Hello. I am heavily involved in the concrete lifting industry. We use polyurethane foam as was mentioned above.
Best thing to do is give me a call 403-461-2770 or send me an email
jon@ener-spray.ca with the details and we can chat about it.
I can give you some un biased answers and pricing.
Thanks
Jonathan
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No matter what the morrow brings, inventors keep inventing things.
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Jonathan
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www.cakerybakery.ca