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.
