Frost Protection for Truck Loading Slab

[Canucks1010]

Hello.

I have a truck loading slab that is susceptible to frost heave (3'-6" frost depth). One engineer is recommending the following to mitigate potential frost heave, but I have my reservations:

1. Place 2 ft of CLSM (flowable concrete fill) below the slab. The intent is this fill acts as a "non-frost susceptible fill" material.
2. Place Ethafoam insulation underneath the CLSM to insulate for frost heave. The insulation extends beyond the slab. The thickness and extend of insulation is optimized considering the CLSM provided some insulating cover.

My reservations are:

1. CLSM cannot be considered a substitute for soil insulating properties. The R-value of CLSM can be as low as 0.1/inch, compared with 0.25/inch for soils. This increase in thermal conductivity should be considered, no? It can extend the assumed frost depth.

2. Ethafoam was selected due to potential for hydrocarbon spills. However, I don't believe Ethafoam is rigid, rather is compressible - therefore, it should not be used for truck loading. A rigid product like Styrofoam HiLoad 60 would be much better - but it is susceptible to degradation due to possible hydrocarbon attack. Any comment?

Perhaps using a concrete insulating material like Cematrix would be more appropriate?


Thank you for the input!

 

[JAE]

We have used flowable fill under exterior door stoops for frost mitigation.

Another thing you might consider is Expanded Polystyrene. You can get custom fit-to-space blocks that are traffic bearing.
They are also susceptible to petroleum degradation so we've typically covered them with a competent vapor barrier-like membrane
and sloped the top to drain off any spills away from the foam blocks. The flowable fill goes on top, then perhaps a granular layer and the pavement.

 

[dik]

Can you use a high load polystyrene insulation to trap the geothermal heat? DOW has some excellent literature on this.

 

[Canucks1010]

We have used flowable fill under exterior door stoops for frost mitigation.

Another thing you might consider is Expanded Polystyrene. You can get custom fit-to-space blocks that are traffic bearing.
They are also susceptible to petroleum degradation so we've typically covered them with a competent vapor barrier-like membrane
and sloped the top to drain off any spills away from the foam blocks. The flowable fill goes on top, then perhaps a granular layer and the pavement.

Thank you for your input! I will suggest the use of a vapor barrier for protection as you proposed.

 

[Canucks1010]

Can you use a high load polystyrene insulation to trap the geothermal heat? DOW has some excellent literature on this.

Agreed with the use of high load polystyrene. As JAE suggested, due to petrochemical exposure, I can propose the use of a vapour barrier to protect.

 

[JAE]

I'd suggest a very thick VB and/or use a protection board over it to avoid damage from any granular material you might use on top.