soil, because this broken-up section of driveway had originally been laid directly onto the dirt.
But QPR (Lowes), by contrast, can be laid directly over an existing asphalt surface. At least, that’s my takeaway from the manufacturer’s minimal instructions, and comments on the Lowes website and elsewhere. Obviously, that won’t work if the underlying asphalt itself is subject to movement. But as long as it’s firmly stuck in place, it should fine.
A completely different product, Aquaphalt, is a competitor to QPR that can also be laid directly over an existing asphalt surface. That’s a water-cured patching material that looks like asphalt, but isn’t. And while Aquaphalt appears to be a superior product in almost every way — particularly with a 15-minute cure time — it’s also between three and four times as expensive as QPR, per cubic foot. It also comes in plastic buckets, which then must be disposed of. (I used one bucket of Aquaphalt, on one particularly ugly stretch of pavement. I explain that below.)
2: I used a half-ton of material for this ~105 square foot patch.
Each bag of QPR weighs 50 pounds and costs about $20. Therefore, my 20 bags of QPR weighed half a ton, and cost a little under $400.
On net, for the area I patched, I got about five square feet of surface covered, per bag. But that’s clearly a function of how deep my patch is, on average.
I brought the 50-pound bags of QPR home six to eight at a time, in my hatchback, after lining the back with a plastic sheet.
And it’s a good thing I bought just a few at a time, because I waaaaay over-estimated the amount needed, when I first looked over this section of driveway. Raising the entire sunken driveway surface back to its original level would have taken about 60 bags of the stuff. So instead of raising it to be fully level, I just filled in the low spots (the puddles), and raised it as little as I could, beyond that.
I’d have had a mess on my hands if I’d stockpiled the full 60 bags that I thought I’d need, before I started.
3: Applied in manageable pieces
I put this down over several sessions, over the course of a week and a half.
Each session being maybe three or four bags’ worth of material, applied to one defined section of the driveway.
From start to finish, you:
- sweep the area to be patched,
- haul in a bag of QPR patch,
- Slit the bag bottom, dump the QPR.
- Rake it out/shape it at the edges.
- Haul/slit additional bags as needed.
- Tamp it.
- Tamp it some more.
- Run over it with your car, after covering in plastic and thin plywood.
Some days I went through that two or three times. Most days on which I worked on the driveway, I only did that once.
One full cycle, from sweeping to running it over, seemed to take me about two hours. But that includes some time pondering the situation, wondering what I should do next. Mostly, pondering whether I was maintaining enough slope for water to flow, with the help of a 4-foot level.
In my “puddles first” strategy, the goal was to cover the entire area and not end up with standing water anywhere, after a rain. With that as the goal, it was helpful to have some rain halfway through the patching, so that I could see what puddles remained after I’d filled in the biggest ones.
4: It makes a mess if there’s foot traffic.
At least it did, in my climate (Virginia, typical day in the mid-70s, sunny).
The freshly-laid patch has a tarry surface. It will be stickier or less sticky depending on temperature and age. Fresher and hotter mean tarrier. As long as the patch is still tarry — either because it’s fresh, or it’s a few days old and in the hot sunshine — if you walk on it, you will pick up and track around tiny little tar-covered rock chips. Which then stick to everything.
And that’s a pain in the ass.
5: The tarry top surface of my patches temporarily went away over the course of a week.
(I have now rewritten the intro to reflect what actually happened over the course of seven weeks.)
After a week, in my climate, I could walk cleanly across the patch and not pick up anything.
Before that point, though, in addition to shedding rock chips, the surface of the patch tends to pick up any stray organic matter (e.g., leaves, pine needles, wood chips) that will stick to the tar. I believe this stuff will mostly move along once the surface is no longer tarry. At any rate, the week-old patches were mostly clear of debris.
In principal, these were “ready for car traffic” almost immediately after they’d been fully tamped. But only in the sense that the car tire would not squish the patch, much. But you’d still be well-advised to wait until the next day before driving over these. I think my car treads lifted some surface stones off the patch, when I drove over the patch on the first day.
The upshot is that, as the manufacturer advertises, you can drive right over the patches on Day 1. Don’t stop and turn your wheels. But my take on it is that you shouldn’t drive on the fresh patches if you can avoid it. Your tire treads are going to pull some tarry stones off the top of the patch when you do that. Better to minimize that until the top surface of the patch has had a few days to cure.
The other interesting aspect of aging of the patch is the surface gets smoother over time. I guess it continues to flow a bit. But, for sure, the fresh patch (dark) has a much rougher surface texture than the week-old patch, despite being laid and tamped the same.
6: Pros and cons of doing this piecemeal.
Doing this piecemeal, as I did, has several advantages. First, I don’t think I could have done 20 bags of QPR in one day. Second, I would walk on the older (cured) patches, as I put in the newer (fresh) patches. And I could walk on them as a way to walk around that freshly-laid patching material. Third, the only way I could figure to end up with a reasonably level final product was to fill in the low spots — the puddles — first.
Arguing against this approach are the looks and the time. I believe that the entire patches surface will cure to roughly the same dry and densely-packed finish. But the joins between the individual “batches” of patching will probably remain visible no matter what. But in addition, each fresh patch extends the time during which you’re at risk for tracking tarred stone chips around. For example, I started this more than a week ago, and it’ll be a week from now before the most recent patching material will have a cured, non-tarry surface.
Conclusion
I’m not sure I’d do this again. And I’m not sure I wouldn’t, either.
For me, it boiled down to QPR being the easy and cheap solution. You can drive down to your local hardware store, pick it up by the bag, and (after some significant surface prep) spread over a badly damaged asphalt surface.
This, as opposed to (say) trying to get three bids from pros, to come out, tear that up, and re-lay that section of the driveway correctly. If I could get a pro around here interested in something that small.
The physical labor wasn’t that big a deal as long as you can lift the 50-pound bags. I worked up a sweat tamping it, but I’m not even sore from doing that. (OTOH, I lift weights regularly.)
Sure, it sticks to your tools. And to your shoes. And anything else it comes in contact with. And it stinks faintly of asphalt, for some days afterward. All depending on the temperature. But, given that it basically is asphalt, none of that should be a huge surprise.
I have no idea how well it will last. For now, it all appears to be physically solid and well-attached. This, despite doing my best to apply it as thinly as I could, in some areas. And without the best surface prep in the world.
The individual pieces of the patch give it a little bit of a redneck look. But that should mostly go away as all the patches cure to the same shade and surface finish.
In any case, I have to leave it alone for a couple of months as it cures fully. So I get to look at that patch until August or so. At which point I’ll apply some modern miracle crack filler to any remaining cracks, then top coat the entire pavement.
That’s the plan, anyway.
Addendum: Plus one bucket of Aquaphalt.
I actually started by purchasing a bucket of Aquaphalt 4.0 (smaller stones). That, before I realized how much of this stuff I needed. And how much Aquaphalt would cost to do the entire job.
I ended up using the Aquaphalt on one section of pavement that had been heavily colonized by grasses. Unlike QPR and similar products, Aquaphalt cures by addition of water, and it cures fast (15 minutes) and hard. No tarry mess. I figured that if the grass should try to grow back (despite my heavily salting the area per Post #1973), Aquaphalt would stand a much better chance of keeping the buried grass roots from growing through the pavement than would the slow-to-cure QPR.
Edit 7/19/2024; And, so far, so good. Going on eight weeks later, and nothing is poking up through my asphalt patches. I’m guessing that spraying the alligatored asphalt with a strong salt-water solution, prior to patching, killed the roots of all the vegetation that was there, as intended (Post #1973).
As far as I can tell, other than the high price and the waste stream of plastic buckets, Aquaphalt is a superior product. It spreads and shapes almost as easily as QPR, and seems to stick to the pavement just as well. It cures in 15 minutes, as advertised. The surface finish of the Aquaphalt 4.0 is much finer than that of the QPR, owing mostly to the smaller average gravel size in the Aquaphalt 4.0. The sole downside I noted to Aquaphalt is that it didn’t flow/rake to the edges of the patch as easily as QPR, and I don’t think I was able to lay quite as thin a patch with Aquaphalt as I was with QPR.
Edit 6/5/2024: That’s not quite right. Aquaphalt’s main downside is that it “flows” less well than QPR, at least once you’re at the water-and-compact stage. I ended up leaving marks in the Aquaphalt in areas where the tamper did not hit squarely onto the surface of the Aquaphalt. At the time, I thought I had fixed that by tamping these areas flat. But, in fact, the Aquaphalt’s surface had so little “flow” at that point that it didn’t fill in the little low spots my mis-tamping had created.
But worse, the finer surface finish of Aquaphalt is much less forgiving than the coarser surface finish of QPR. Little imperfections that are lost in the background roughness of the QPR surface finish stand out in the Aquaphalt surface finish.
The moral of the story being that if you are not the best at leaving a smooth surface finish on materials like this, Aquaphalt may not be the better choice, relative to a tarry patch such as QPR. For the reasons described just above.
That’s a lesson that my driveway and I learned the hard way.
Looking on the bright side, the little dings in the Aquaphalt section get lost in the overall unevenness of the patch.
I guess that’s a bright side.
We’ll see how it looks with a seal coat.
Otherwise, if I didn’t care about the expense or the waste stream of big plastic buckets, think I’d do the whole thing in Aquaphalt. It’s as versatile as QPR (in that you can lay it over existing pavement), but lacking all the factors that make QPR a bit of a mess. You also avoid QPR’s months-long wait prior to seal-coating over the patch and roadway.
Edit 6/5/2024: But on a raggedy, roller-coaster asphalt surface such as my driveway, you aren’t going to end up with a beautiful finished surface of Aquaphalt as-seen-on-TV. If nothing else, there’s no flat reference surface to screed to. Unsurprisingly, the finished surface of my driveway — after QPR top coating — is not flat. Plus, making it flat (level) with the remaining sound driveway surface would have required laying down three times as much material as I actually used with a “puddles first” patch-application strategy. I’m pretty sure I’d have done Aquaphalt the same way — in a series of discrete patches — if only because it’s 50 pounds a bucket, and don’t think I could move 1.5 tons of that material in a day. Let alone get it laid, watered, and tamped.
Post #1974: Nine bags down, five to go. What I have learned about QPR cold patch.
I’m learning a few more things about patching my badly deteriorated driveway using QPR cold patch. See just prior posts for background.
See also:
Post #1977: Updated: Twenty bags, and done. What I have learned about QPR asphalt cold patch.
Lesson 1: Day 2, Still tarry when hot
On Day 1, yesterday, these patches were “walk-able”. Nice and firm. I could stand on the edges, as above.
More importantly, I could walk right across them without picking up little tarry stone flakes. (Which would then get carried into the house on my shoes, and make a mess.)
I thought that was the way QPR worked. Ready for traffic immediately, so the manufacturer says.
I was wrong. And the manufacturer meant auto traffic.
Turns out, yesterday was a relatively cool day. Maybe low 70’s F.
By contrast, today, Day 2, is hot and sunny. And the surface of those patches is now tarry, and they are no longer cleanly “walk-able”. I picked up little stray bits of tar as I walk on them. It took me a while to notice that. With everything that implies.
Lesson learned? Don’t walk on the patches yet.
It’s still a matter of faith that these will eventually cure to the point where they are clean to walk on regardless of the temperature. And I can always toss sand or mortar over them if that fails to happen. (But that permanently alters the appearance of the top of the patch, so I’m hoping I don’t have to resort to that.)
The bottom line is that in a warm climate, and in warm sunshine particularly, you can’t count on having a cleanly walkable surface on QPR cold patch for at least a few days.
Lesson 2: Plan your patches accordingly
So, obviously, you need to plan your patches so that you don’t need to walk on them for a while. At least in my climate — USDA Zone 7 in Virginia.
But I didn’t do that. I’m able to walk around on my driveway now purely as a matter of luck.
My patching strategy defaulted to filling in the biggest puddles first. Each patch in the first picture above corresponds to an area of the driveway that formed a puddle when it rained.
Just by chance, the resulting isolated patches give me plenty of old pavement to move around on. I would like to claim that I though of that ahead of time. But I didn’t. It’s purely luck, that filling puddles gave me places to walk on the old asphalt.
Lesson 3: Use in whole-bag increments.
The recommended strategy for getting QPR onto the road surface is to slit the bottom of the bag, pull up on the top (using the handles built into the bag), and let the contents slide out of the bag.
But the contents are a) heavy and b) semi-liquid.
The result is that everything in the bag spills out, and fast. One moment, you have a bag of cold patch sitting on nice clean asphalt. Three seconds later, you have a pile of cold patch on the asphalt, and an empty bag.
As a result, you have to patch in whole-bag increments. Once you open the bag as the manufacturer directs, there’s no going back. Move it around with a shovel, maybe. But one way or the other, you’re placing a whole bag of it somewhere.
Lesson 4: Estimating the quantity needed is harder than you’d think.
It’s not just that the holes to be patched are irregular in shape and depth.
It’s that, with a surface-laid patch, on an irregular (not-flat) driveway surface, you have some leeway on the depth of the resulting patch.
In particular, I’m trying to shape these so that water will drain off my driveway. I want to avoid puddles.
But the driveway slope itself is so low, and varies so much from place-to-place owning to the uneven surface, that shaping the finished patch to do that involves a lot of guesswork. Or, at least, it did for me.
In my case, I ended up using vastly less patching material, so far, than I originally estimated. And that’s because I’m not filling the driveway up to some theoretical original surface level. I’m just filling the puddles enough to get water to flow across it.
I hope. I won’t really know if I’ve succeeded so far until the next hard rain.
Lesson 5: Patch size may be limited by plywood size (4′ width).
Common advice is to do the final tamping of asphalt cold patch by laying down a sheet of plastic, then a piece of thin plywood, then driving over it. I can vouch that this works with QPR. I hand-tamped mine as firmly as I could, then ran it over. Running over it, covered by thin plywood, definitely appears to make the patch surface more compact, and to make the patch more firmly compressed.
If you rely on this method, then the largest patch you can make well is one that can be covered by a sheet of plywood. And that you can conveniently drive your car over.
You can, I guess, finagle it, by sliding the plywood around and only driving on a part of the patch at a time. But that’s asking for the plywood edge to leave an imprint in the patch.
Conclusion
At this point in my driveway rehab, I have filled in the biggest puddles and coincidentally covered up the largest places where pavement was outright missing.
There’s still a lot of badly-alligatored pavement, with chunks of pavement missing, that I don’t quite know what to do with.
Right now, the patches look fine, but are tacky due to the heat and sunshine. Will they cure? Will water flow off the driveway without puddling? Will these patches last?
Making an isolated patch, like the ones above, is easy. The QPR material flows easily at my ambient temperature (say, 75F). And it’s not even tiring, as long as you have the strength to lift the 50 pound bags. Move a bag to a hole, slit it, rake the patch material out flat. pound it flatter. Repeat.
Whether the final patched driveway is going to function well, or look right, I have no clue.
It’s going to be rain and threat of rain for the next few days, so at this point, I’ll let it be until we get some sunnier weather.
Post #1973: Next up in asphalt rehab, salting my driveway.
The background is that I have chosen to repair a badly-deteriorated stretch of asphalt pavement myself, rather than have it properly replaced by a paving professional.
Next step is killing the roots of the plants that were growing in my driveway.
Recap
Above is yesterday’s test using QPR cold asphalt patch.
Unlike its owner, the patch is flat and firm.
Also unlike its owner, a few days of weathering should cure its problem with tackiness.
What’s next?
Next, I’m going to salt my pavement.
This is a completely logical thing to do. As I now explain.
First, to get a good look at the driveway, I shoveled off the surface vegetation, hosed it down, then weed-whacked the residual, and swept. Without that, I would not have realized what poor shape the pavement is in. (N.B., a cement shovel or square-point shovel, filed to a sharp edge, turned out to be the right tool for the task of removing surface vegetation growing through the alligatored driveway pavement.)
My driveway had weeds growing in it because all my prior attempts at killing those weeds failed. My wife objects to the use of Round-Up, and really, to chemical weed killers in general. And I agree, mostly. But in this case, several less-globally-toxic treatments — solarization, vinegar, and one of the more benign weed killers — failed. They knocked the vegetation back temporarily, but it came back.
Second, the roots of those plants are still in the cracks of the pavement, and still alive. They will try to regrow.
But so what? Surely I’ll take care of that when I cover them with asphalt cold patch. I mean, it’s not as if those plants can grow right through fresh pavement, right?
Eh …
Third, I now find out that buried plants, particularly grasses, can grow right through fresh asphalt. As in, grow up through inches of hot-laid asphalt. So my naive notion of patching over them to kill them was …naive.
(FWIW, one good explanation I read is that the binders in fresh asphalt will slowly flow if subjected to steady pressure at a single point. E.g., if I were to place a chest-of-drawers on fresh asphalt, the legs would slowly sink into the surface. Blades of grass will do the same thing, in the opposite direction.)
Fourth, once you’ve chopped off all the greenery, consumer-grade broad-spectrum weed killers are useless for killing plants down to the roots. That is, glyphosphate (Roundup), diquat (Spectracide), glucosinate (Bioadvanced) and similar only work if the plants are green and growing. (That’s my reading of the “mechanism of action” of each of those.) Spraying those chemicals on the root stubs does no good.
Fifth, I have a bag of halite (rock salt, sodium chloride) that’s been kicking around my garage for years. I have no use for it. Yet it was too useful a substance just to throw away. I’d be glad to be rid of it.
Sixth, gardening websites say to use salt as a weed killer with extreme caution. That’s not because it’s particular toxic to humans, but because it effectively poisons the soil long term . Enough salt makes it so that nothing will ever grow there again.
To which I say, that’s not a bug, that’s a feature.
So, I’m going to salt the formerly-overgrown sections of my driveway, before proceeding. The idea is to poison the soil and kill the remaining plant roots. Then I can proceed to patch over the (formerly) weedy sections.
I have combined the two ways that websites suggest using salt as a weed killer.
Websites devoted to pavement suggest sweeping rock salt into the cracks between pavers or bricks, rather than using sand for that purpose. That should keep those cracks weed-free for years. Or so they say.
But gardening websites want you to use salt water. The maximum solubility of salt in water at room temperature is about 360 grams of salt per liter of water (reference). Bagged rock salt (as opposed to a solid chunk of salt) is listed as weighing about 1 kilogram per liter (calculated from this reference). So the saltiest water you can make would require just over 5 cups of salt per gallon of water. I figure a few cups of rock salt, per gallon, should be sufficiently lethal to plants.
So I first broadcast rock salt over the area and swept it into all the cracks. Then I wet down the area with very salty water. I’ll soak it with salt water again later today. And then — under the assumption that the salt will kill anything living in that soil — I can pave over it, once the salt water has dried. I think.
Edit: Next day, in hindsight, just go with salt water, skip spreading the rock salt. The rock salt just makes more work, as I now have to sweep that up before I lay down asphalt patch.
A few other considerations
Let me assume the salt will permanently kill the residual vegetation in this section of my driveway. Here’s a few more things I need to work out.
My alligatored pavement may be too far gone for a thin layer of spread-on goop.
The closer I look at my driveway, the worse it looks. I had hoped to patch the low spots, and apply some sort of squeegeed topcoat to the rest (e.g., Gator-Patch). But the more I look, the more I think I’m going to have to put a thick patch over most of it. There’s too much asphalt already missing.
Patches should ideally be no more than 3′ wide.
Turns out, my limit on the size of an asphalt patch is determined by how far I can comfortably reach with the tamper. The tamper weighs quite a bit, so, for pounding that up and down for an extended period of time, my comfortable reach is the length of my forearm, or about a foot and a half. If I want to stand on old pavement while I tamp the patch, the patch can’t be more than 3′ wide at any point.
I guess I could tamp it “on the fly” — tamp down each bag as I dump it. I guess I could stand on the patch, as I tamp it. But for my test patch, I really liked getting the patch all leveled up in the loose material, from one side to the other, and then pounding it flat. I suspect that with the roller-coaster surface of my driveway, I don’t think I’d end up with something that was level if I tried tamping it on the fly.
Asphalt laid on clay is different from asphalt laid on crushed rock.
As I read through internet advice on how to deal with badly damaged asphalt pavement, I’ve been kind of amazed at how cavalierly many suggest starting by pulling up all of the old, alligatored pavement. I look at my pavement and think, you’ve got to be kidding me. Sure, the asphalt is alligatored, but each piece is firmly embedded in the clay beneath. The surface as a whole still has considerable structural integrity.
Then it hit me: I bet that most internet advice assumes you’re working on properly-constructed asphalt pavement, laid on on a bed of crushed rock. In which case, alligatored pavement would essentially consist of loose chunks of broken-up asphalt with no structural integrity. (And that are easier to remove, to boot.)
So I’m going to trust my instinct on this. The alligatored pavement seems more than sound enough to walk on. There’s nothing loose or moving there. I’m going to limit myself to removing loose stones and earth, and otherwise leaving it alone. I think that the command that all alligatored asphalt should be removed is a good working rule for asphalt what was laid on crushed rock. I question the usefulness of doing that for alligatored asphalt that’s embedded in clay soil.
Pavement base as hole filler, the jury remains out.
If I had all the time in the world, I’d let my test patch sit for a couple of years to see how it holds up. But I don’t. So I need to forge ahead without testing how durable this repair is.
The main structural problem for my asphalt driveway is broad, shallow depressions in the pavement. Not potholes through the pavement. Not fully-formed tire ruts. But places where the asphalt surface has sagged a few inches, where tires of a vehicle might run, or a car might be habitually have been parked.
If I don’t level those out, those will form puddles when it rains. I think the term-of-art is ponding: I have ponding on my driveway. And my understanding is that this is bad, full stop. For example, I don’t think seal coatings will adhere to areas subject to frequent and prolonged ponding. Fixing the alligatored surface, but not fixing the ponding, will just make the ponding more prolonged after each rain.
The upshot is that where the pavement has sunk several inches, I need a broad patch that is several inches deep in the middle.
I think that applying several inches of QPR cold patch is a risk for failure to cure in a timely fashion. As I understand it, the stuff cures through exposure to the air. A thick layer, therefore, should take longer to cure than a thin layer. (But, to be clear, that’s just a guess on my part. I haven’t actually tested that.)
That was the genesis of the idea of applying cold patch over tamped paver base for my test patch. For my test hole, I first filled it to within an inch of the final level with tamped paver base. Then I did my best to cap that with a uniform inch-thick layer of PQR cold patch.
Applying cold patch over compacted paver base, in this application (surface patching of badly damaged asphalt), has three benefits.
First, by capping the deep (paver-base-filled) hole with just an inch of asphalt cold patch, I’m hoping to avoid the dreaded “failure to cure”. But, honestly, unless I test it, I don’t know if the depth of the patch (within reason) matters at all in this regard, as long as you tamp it firmly as you build it up in “lifts”.
Second, fiddling around with paver base is a lot easier, to me, than fiddling around with (messy) asphalt cold patch that sets up over time. Filling the bulk of the hole with paver base lets me do all the “sculpting” of the shape and depth of the patch in sand/gravel mix, first, before I break out the cold patch.
This is fairly important here, because I’m trying to re-construct a level surface over which water can flow. I’m starting from a badly distorted surface with multiple puddles. So the ability to take my time, and construct that new level surface, before anything is set, is a plus.
Basically, it makes the cold patch part of the process easier. After tamping the paver base, I end up with a smooth flat place, in the right shape, at the right height, on which I want to spread an inch of cold patch. All I’m trying to do, with the cold patch, is apply it in a uniform flat layer.
Third, there’s a small cost saving, as it substitutes relatively inexpensive paver base for more-expensive cold patch. Paver base costs about a third of what QPR cold patch costs, per volume. For my test hole, using paver base as the filler cut my use of QPR not-quite-in-half. (Obviously, it’ll vary with, among other things, the depth of the hole being filled.) In the case of my test hole, that works out to … call it a one-quarter reduction in cost per area patched.
But there are some possible downsides to using tamped paver base filler for low spots, under asphalt cold patch.
First, nobody on the internet even mentions the possibility of doing this for surface-patched asphalt. Either it’s too fussy to be used by pros, or pros don’t do this kind of half-assed surface patching, or it’s a bad idea.
Or all three. Or yet something different.
But generally, if nobody does it this way, there’s probably a reason for it.
In my defense, I note that many asphalt crack fillers explicitly tell you to fill a deep crack with sand, and only apply filler to the top half-inch or so. My pounded paver-base plateau is the same concept, just for a larger area.
Second, having a paver-base core means there’s the potential for freeze-thaw damage. If I saturate the paver base with water, and the asphalt below the paver base keeps that from draining, a hard freeze could turn that to ice and heave the patch up. I’m hoping that the patch itself will keep out most of the water, and and that any residual water entry will drain out through the cracks in the asphalt pavement. So I’m not sure I’d try this, if the asphalt at the bottom of the hole is still sound enough to retain water.
The potential for trapped water is a strong argument for making the patch all-asphalt, no matter how deep the dip in the pavement. Asphalt can’t absorb and trap water as paver base can.
Third, the patch has less area to adhere to the road. Done this way, the patch is only stuck to the roadway around its perimeter. Is that enough? The middle of the patch is well-supported against compressive (pushing-down) loads, because compacted paver base will not compress. But it’s more-or-less stuck to sand. It’s not firmly adhered to anything solid, and so is not protected from lifting loads, such as (e.g.) high winds.
Surface patching and water flow: An inch of thickness is a mile, in driveway slope terms.
Surface patches stand above the existing pavement, at least somewhat. So, by definition, they will impede the flow of water off that pavement. Somewhat.
With QPR, I can’t manage to make the edge of the patch any thinner than about half-an-inch. That doesn’t sound like much, but a) water doesn’t flow uphill and b) this driveway section doesn’t have much slope to begin with. I’m guessing 1″ per 8′, or thereabouts.
If nothing else, these raised patch edges will direct the flow of water. So patch edges have to be oriented so as to try to get the driveway to shed water.
Surface patch edge thickness also raises the issue of connecting or overlapping adjacent patches. Based on what I see on YouTube, it should be easy enough to “graft” a fresh patch onto the edge of an existing patch just by placing the cold patch and pounding it out with a tamper. The upshot is that I should be able to do a string of separate patches while still only worrying about a minimum of a half-inch increase in pavement height for the patch.
Patching in layers still seems off the table.
The natural way for me to try to restore the asphalt surface back to its original level is to start by filling in the lowest spots, then working up and outward from there. But I just don’t think that’s a viable approach, because that would require me doing layers of patches, one on top the other, as I built up the surface back to level.
I don’t know if that will work. I don’t know that it won’t. The fact is, nobody talks about doing that — stacking patches vertically. So either it’s a dumb idea, or the typical users of these products does not face the issue I’m facing, with sagged pavement areas.
At any rate, near as I can tell, the approved method is to bring each patch up to the finished pavement level, in one pass. (Maybe several “lifts” or compacted layers to bring the patch to full thickness, but doing those layers all those layers one-after-another until the full required height is reached in a single session.) Coming back later and adding another layer of patching, weeks later, just doesn’t seem to be done.
I’m not sure I can do that, and respect my maximum-three-foot-width rule.
Conclusion
In hindsight, the decision to patch this pavement myself may not have been the best decision I’ve ever made. With pavement this screwed up, there’s a lot to be said for having a pro tear it out and replace it with hot asphalt.
But having started down this path, I’m going to finish it. The results don’t have to look spectacular. I just need a reasonably sound repair.
Post #1971: Dealing with an ageing pavement.
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.
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.
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.
- 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.
- 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.)
- 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.)
- 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.
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.
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.