Hollow Core Slabs for Lubrication Garage Floor

[ajk1]

Has anyone used hollow core slabs with cast-in-place topping for a lubrication garage suspended floor with basement below? This would be the type of garage with several bays where you drive in for oil change etc., and then drive out.

The topping would be about 4" thick.

How would the floor be made so that the corrosive water with deicing chemicals tracked in during winter, did not leak thru the floor and cause corrosion of the bottom steel in the precast?

How was the topping treated above the longitudinal joints in between precast hollow core units?

Did you put a waterproofing membrane on the floor as per CSA Standard S413 "Parking Structures"?

I have been asked to review such a design.

 

[KootK]

You helped me through a precast hollowcore parkade ramp a while back. In the end, the precasters themselves didn't recommend it without a membrane and a topping above it. As such, I'd be concerned.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[ajk1]

ok, thanks. That is exactly what I told the engineer who asked me to review it.

 

[JAE]

I would do what KootK suggests. Use a 2" thick min. structural topping and then cover with a waterproof membrane system - then cover that with protection boards or something similar. Then a "pavement" slab - perhaps 4 to 5 inches thick with control joints as necessary.

The challenge even with that is to get any water to drain properly as the HC will have some camber and any water penetrating the drive surface slab will tend to slope downhill towards the ends of the planks. You can specify a variation of structural topping thickness to direct any of that water to drains placed in strategic locations. (Carlisle has some systems - CCW 500 - see here: Link)

Alternatively you can top the HC with a structural concrete topping and then use a traffic bearing waterproof system on top - the advantage to that is it is easily repaired if the membrane gets worn (which it will) - the disadvantage is that the membrane will get worn. (See Neogard, BASF, or other similar products)

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[msquared48]

I think that you may still have s lot of CIP as some PS planks have as minimum casting length. I have done a couple of these myself, too.

Concrete Tech in Tacoma, WA, has a minimum length of around 14 feet.

However, Central Premix in Kent, WA, (now defunct), had no minimum on the length.

So, it depends how they are reinforced and made.

Mike McCann, PE, SE (WA)

 

[ajk1]

To msquared48:

In the case that I am reviewing, span is 30 feet and hollow core is 12" thick.

For the couple that you did, did you:

a) use a traffic bearing waterproofing membrane?
b) tool joints into the cast-in-place topping to correspond with longitudinal joints between adjacent hollow core slabs, and fill the tooled joints with sealant?
c) go back a few years later to see how it is performing? Any leakage below?
d) Does Tacoma WA get a lot of snow and use deicing chemicals on the roads in the winter?

To JAE:

You would have a total concrete thickness of 12" precast (to span 30 feet) + 2" c.i.p topping + 4" to 5" pavement slab = 18" to 19" total. Have you done any detailed cost comparison of that to a cast-in-place reinforced concrete system with traffic bearing traffic topping waterproofing membrane system? I realize it saves forming costs, but makes all else more difficult.

I wonder if these structures are ever done as galvanized steel beams with galvanized checkered plate floor? Seems to me that is what I saw when I last had my oil changed, but did not take a close look.

 

[msquared48]

Can't be much help with a or b. Sorry. The ones we did were CIP due to the span length limitation. Not enough PC plank to make it pay.

Rarely do I get an opportunity to see anything built from what I have designed. I have gone back in prior years to take pictures of past projects though for marketing, but not the lube projects.

Tacoma does get some snow, but nowhere li8ke the Midwest or Northeast. Some deicing is used, mostly applied before the snow hits.

Mike McCann, PE, SE (WA)

 

[ajk1]

OK, that is interesting information. Much appreciated.

 

[JAE]

Just did a roof over a service garage that had parking on top. We used the Carlisle system due to also wanting to have insulation between the structure and parking deck.

The costs are probably a bit smaller with the traffic bearing system but that system requires a bit more maintenance over time so when you look at life cycle costs they may be similar.
With traffic bearing systems, whenever you get repeated wheels turning in the same location the membrane wears off. It is nice that you can see the wear and respond to it.

The downside of the membrane system under the parking deck slab is that if there's a leak showing up below, you really have no idea where the leak actually is located in the membrane above due to sideways water migration in the system.




Check out Eng-Tips Forum's Policies here:
faq731-376

 

[ajk1]

To JAE - yes agree completely with what you say. Not sure what the Carlisle system is. Is it a polyurethane waterproofing membrane? Was the roof that you just did cast-in-place or precast? If it was precast was it double tees, or hollowcore?

 

[JAE]

Roof was precast double tees with a structural topping.

Carlisle CCW system: Carlisle CCW-500

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[ajk1]

ok, yes I have done precast double tee garages with cast-in-place topping, quite common. But I have not put a hot-applied membrane on top, although would be good added protection since the joints in the precast system end up leaking. I have done lots of hot applied membranes, and cold applied, but on cast-in-place structures. But hollowcore slabs are a different thing than the double tees, and even more difficult to make the longitudinal joints between units watertight. It was hollowcore that was used on Algol mall, that was constantly leaking and eventually a part collapse, killing 2 people. I think it is a mistake to do a lube bay garage as hollow core.

 

[JAE]

But hollowcore slabs are a different thing than the double tees, and even more difficult to make the longitudinal joints between units watertight.

Well, without a structural topping and a waterproof membrane I'm not sure I'd even consider the HC system water tight anyway.

The system I linked to, or many other similar systems, should be used with DT's or Hollow core if you want a waterproof system.



Check out Eng-Tips Forum's Policies here:
faq731-376

 

[jike]

The membrane needs to be tied into floor drains to drain any excess liquid that gets below the topping.

 

[allgoodnamestaken]

Every time I read about using precast components with corrosive environments and depending entirely on membranes I am reminded of the Elliot Lake/Algo Centre Mall disaster. That particular case was largely an issue due to the owners and engineers involved passing the buck and not doing maintenance/inspection as required, but it does highlight potential issues with relying on membranes and inspections in known corrosive environments. May be completely useless to you, but I think it's an interesting event.


Wikipedia

https://en.wikipedia.org/wiki/Algo_Centre_Mall

Official inquiry report available here

http://www.attorneygeneral.jus.gov.on.ca/inquiries/elliotlake/report/index.html

edit: I see this has been mentioned a few posts up by ajk1. I'm still going to leave it here.

 

[JAE]

Any system, steel, cast concrete, precast, etc. which is exposed to water/salts and not maintained by its owner can collapse.
That mall collapse wasn't a verdict on precast, only lack of proper maintenance.



Check out Eng-Tips Forum's Policies here:
faq731-376

 

[ajk1]

To jike - yes you make a very good point. Thanks for the reminder.

To allgoodnamestaken : There was never any waterproofing waterproofing membrane on the Algo Mall, so I am puzzled about your reference to the Algo Mall depending on a waterproofing membrane. Please refer to CSA Standard S413 "Parking Structures" for what is required for proper parking garage design for durability. Waterproofing membranes have proven their value in millions of square metres of parking garages in Canada. Of course they need to be maintained.

To JAE: The Algo Mall collapse was due to many factors. Many of the factors could be grouped under the rubric of "lack of proper maintenance". But if the garage is designed so that it leaks from day one, then the owner was never provided with a garage that could be maintained in accordance with any reasonable maintenance program. I would say that it was (mainly?) a matter of lack of proper design (i.e. a failure to provide the owner with a garage that did not leak and could be maintained).

Certainly it is a challenge to render the joints in precast construction watertight, so from that point of view I prefer a cast-in-place garage, and that has informed my thinking in the several million square feet of parking garages that I have designed in Canada in the last 30 years.

 

[JAE]

Certainly it is a challenge to render the joints in precast construction watertight, so from that point of view I prefer a cast-in-place garage

If you put a cast topping on the precast there is essentially no difference between cast and precast in terms of water tightness. Concrete is nothing but a hard sponge in reality. To ensure water-tightness some system beyond the concrete itself is needed, whether precast or cast-in-place.

But if the garage is designed so that it leaks from day one...

Yes - a bad idea.

There are millions of square feet of precast garages built that have done quite well over the years when maintained properly.

Check out Eng-Tips Forum's Policies here:
faq731-376

 

[allgoodnamestaken]

@ajk1 - not correct, there was indeed a waterproofing system at the Algo Centre. Certainly the lack of maintenance had lots to do with it, but you as the designer have zero control over future maintenance.

http://www.attorneygeneral.jus.gov.on.ca/inquiries/elliotlake/report/Vol1_E/ELI_Vol1_Ch04_E.pdf

Page 93 starts on the waterproofing system. There were lots of problems with it, but it did exist.

 

[ajk1]

To allgoodnamestaken:

Your post said "Every time I read about using precast components with corrosive environments and depending entirely on membranes I am reminded of the Elliot Lake/Algo Centre Mall disaster". I bolded your use of the word "membrane".

According to the report that you attached (and thanks for that) as well as my other information that I know about it, there was very clearly and unequivocally no waterproofing membrane on the general floor area of the Algo Mall.

The joints were treated with sealant (caulking) and all the remainder of the the area was treated with a sealer (not a membrane). This was known as the Peterson system. This is not a waterproofing membrane as defined in CSA S413, or as any disinterested engineer experienced with parking structure design would understand it.

The following pages after page 93 are also interesting reading, especially where it says the caulked joints system was not intended for precast slabs, but only for double tees. That sounds very similar to the point that I made in my earlier posts in this string.

I don't want to get into an endless back-and-forth time consuming debate on this, so if you still disagree with me, that is fine and I respect you for your views. I am the first to admit I am not always right, and we can just agree to disagree. Thanks for your comments. Much appreciated.