Ground Freezing - Insulation Of Concrete

[Ginger]

I am looking at brine freezing saturated ground in a ring around a tunnel in order to remove some damaged concrete rings. I intend to replace the damaged rings with an in-situ concrete ring. Can anyone advise me as to how I can insulate the wet concrete from the freezing effects of a ground at minus thirty degrees so that the concrete will cure and the heat of hydration does not begin to melt the ice wall?<br>
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Regards<br>
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Ginger