Asphalt Crack Repair 1

[concretebaby]

Dear All,

We have a concrete deck paved with asphalt wearing course 50mm thick. There is a 4mm thick waterproofing membrane between the concrete deck and the BWC. Due to the debonding effects and low compaction, some of the paved areas are cracked.

What is the best solution to fix-up these cracks? Whether to cut the 50mm asphalt and putback the membrane and re-lay the asphalt or to fill these cracks with a bituminous grout?

The crack width is 2mm approx.

Please help...

 

[Ron]

Use hot, rubberized asphalt sealer for pavements. Clean the cracks with air, then place the sealer in the cracks with an application wand.

 

[concretebaby]

what is application wand? what specs does rubberized asphalt sealer conforms to? pls specify

 

[Ron]

The ASTM standard that applies to this is ASTM D6690-Standard Specification for Joint and Crack Sealants, Hot Applied, for Concrete and Asphalt Pavements

An application wand is a metal tube attached to the end of a flexible tube that receives the melted, rubberized asphalt sealant from the heating kettle. Most of the kettles are small and hold from 50 to 100 lbs of sealant at a time. The wand is used to deposit the sealant directly into the crack.

 

[Drumchaser]

Would the "concrete deck" be a bridge deck? And if so, an overlay on a bridge deck with insufficient "membrane" can sweat and cause debonding.

Of course depending on the particulars... (how much surface area you are describing)..and how much the budget is...sight unseen I would recommend removing the wearing course, placing a two course chip seal, relay the ACP, with a much improved product. Who is to say the crack-seal option would not have to be repeated in the short term.

 

[concretebaby]

I have found rubberised cold applied bituminous sealer. Will this be a better option than hot-applied sealer?

Two course chip seal? pls elaborate. We have asphalt design mix with 3/4'' (10%), 3/8'' (35%), crushed sand (40%), filler (5%).

What will be the most durable solution for this problem??

Anyone....

 

[Ron]

cold applied sealers are emulsions and tend to shrink a little as they cure, though they are still effective. Hot applied sealants are more durable and provide a good bond to the asphalt.

A chip seal is a hot asphalt flood coat applied to the pavement then graded gravel is placed into the hot coat and rolled to create a covering for the underlying asphalt. In the process it will fill a lot of cracks and provide a new wearing surface for the asphalt; however, it will have a rough texture. Doing this process twice creates a double chip seal.

For chip seals, the aggregate has a greater potential to become dislodged under heavy or high speed traffic and you might get more complaints of vehicle damage from "flying gravel". It's a good process and works well, just be aware of that issue.

 

[ACtrafficengr]

Drumchaser, do you mean relay the ACP over the chip seal, or as an alternative?

I know there is no way to answer without knowing the cause an extent of the cracking, but would a chipseal or other surface treatment over the existing wearing course be an option?

Just to make sure, Farhanjn, have you checked the condition of the underlaying deck? We just had to close a bridge because the cracks in the wearing surface were due to problems in the concrete.

"...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

 

[concretebaby]

I would come back again on this,

1. The structures affected are Piers and Wharves. Resting on series of vertical and raker precast piles, precast beams and deck planks, we have in-situ concrete deck 180mm avg thickness.
2. There lies above the concrete deck, a 4mm thick hot-applied waterproofing membrane.
3. Above all an 50mm avg thickness asphalt wearing course has been layed and compacted.

Reasons for cracks:

1. Debonding between deck-membrane-bwc because of improper application of membrane resulting in air-pockets above the deck surface. As the air entrapped in the membrane increases/decreases due to temperature changes, the asphalt expands and cracks on the top. There are soft spots at various locations and can be pressed by foot.

2. Lesser thicknesses of bwc at the ends of the structure in order to provide slopes. (upto 30mm thickness have been observed at some areas)

3. Low compaction and drop in bwc temperature during paving.

Most of the cracks have developed in a series of interconneced circular mode. Min width= 1mm Max width = 3mm.

The concrete beneath is crack free, sound, dense with a compressive strengths upto 60 MPa, tested and approved.


We have tried to apply cold elastomeric rubberrised sealer, but the setting times and patches created are too high.

Please throw some light on the above and some detail on the best repair option...

 

[Ron]

farhanjn...you have a few choices.

1. You can use a hot applied crack sealer as previously suggested. This will work to seal the cracks but won't solve the overall problem of debonding.

2. You can do a sand-slurry seal (similar to chip seal, but using sand rather than coarse aggregate). Advantage is that the top surface will be smoother (still won't solve the debonding problem)

3. Mill the existing asphalt, fix the debonding membrane, and place new asphalt wearing course. Best option, but most expensive.

 

[Drumchaser]

AC-

Sorry if I was not clear.

Yes:
1) Remove the asphaltic concrete pavement.

2) Place a (TwoCourseSurfaceTreatment) 2 course chip seal [one directly on top of the other].

3) Replace the asphaltic concrete pavement.

This has been SOP in my area for a very long time. The bridge slab has a tendancy to sweat (btw. the top of concrete and the ACP) causing a multitude of problems if the chip seals are not present.
Moisture barrier.


Farhanjn-
Sounds like your new wearing course was placed to cold and is now "checking"...mill it off and start over if you can.
With a moisture barrier of course.

One other thought...depending on your material(s) used as a waterproofing membrane...it is common to have a "cure period" before placing ACP over the top...sometimes without enough cure time there are problems with the ACP and the membrane.

A picture would say a thousand words.

Ron-

Yes. "flying gravel" is always a possibility, until you get it covered up (w/ACP).