Expansion joint seal to resist snow-ploughed ramp 1

[ajk1]

The following questions are addressed in particular to structural engineers who have had extensive experience in parking garage design, in Canada or the snow belt areas of the U.S. (or anywhere else in the world). I have many decades of experience with parking structure design but am still looking for an expansion joint seal system that has a proven record of watertightness (say for 10 years minimum) and resisting snow plough damage. Cost should not exceed $1000 per metre. ($300 per foot). There is no use saying to use a rubber blade on the plough, or to raise the blade a little, as that will leave a layer of snow/ice on the surface which our clients tell us is unacceptable for liability reasons. Also turning the blade at an angle to the direction of travel is something that is hard to enforce when an outside contractor is doing the ploughing.

Questions

1. What is the best expansion joint seal to use to replace an existing seal in an existing 60 foot wide ramp that is snow ploughed in the winter? The existing joint is 1" wide. The 60 foot length of the joint is at right angles to the direction of traffic.

2. Sometimes a Wabocrete type joint with elastomeric headers is used and paved over with asphalt. I know that this results in the asphalt cracking, but it may (or may not) nevertheless be the best way to protect the seal from damage if one is prepared to deal with the asphalt cracking. Does anyone have a detail of this?

 

[Ron]

Have you tried a duplex joint system where the upper joint seal is sacrificial and the lower seal provides the primary sealing?

 

[ajk1]

Ron: I was actually thinking of doing that, although I don't think I have done it before. What would you use for the upper (exposed) seal of the duplex system? It would still have to resist snow plough damage.

 

[oldestguy]

While I am not involved with expansion joints, but do deal with maintenance of paving. I have noted that when asphalt paving cracks are routed out and a hot rubberized seal is poured in, usually best done in spring of the year, that they do not get ripped out by snow plowing. Apparently the stretched material stays low enough and is sufficiently bonded to the paving mat to resist any such action. The width of the routed cracks sometimes is about an inch plus or minus. A rare rip-out has happened if the joint filler is done on non-routed cracks and sits too high.

 

[bridgebuster]

Snow plows ripping out joints seals from parking lot decks is no different from ripping out seals from bridge decks. Attached is a chart from the D.S. Brown Company that compares the service life of various joint systems. Personally, for a 1" joint I would use a backer rod and pourable sealant; keep the top of the sealant 1/8" to 1/2" below top of deck. It's a simple installation; almost idiot proof. I have nothing against elastomeric seals or closed-cell foam but they take a sometimes bit of work to get them to sit properly. Sometimes the wrong size is installed and as a result they pop up in the summer or fall out in the winter.

Are you replacing the joint headers? Elastomeric concrete headers are fine but not all elastomeric concretes are created equal. Urethane-based elastomeric concrete is top of the line but a contractor isn't going to use it unless required to do so. There have been a lot of problems in NY with elastomeric headers, mainly debonding from the concrete substrate. I've seen premature header failures on newly constructed bridge decks that don't carry truck traffic; the ones I've seen are the non-urethanes. Whether it's the material and/or the installation is unknown because there hasn't been any significant research. Now we're trying different things to prevent debonding &cracking.

If you're putting in elastomeric headers consider doweling in No. 4 bars with 90-degree hooks every 8" along the joint, with 3" of cover . I lean towards no longitudinal bars; some people add two per header. Nearly 30 years ago where we were putting in headers using the old Set-45, the plans called for longitudinal bars. Some headers cracked prematurely and it was determined that the failures were due to the material not fully encapsulating the bar in some spots. As a result of the traffic vibrations the bar would vibrate and crack the header. That always sticks in my mind with these exotic rapid set concrete.

 

[ajk1]

Thank you for the information.
My experience with a backer rod and pourable sealant has been quite different from yours. They fail in both cohesion or adhesion, they do not have the required elastic elongation properties to accommodate the movement at expansion joints in exposed parking garage floors in our climate (Canada) that undergo large thermal movement, they cannot make a proper upturned transition at walls/balustrades at the ends of the joint, and so on. I wish it were not thus, because that would make the solution easy and cheap. That may be why there be a market for $100 to $300 per foot proprietary parking garage expansion joint seals that have found wide acceptance. I know of no parking garage built in the last 30 years in my area (Ontario) that uses a backer rod and sealant as you describe, although some older garages did use that, although it was usually a looped butyl sheet. Please forgive me if I have come on too strong, I do not mean to.

Thanks again for taking the time to respond. Much appreciated. if there are any more thoughts I would be interested in them.

My opinion is that there is no expansion joint seal that will stand up to snow plough blade damage, and paving over the seal will result in ugly cracking the asphalt.

 

[Canuck65]

ajk1,

If you want to look through some manufacturer's information, I would direct you towards the MTO list of approved expansion joints for bridge decks. Under the structural section 9.40, you will find the list for expansion joints. There is a wide variety, unfortunately based upon our experience, they likely will not fit your budget. Perhaps you would need double your budget, $2,000/m. However, they do stand up to snow plow damage very well. We tend towards Type A as being cheaper, however, Type C are typically easier to replace the seals on, during future maintenance. Perhaps if you contact some of these manufacturer's who are used to doing business in Ontario, they might have a 'light' version that would be suitable for your application. Please note that after you click on the type of joint and the list of manufacturer's comes up, there are also clickable links to the standard MTO drawings related to each.

http://applications.roadauthority.com/mpl/mpl.asp?MPIShortName=MTO+DSM

 

[bridgebuster]

ajk1 - no problem if you don't like pourable seals. All of us have different experiences and biases. What type of joint system is there now and how does it fail, is the plow ripping out the seal?

 

[ajk1]

To Canuck65 (Structural)- thank you very much for this. Sounds like it is right on topic, although beyond what our clients would generally be willing to pay, but good to know that there is something that works even with snow ploughs. I will find time to study it over the next day and get back to you if I have any questions. Thanks again so much.

To bridgebuster (Civil)- the type I would like to use as seemingly to have the properties I would expect to be necessary to resist snowplough damage is the one with steel side rails set in elastomeric concrete headers, but the problem is that I have seen that the snowplough blade can distort the steel rail and then it leaks. I have not seen actual "ripping out" of any of the joint seals.

The worst thing I have seen is where a steel cover plate is used to protect the joint gland. That I have seen ripped out. It is very difficult to properly anchor a steel cover plate with fasteners down thru 2" minimum of asphalt into the concrete because any horizontal force at the top of the anchor will put a moment on the anchor. I would not use steel cover plates.

I designed 3 garages for a university with just the standard type wabocrete joint, no steel rails, and after about 10 years of use they were not leaking and in generally good condition except for some nicks in the top of the multicell gland, but because it was multicell it did not leak. One of the 3 was not multicell, just a V shape, and that had no damage, and no leakage, so that seemed the best, but would not be acceptable in many garages because wheelchair wheels can get caught in it and spill the occupant over. But perhaps the roof level of parking was not used in the winter ...I do not know...the seal condition seems to good to be true, so that is why I wonder if it is used in winter. I should drop around these garages this winter and see if the roof level is full with cars. On the other hand I have seen many joints of that type leak, even in floors not subject to ploughs.

 

[bridgebuster]

In Connecticut, the DOT would sometimes weld narrow plates along armored joints to raise the blade and prevent the seal from being ripped out. Installing armored joints for a 1" opening isn't worth it, in my opinion.

 

[ajk1]

Does anyone have a section thru a bridge expansion joint, so I can see what it looks like?
Also, what is the minimum concrete slab thickness that would be required to install a bridge expansion joint?
Also, what is the approximate cost range that they fall into?
What is their intended service life?