Repair asphalt with concrete patch 1

[drewnje]

I don't work with asphalt pavement often; however, we have a client in need of some repairs to the asphalt pavement around their facility. The combination of heavy trucks, vehicle braking, and repetitive turning (and possibly improper drainage) has created some cracking, rutting, and shoving in the asphalt. Although many, the areas area localized and are relatively small. My initial thought is to cut out the failing sections of asphalt, prepare/compact a suitable subbase, and replace the asphalt with concrete pavement. That said is there any thing I need to take into consideration when doing this or is it as simple as I make it sound? Are any additional measures required at the transition from asphalt to concrete? Any advice or any direction to related literature would be greatly appreciated.

Thanks!

 

[Ron]

Not a good idea.
Concrete patches will shrink away from the asphalt, allowing surface water to get into the crack between the two different materials and you'll have same problem all over again.

If you are experiencing rutting and cracking, your pavement section is probably nearing the end of its useful life, particularly if the use is for trucks.

If you must patch the isolated areas, cut a proper area of asphalt out, exposing the base. Repair the base with material similar to what is in place to prevent "hard spots" or "soft spots" in the pavement that will show up later. After the base is repaired, apply a proper asphalt patch.

If you have a lot of small cracks, you might consider an asphalt slurry seal over the entire pavement to give you a little protection for the base and give your owner time to plan and budget a pavement replacement or overlay.

 

[drewnje]

Ron, in one area the client requested the concrete. It's an area approximately 50' wide by 30' long approaching two truck scales. There is some severe shoving in the asphalt as trucks brake before entering the scales. How would concrete here be any different than a concrete dumpster pad in an asphalt parking lot?

No doubt the asphalt is near the end of its life. The client; however, does not want to spend the money to replace it. They would rather just put a band-aid on it as needed.

 

[hokie66]

drewnje,
I think Ron was talking about "patches" a lot smaller than that. For the use you described, I think a rigid pavement is the solution. He is correct in that the edges will be susceptible to surface water infiltration, but that can be addressed by maintenance sealing.

 

[drewnje]

I should have been more clear on the size. The smallest area is a rectangular area that is 5' wide by 20' long.

 

[drewnje]

Hokie, what do you recommend for sealing the edges?

 

[hokie66]

I would look at a bituminous sealant. Try Sika or another big sealant company for recommendations. Make sure you tell them it is for old asphalt to new concrete.

 

[Ron]

Sorry...As hokie66 noted, I was thinking about a small patch. I agree that a rigid pavement section would be appropriate for what you later described. The transition between asphalt and concrete must be sealed and maintained. Many years ago I designed a transition between asphalt and concrete that has served well. The concrete face at the interface between asphalt and concrete is sloped so that when traffic goes from asphalt to concrete, it actually pushes that asphalt harder against the concrete, thus helping to maintain the seal.

Attached is a detail of this concept. It requires supplementing with appropriate specifications for priming the concrete, sealants and other job-specific criteria, but you'll get the idea from it.

Good luck.

 

[DDBPE]

Do not use concrete for an asphalt patch. As Ron stated, you will have separation at the joints, one is flexible the other is rigid

Do you know the cross section? If you have a multiple lift asphalt section I would repair the areas as follows.
1) Saw cut and remove the failed asphalt (keep it square or rectangle if you can)
2) Evaluate the base (if it is wet, you may have a subsurface condition to deal with)
3) Re-compact or replace the base material if needed.
4) Tack all the edges and replace the base layer asphalt up to the bottom of the surface layer.
5) Mill 1'-2' beyond the edge previously saw cut 1.5"-2" depth (to remove the surface layer only)
6) Tack all surfaces
7) Replace the surface asphalt.

One key to asphalt patches it to prevent a continuous joint from the surface to the base material (unless you only have one lift of asphalt).
By milling the surface area wider than it was saw cut, the joints will be staggered. Also, if you can, patch the entire lane width versus patching only one wheel path, likely the wheel path not patched will fail next and it is easier to pave back with an asphalt paver and rollers (typical pavers are 8'wide)

The scale approaches should be concrete, most companies that certify scales for states will not certify a scale if the approaches are asphalt we had to change ours out a few years ago because of this requirement). The typical transition bump created by the failing asphalt affects the scale. There must be a smooth transition from the riding surface to the scale and from the scale back to the riding surface to prevent damage.

For the asphalt to concrete transition, sealing the surface as hokie66 is a must. After the concrete is placed, typically, the joint is sawed to around 3/8" wide to a depth of around 2-3", backer rod installed, and sealant placed. Most manufactures have a detail for this.

 

[Twinkie]

Can the subgrade support the concrete? If you are having such issues with asphalt, the concrete may crumble

 

[Ron]

Twinkie..concrete can generally be use on subgrades that are less competent than those for asphalt. This pavement has been performing with asphalt and would certainly do so with an appropriately designed rigid pavement.

 

[tubsdua]

Dear drewnje,

We have a similar situation in one of our works. We are maintaining a busy runway in India and there is a time constraint involved in the repair/maintenance activities here. The overlay of flexible runway is now 10 years old and defects like raveling, alligator cracks and pot holes are very prominent. We have tried asphatic concrete patch work, epoxy patch work and polymer emulsions. So far only polymer based emulsions have proved to be the best option. In places where pot holes are existing the emulsion is mixed with sand and 10 mm aggregates and applied. The setting time is hours so the traffic can resume immediately. Although we are using Indian brands I am sure companies like SIKA, FOSROC, BASF are manufacturing such chemicals. You can also try the following link which by the read of it sounds good.

http://www.geocheminc.com/percol1.htm

We would be happy of you post your feedback on the same back here for us to gain from it. Specifically the brand of chemical and its performance. Looking forward

Cheers,
Alok

 

[oldestguy]

Not all areas have a ready supply of hot mix that duplicates the usual roadway asphaltic concrete mix. You may have to go to a cold mix that is an emulsified asphalt instead of the usual heated asphalt in the mix. That can sit in a pile a long time before being used. Usually only for small area patches however. It may be too soft for immediate application of traffic also.

 

[chicopee]

On interstate I91 around the City of Springfield, MA there is a whole bunch of concrete patches on the elevated asphalt pavement. This has been done for a number of years with no known problems of course the prep work is extensive but the results seem satisfying.

 

[beej67]

Pink star for Ron. Chamfering the interface is a neat idea.

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