Paving on Foamular Styrofoam Insulation 1

[smp123069]

We have a situation where we need to fill a void on top of a garage slab that has already been poured with a ligth weight material that has sufficient strength to act as a road base. It has been suggested that we use a styrofoam product like Foamular from Owens Corning. We plan on providing a drainage board on top of the structural slab, 2-16" of the foamular board, 4" VDOT 21A open graded aggregate, 5" base asphalt and 2" of surfact asphalt. Does anyone have any experience with paving on such a system? It appears from the literature on the product that it should have sufficient strength (up to 100psi). My only concern is that the aggregate may damage the styrofoam boards to a point where they are no longer able to function as intended and deliver the compressive strength that we need. It has been suggested that we provide a filter fabric on top of the styrofoam board layer to reduce the damage done when the aggregate layer is distributed over the foamular product.

 

[LCruiser]

Sheesh. How about a picture? A void on top of a garage slab?

 

[smp123069]

I'm sorry if I wasn't clear with my post. Maybe, "void" wasn't a good way to describe the situation. The original pavement section was intended to be this (from the bottom up).
top of garage deck slab
waterproofing drainage board
4-18" VDOT 21A well graded aggregate
5" base asphalt
2" of surface asphalt on top

The issue is that the structural engineer didn't realize that there was going to be such a deep layer of the aggregate and we are now having structural issues in that we are over the design load of the garage slab.

We would like to substitute 2-16" of geofoam of some sort to bring the grade up so that we only need to apply 4" of the aggregate to pave on. I don't have any experience with this type of application so I was throwing the topic out there to see if anyone has had experience with this type of application. I am wondering if there are any design issues that I should be concerned with. Also, is 4" of the aggregate stone sufficient?

 

[eric1037]

Have you considered an expanded shale aggregate such as Solite or Haydite in place of the styrofoam? Maybe even a flowable, lightweight fill would work.

Also, making your asphalt section thinner by using a geogrid reinforcement in the aggregate would lighten things up significantly. I find it difficult to believe that you would need that thick of an asphalt section if you are putting it on gravel with concrete under it.

 

[smp123069]

Thanks for the reply Eric. Yes we have looked at using LWA such as Norlite or Stalite. They are approximately 60 lb/ft3 and are still do heavy for our section. The foam boards are only about 2 lb/fts and provide compressive strengths up towards 100 psi.

We don't want to modify the 7" of asphalt since this has been specified by the jurisdiction and would require an admistrative change that could take some time and may not be approved. We don't have the time to go through this process. We do have approval from the County to provide the 7" of asphalt on top of a subbase with a CBR of 30 or higher. We feel that we would be meeting this requirement if we provide the 4" of aggregate on top of the geofoam. My biggest concern is whether or not the 4" of aggegate is of sufficient depth to protect the geofoam. Also I understand the the aggregate will depress and puncture the geofoam when the aggregate layer is compacted. We intend on providing a filter fabric on top of the geofoam to help reduce the amount of damage to the geofoam from the compaction of the aggregate.

 

[jheidt2543]

Just a few things to consider:

I have used the Formular as a "filler" under cast-in-place concrete a few times with no problems, as you mentioned, there is plenty of compressive strength. I've never seen it used under asphalt, but it is possible.

In your case, I would be concerned with two things:

1. The aggregate punching the styrofoam, as you have already mentioned. The problem is the point loading of the aggregate pieces and I'm not sure if a geotextile would provide enough protection. The size of the stone fill could be a factor. I think you could easily try this out in a small experiment, say one 4x8 sheet, with a 2x12 around the edges to confine the stone, then cover with the stone and run a compactor over it, then check for damage.

2. The heat generated by the hot asphalt may also damage the board. Here, the product data should have what the melting point is and the minimum thickness of the aggregate could be selected to resolve the heat transfer problem.

Just adding my two cents!

 

[smp123069]

Jheidt2543, Thanks for your input. I have spoken with a paving company and they don't anticipate any problems with that paving and the heat transfer through the 4" of aggregate.
SMP

 

[civilperson]

You do not need the aggregate, the CBR of the foam is sufficient if a fabric is used to cross the joints.