OT-- Questions About Blacktop

A couple of months ago we had a very informative thread about sealing blctop; I hope some of those who answered are still around and can answer some questions about overcoating an existing drive with another layer of blacktop.

The existing drive is likely over thirty years old, but not in terrible shape, however the 13’ wide pavement has “panelized” into sections from 15’ to 20’ long from shrinkage. In addition, the last twenty five feet before the garage needs to be removed because; it has been trenched through for a new line from the well (4’ deep, backfilled with sand toped with stone two years ago) and again for a new underground electric service (2’ deep, 6” wide, backfilled with existing excavated stone, last year). The few remaining patches of pavement need to be removed to meet the grade of the existing concrete sidewalks and garage apron, anyway. I am confident that the backfilled trenches have settled to full compaction since they’ve gone through all the freeze-thaw cycles of one and two winters.

One contractor wants to dig the entire drive out, all 2800 sq. ft.; says it will crack where the old cracks are. That is undoubtedly true, but what’s to keep the new drive from cracking? It seems a waste to dig out what amounts to 2” of solid stone fill, disturb the sub grade, then have to smooth and roll it back flat before putting new pavement in.

What about the crack bridging fabric the state highway departments use? Is it any good? One contractor is willing to write a price using this, but I don’t have it yet.

One contractor flatly refuses to price the fabric. Their solution is to grind the cracks wider, patch them with blacktop, then go another 2” over all. Somehow, I fail to see how doubling the number of non adhered joints in the sub grade will prevent the new layer from panelizing, but hey, what do I know? One thing that puts me off about this last contractor is their quote includes an additional charge for a “required” application of sealer, appx. one month after the paving is done. Everything I’ve read says you do not want to seal new blacktop for at least a year after it is applied, or the surface will remain soft from solvents trapped in the pavement.

My only experience with purchasing blacktop paving was a commercial lot I had done ten or so years ago. The existing was chip and seal over a good stone base, but the pavement had panelized into pieces the size of dinner plates. I heard all the same arguments about digging it out, but the budget wouldn’t allow it, so I just told the guy, “I don’t care, pave over it.” Now that it’s been in for ten years, it is getting shrinkage cracks between the strips it was laid in, but the random cracks have not yet propagated through.

So, what do the experts say? Which would be the best course for first cost vs. durability?

Dennis

Not any expert, but have heard good things about the use of engineered fabrics. Have also heard there's a lot of resistance to their use, based more on pavers doing what they know than actual experience with the fabric. Given the cost of oil today you're surely on the right track to be asking.

If the fabric being discussed is similar to what I know as geofabric it is intended to stabilise soft ground before compacted roadbase is placed. The geofabric assists with the drainage of wet areas. I can't see any advantage in this situation. I would be still concerned about the compaction in those trenches. I would opt for starting again with extra compacted roadbase then bitumen seal.

Damien,

The use of geotextiles under the stone road base is intended to keep the stone from pressing into the ground below, or the loose soil from infiltrating upward into the stone base, clogging drainage. It's common here these days in railroad construction, where high cyclical loads on the track cause a pumping action that liquefies the waterlogged soil below and forces it up into the stone base.

But they also use similar textiles between layers of pavement. In this area we have a lot of two lane highways that originally had sixteen foot (5m) wide concrete pavement, to which strips first two feet, and later four feet were added outside the edges to meet later standards for wider traffic lanes. These longitudinal joints are a real pain, as they always propagate through succeeding layers of blacktop pavement, and the crack is always right where one set of tires runs in the wider lane. The application of the fabric bonded to the existing road surface seems to prevent or delay this crack propagation. What I can't find any hard data on is whether they intend this to be a reinforcement for the new layer, or whether the intent is to establish a shear plane, so that the new layer can expand and contract somewhat independently of the separate panels of pavement below. It seems to work on the highways; although the paving contractors who don't want to use it say it doesn't, and I can't find any data that would indicate it's cost effectiveness vs. a complete tear-out.

I'm not worried about the trench backfill. The best way to backfill a trench is in layers of 6" or so, using a material that's easy to compact, such as sand, and mechanicallycompacting each layer before the next is applied. The next best way, where the cost of labor and machinery to compact fill in layers can't be justified, is to use a material that compacts easily, such as sand, and let water perk down through it, rearranging the grains into a more compact mass as it passes. That's the method I chose, putting a layer of crushed stone on top so vehicle tires didn't continually disturb the sand, but thin enough that it couldn't lock up and bridge over any voids underneath. The fill in the trench has indeed settled over time, to which I've added more stone to maintain a flat driving surface. I haven't seen any evidence of further subsidence of the larger trench during the second winter, which tells me that all the voids are gone and the backfill is now at near 100% compaction. The smaller trench for the electric service should be reaching that point now, but I'm not waiting another year to watch it. My wife is tired of having the sand fill bring rainwater right to the bottom of the foundation wall and cause seepage in the basement; I need to get some pavement down to shed the water away from the building.

Dennis

Modelman

Paving fabric is as you say to try to stop joint transfer between the layers. I have some experience with it as an inspector but not in field use. We used it in an overlay for a parking lot and it seemed to keep the cracks down for a number of years. They did come through but by then we has other issues with lot.

From what I understand, most pavers do not like it because they have to be careful when they move over the fabric. It has a tendency to stick to the paver tires or track (not to mention the trucks) and pulls up. Most of the uses I have seen with it, they have used and 18-inch strip so if it slips a little, it will still cover the crack. The biggest issue is that cracks do not run strait and what may seem excessive at a particular spot is not when looking down a run of it.

You never say, but what do you plan to do with the existing if you leave it in place. How much overlay? My suggestion is to think of rubalize in place and then place mix over this. This will allow water to go down if it gets between the layers and not freeze between them and blow the surface up.

The biggest issue with an overlay is how much it changes the grade and drainage of the area. It may cause water to stand in places and worse, more water to run into the garage or house foundation. A good contractor will not damage the sub-grade when removing the existing asphalt.

Without seeing the site, my first recommendation is to rubalize in place and overlay it to the surface. This way you get the benefit of the stone and make filling and leveling easy.

Hope this helps

Roger

rsal said:

...You never say, but what do you plan to do with the existing if you leave it in place. How much overlay? My suggestion is to think of rubalize in place and then place mix over this. This will allow water to go down if it gets between the layers and not freeze between them and blow the surface up.

The biggest issue with an overlay is how much it changes the grade and drainage of the area. It may cause water to stand in places and worse, more water to run into the garage or house foundation. A good contractor will not damage the sub-grade when removing the existing asphalt...

Without seeing the site, my first recommendation is to rubalize in place and overlay it to the surface. This way you get the benefit of the stone and make filling and leveling easy.

Hope this helps

Click to expand...

Roger,

Thanks for the comments. I had given some thought to the fact that if one ran a "sheepsfoot" compactor over the existing pavement, that would indeed eliminate the present panalization as a factor. None of the contractors have suggested it; I suspect none have that piece of equipment at their disposal.

Everyone is talking 2" of overlay. There is only two inches there over the stone base now, and that's all any of the contractors intend to put in new, unless I insist on (and of course pay for) more. This is, after all, a residential drive. Then again, even residential drives see occasional heavy loads; the well drilling rig came in on that pavement, and the electric company brought their pole auger truck all the way up it. Garbage trucks aren't light, and neither is the septic guy's truck. None of them ever put ruts in the existing pavement, thankfully, but I'm sure they all contributed to stress cracking.

So that's the dilemma. The existing pavement isn't a collection of loose chunks rolling around, so it obviously still has the ability to spread point loads, and since I already own it, I'd like to keep it. On the other hand, since it has cracked into panels, the overlay most certainly will too. But then again, I can't see a 2" thick sheet of pavement 120' long not eventually shrinking and cracking all on it's own, just as the original did. Everyone wants to dig the existing out, for which they will charge me, so it doesn't cause the new pavement to crack into panels, but the new pavement will crack into panels anyway. Kind of makes me wonder if I shouldn't just tell them to pave over what's there and save the dig out money. I do realize that the existing needs to get a coat of liquid asphalt to bind the new layer to it.

Changing the grade isn't the problem; everyplace where the new pavement has to meet existing grade, the garage door apron and a couple sidewalks, is back in the area that's been all torn up by trenching for the utilities, so it's a foregone conclusion that this portion has to come out so the new pavement can be at the proper elevation. The only difference between my little corner of Illinois and a pool table is my yard doesn't have side pockets. Luckily, the builder had the good sense to raise the grade around the house about 2', and the existing drive drains well. Adding two inches to it isn't going to change anything appreciably.

It's getting to be about time for some quotes to come in. It should be interesting to see how the different options price out.


Dennis

Dennis:

The sheepsfoot is not a bad idea. Would work real well but as good a way is a drop hammer but a heavy vibratory roller and a few hours can break the panels up. I was concerned that you would go less than 2-inches as it would have been better to glue the dollar bills down. Thin overlays always crack. If you do fracture the panels, tack is not needed (depends on the size of the pieces) Do realize that they charge to remove the old and that is where they get the most of the profit (they develop the attitude that once is covered, they can not see things anyway so who knows what was done to the sub-grade) because the asphalt costs are mostly fixed due to material and oil. There is not much leeway on this as there are only so many suppliers and competition rules the market. Get a breakdown of costs they propose and then calculate the square footage and convert to square yards and multiply this by 220 and that will give you the tonnage they should use. You can always call an asphalt supplier and ask what it is selling for a ton with a set quantity (this just happens to be the amount you need plus a ton or so) This lets you compare apples to apples. You do need to add the haul bill in somewhere (fuel you know)

One thing to consider is the mix design. Around here we can get something called "over sanded binder" It sort of gives the strength of intermediate (binder) with the sealing qualities of surface. The draw back is it looks a little rougher but it is not that bad. Not real open but not closed up like surface. Does not get as slick in the winter as surface but some people do not like the look of it as they consider it unfinished.

As long as you are meet the important things and do not cause yourself a drainage issue, I say do what you want. Remind the pavers that you are the owner and if they do not like it, hit the highway. There are other paving companies around.

If it was mine (I would rather have gravel as we have the machinery to fix it and the occasional load of stone is not much.... before the fuel surcharges that is) I would remove what is needed to meet the garage and other important items, lay a small wedge taper to the grade of the existing drive and pave over it. If I could find a drop hammer or small mounted air or hydraulic hammer (bobcat with a demo hammer is great for this), I would break it up, if not I would not worry about it. Neat thing about asphalt being classified a flexible pavement is that it does bend when stressed but always breaks or cracks due to the stress. Cracks are going to happen unless you remove all of the old and then it is not a guarantee. (unless you keep it inside on a surface plate in a constant environment and do not subject to stress, but then the ozone attacks it so no guarantees.

I would go so far as telling them they are to lay the asphalt and if I am happy with it at the end, smooth surface, lack of roller marks, they do not pave your mailbox over, ect..... I would not expect them to be responsible if it cracks (after they proved the mix manufacture and provided the mix design and copies of tickets as this will cut out the fly by night guys) I would go so far as putting it in writing to them.

Bottom line, your drive, your money, they can please you or someone else will.

Riger

I just had a "go around" with my driveway. It is 18 years old and a bit tired in spots. One major crack across the driveway directly over the culvert. That is incurable, (the paving man said so, but I recognized that there is simply not enough cover over the culvert because of the slope.) I suggested having the driveway torn up and replaced. My paver was outraged! I apparently have a medium aggregate grade and it would be replaced with a fine aggregate because in this area that is what "everyone" is using. Aside from $4500.00 he said it would not last as well as what I had. He ended up repairing a couple of spots with the rolled fine stuff and sealed the whole driveway, (about 18'x75') with a naphtha cut tar product. The important point is that the asphalt plant is not going to run a few truckloads of a custom blend. You are pretty much at their mercy, but if you have any druthers, get a fairly coarse aggregate mix. After all, its proper name is "asphaltic concrete" and like any concrete, the coarser the aggregate, the higher the strength and durability but the less beautiful. Duffy

rsal said:

... and they do not pave your mailbox over, ect....

Click to expand...

LOL Reminds me of years ago when I was involved in moving a railroad car body off a summer cottage lot, high centered the truck on the road and had to call a wrecker. There were a bunch of mailboxes in the way of getting the wrecker in, like all the mailboxes for the whole lakeside community. So, we wiggled them around and pulled them out; put them back when we were past them, but apparently not in the same order. It was most interesting to watch when people arriving home went to check their mailbox…


The quotes are starting to come in via mail, and it's obvious what Roger says is true, removing the old pavement is a profit center for these guys. I hate when people ask questions on these forums, then disappear, so when all the quotes are in I'll share both the prices and what the contractor says he'll do for his price. Maybe it will help someone else make an informed decision.

More later.

[FONT=&quot]Dennis[/FONT]

Even the state QA HMA mixes will crack eventually in an overlay. Additionally, because of the freeze thaw cycle you have in IL, the expansion/contraction will lead to cracking. If your existing asphalt is "alligatored" into sizes smaller than a typical pizza, I doubt anyone would overlay it and give you a guarantee. I don't know what the native soil is like where you live, but with respect to the "trench backfill" true, it will settle out slightly over a 2-5 year pattern if it is initially compacted to say 95% of it's theoretical maxumum density. The amount of settlement would be a function of the intitial compaction and the depth of the trench. Additionally if it is markedly different than the native soil, say crushed sand backfill vs clay, it will react to freezing and thawing differently. Also, granular material will typically retain more moisture than a cohesive material like virgin clay. Being a sewer/excavating contractor since 1989, I deal with this all the time. Hope this helps

Time to bump this up to the top, since the quotes are in.

Wow, I missed seeing this last reply. The existing pavement isn't alligatored; it is simply broken into panels between 15' and 20' long. The one exception is where there is a pre-historic pipe trench that runs under the drive (that likely dates to the construction of the house in the fifties) which has cracked with several parallel cracks in the direction of the run of the trench, which has settled an inch or two. And that points out the problem with trench backfill; the underlying soil is blue clay, and without compaction, it settles for decades. Compaction is easy when the whole width of the roadway is involved; just spread in 6" to 12" layers and run the sheepsfoot back and forth over it. In a trench, it is well neigh impossible to obtain good compaction with clay, which is why sand is commonly used around here. Years ago I worked on an Air National Guard hanger, and that's what was the specified for backfill around the foundation walls; all sand from undisturbed earth to pavement grade. If it's good enough for the Corps of Engineers, it's probably good enough for my house.

I've received four quotes. No one is offering any guarantee longer than one year, which is ludicrous. As Roger predicted, excavating seems to be a profit center for these guys. The job is appx 2400 sq. ft., of which about 600 have to come out for sure in order to meet existing grade at garage and house sidewalks. There is Appx. 16' of saw cut or milling required so the new pavement will meet the existing street (no concrete curb.) Each firm's estimator did his own measurement, and each was asked about "fabric" for crack suppression. Here's the results:

1)Completely remove old pavement, re-grade and compact base, saw cut street, apply 2.5" of "surface mix", tamp edges and roll with vibratory roller. $8,375

2)Completely remove old pavement, re-grade and compact base, saw cut street, apply 2.5" of "surface mix", tamp edges and roll with vibratory roller. $6,530

3)Remove 375 sq. ft. and re-grade, pave with 3"; saw cut or grind butt joint at street; overlay existing with 2". Even though we discussed grinding out the cracks there is no mention of this, or the tack coat, in the quote. This firm also figured the job 400 sq. ft. more than the others, , but this may be to account for the thicker application by the garage.
$5,889, plus $505 for "first time seal coating."

4)Saw cat at street; clean, prime, and level existing surface; install petro-mat; install 2.5" hot mix surface asphalt overlay; tamp all edges. $4,750

This last was the only guy who would quote Petro-mat; see:

http://www.ind-fab.com/petromat.php
http://www.ind-fab.com/downloads/petromat-install.pdf

They must be familiar with the material because they have a check-off box on their proposal for it. He also hedged his bet by noting, "deduct $650 if no Petro-mat" so $4,100 must represent the actual cost of the paving the area, with the additional three or four grand for excavating. Since no one is offering a guarantee anywhere near the expected life of the pavement, I'm inclined to go with the fabric and better price. Time will tell if it's the right decision or not.

Thanks to everyone for their comments.

[FONT=&quot]Dennis[/FONT]

Dennis -- I hope you'll give us a 1-2-3 year report on how the fabric works for you. Sure could save a lot of us trouble and money if it works.

Dennis

I would watch the one with the overage of square footage. It is a common trick here to pad the area to cover any overage they may run into and pad the profit some. It would be better if they specified the tons as that is easier to compare. It is unusual to get that much difference, I can see about 100 sf or so but even then the difference is not normal.

A quick check of the footage you gave would show about 40 ton to be used (take the square footage and convert to square yards. Then use 110lb/syd per inch of thickness) I did use 120 as it seems to be a better estimator than the 110. Based on the last number I heard ($67/ton) it seems that there is about 2700 in the mix. The remainder would be haul bill and the like.

If #4 is going to remove the 600 or so that you know needs to be removed and meet all of the walks and garage and street. It is by far the best price but what about the quality of their work? Ask for references and contact them. You want to look at jobs that are a few years old to see what they look like.

I am like you, I would lean to #4 with the petro mat. I do know that petro mat is dependent on proper installation so you may want to ask how many times they have installed it. In the end, go with the one you are most comfortable with and has a good reputation. Most poor pavers do not stay in place or business long nor want to give any names of past customers out.

roger

Pardon, this may be the longest interval thread bump ever. I just searched for this thread as it was the quickest way I could think of to establish when I had my driveway re-paved, and I had forgotten that PeteM had asked for 1, 2, 1nd 3 year follow-up reports. I think PeteM is still reading, so here goes.

There was really nothing to report the first three years, the drive was just smooth and black. Years four through ten it got progressively lighter in color, but no cracks. This year I can see a few cracks across the drive which will break it into panels. As of this point they have neither misaligned or opened. I can't really tell if they are in the same locations as the cracks in the previous layer of pavement, but I'd say the crack suppression fabric was worth the money. This is the first year I'm looking into having the pavement sealed. Now that I can see cracks, there is something to keep the water out of.

The area where the original pavement was removed to meet existing concrete work hasn't fared as well; the surface has some interesting dips and wallows, which are the result, I'm sure, of the pipe trenches discussed earlier in this thread. There is spider cracking over the largest of these trenches. I'll have it sealed for now; at some point it will make sense to take out that 600 sq. ft. or so and have it replaced, but not until the trench back fill has a few more years to settle.

Dennis

Appreciate the follow up, Dennis. Thanks -- this will help many of us.