New slopes for suspended parking slab 1

[Robbiee]

Hi all,
We have an existing suspended two-way concrete parking deck slab that needs the surface slopes increase. The slab design loads are fixed and can't go over them. The design includes 4" of asphalt and max. 4" of gravel. However, to achieve the required slopes, we need up to 12" of gravel at some locations. The questions I have:
1- can we use an asphalt pavement that is placed directly on the membrane's protection board and at some point add rigid insulation to slope it up? or in other words, can be use a bonded system and unbonded system at the same deck?
2- If insulation can be used under the asphalt, how do we protect it from the heat of fresh asphalt?
3- Is there some type of lightweight granular, in stead of insulation, that can be used under the asphalt?
Thanks for all comments.

 

[dik]

Can the slab accommodate the added loading?

I don't know how to build up the additional slope; it appears to be quite a fill. The design of asphalt surfaces is a combination of all materials used in the construction. I don't know how foamed insulation will affect this. It is possible to get 'foamed' glass to use for loadbearing insulation. I don't know if it is possible to use a light aggregate and not affect the design. The change in elevation will have an impact on ramps, etc. that may be difficult to accommodate as well as any curbing at elevator and stair areas. Good luck... it'll be quite a challenge.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Robbiee]

Thanks dik
I was thinking of using the allowance for the 4" gravel for new light weight fill, insulation or lightweight granular.

 

[HTURKAK]

I would consider the use of foam concrete ( CIP) .. We have used this product more than 40 yrs ago for slope + insulation purpose on flat roof construction.

I do not know if available at your local market . But you may look for ( foam concrete , NEOPOR , Porenbeton). Light weight concrete can also be produced using light weight aggregate ( two of them ; expanded perlite aggregate , expanded clay ( keramsite ) aggregate )

The unit wt could be in the range of 400 to 600 kg/m3 .

The following doc. is attached for ONLY info.











I cannot give you the formula for success, but I can give you the formula for failure..It is: Try to please everybody.

 

[Robbiee]

Thanks HTURKAK.
Will check our market if something similar is available.

 

[dik]

The foam concrete as HTURKAK suggests with maybe a waterproof parking garage membrane directly over may be the lightest material.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Robbiee]

Thanks dik. I just emailed a supplier of foam concrete in my area and will see their input.

 

[Aesur]

Foam concrete is still quite heavy, maybe consider a lightweight concrete topping slab over Goefoam?

 

[BridgeSmith]

You'll need to look at what the thickness of concrete or gravel is required over the geofoam to distribute wheel loads. I think it's 12" for gravel; not sure what thickness of concrete is required.

Any possibility of raising the slab up on one end?

Have you considered using a structural concrete slab over, or adding a composite overlay?

 

[Robbiee]

Foam concrete weighing half of weight of gravel might work subject to the approval of civil and building science engineers.
Raising the slab on one end? Can't add enough concrete to achieve the slopes.
Adding composite topping is beyond the scope of this job.

 

[dik]

For the repair to work, it may be necessary to change the scope a tad...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Robbiee]

dik,
Agree, but adding loads means increasing punching shear and loads on columns and footings, which might not work. That is why we are trying to stick to a repair that is within the capacity of the structure.

 

[dik]

Yup... off the top, foamed concrete with a membrane is likey the best solution, weight permitting.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik