Pulverizing Asphalt Pavement

[Roadwork]

Anyone have experience with mix-in-place asphalt pavement recycling? Does it work well? Do you recommend it? Any pitfalls to look out for?

Also, is an injected emulsion additive necessary, or can this be done dry with water mixed in to get proper compaction?

I'm considering using it on a 2 mile section of secondary roadway (low volume), that has structurally failed. What about the pulverizing process itself? Does it cause alot of ground vibration, or is it more of a slow grinding process? (We have alot of work shops adjacent to this road, so ground vibration, may be a problem).

 

[ACtrafficengr]

It can be very effective, but make sure you get a contractor that knows what they are doing.

You can just mill asphalt, or you can go deeper and mix in some of the underlying base course. The latter can be useful if you have excessive fines in your base, and that caused the pavement failure. Mixing the ground asphalt particles in with the base course effectively reduces the fine content for the depth you mill.

You can compact the millings as is into a granular base, and put a complete HMA base, binder and top coarse on it, or you can inject one of various stabilizers into it. Asphalt emulsion, portland cement CaCl (actually more of a compaction agent than a stabilizer) or foamed asphalt are commonly used, depending on the need.

Foamed asphalt uses hot (>100 deg C) liquid asphalt and water. The water expands in to steam, foaming the asphalt and helping it coat the particles better.

Cement will work at higher %fines than asphalt, but if you use too much, you will get shrinkage cracks in your subbase that will reflect up through the new top course. You don't need much - the resultant concrete stabilized base course has a strength of ~500 psi.

Unless the workshops are doing work of extraordinarily sensitive nature, I don't think you need to wrry about the vibration. Vibratory rollers are almost as loud as the grinder. Recording studios might want to stop recording when the recycling train is within a few hundred feet, etc.

If this is for a public highway project in the USA, you might want to call your state's LTAP center (

http://www.ltap.org).

They will have resources to help you.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[Roadwork]

Is the machine used for grinding a milling machine, or something else?

The reason for the failure is that the road is just old (20 + years), and was not very well maintained. I haven't had any boring done yet, but I'm told (by one of our long-timers) it was originally a macadam road, and it looks like about 4"-6" of asphalt on top of that. Seems like a good situation for recycling. I'm thinking of mixing the full depth of the asphalt and macadam (probably about 8"-10") to create a good base course, and then paving on top of that. For this case, cement as stabilizer would probably be the best choice, due to the heavy macadam presence. Would you agree with that?

Also, would you know where can I get some sample specs? Know of any DOTs that use this process on a regular basis, and have specs available online?

 

[ACtrafficengr]

As you can tell by my screen name, I'm not a pavement maven. I'd better just say you need to get core samples and verify what you are dealing with, and talk to a pavement expert. Try your state's materials or construction bureaus, and your state LTAP center.

"Old Age" isn't a recognized form of asphalt distress. There are various kinds of cracking, rutting, disintegration (ravelling, etc), bleeding, delamination, but not old age. Proper identification of the distress type is key to choosing the proper treatment.

Millers can be used, but if you are going full depth, you might want to get a grinder. It looks like a scraper, but instead of the belly pan, it has a huge grinding wheel, as well as injectors for your emulsion, cement slurry, or whatever you are using.

Good luck!

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[Roadwork]

I agree old age isn't a form of distress, that's why I stated it was part of the "reason" for the failure, along with lack of proper maintenance, not the characterization of the failure itself.

But thanks for your help. I am really just trying to get some further insight on the pulverizing/recycling process itself. Thanks.