Due to the chemistry, lime (like crushed limestone) is basically calcium that hasn't been dehydrated to make cement. Borax has a lot of boron in it, and that is what makes it toxic to insects. So the answer is no, they are not interchangeable even for the insect properties. Borax seems to take less of it to make wood (paper?) fire resistant.
I have seen on some log home forums where folks will spray or dip logs in a borax and boric acid solution (like 1C Borax, 1/2 C Boric acid, to 1 gal of water solution) to soak the logs. Also doing a similar thing using 'water glass' (sodium silicate) does even more to make it fire resistant (I understand insects don't like it either). Termites don't like it because it basically adds silica (think fine sand or ground glass) to the surface of wood). A friend that sells chemicals to the concrete industry told me they add sodium silicate to cement when making concrete blocks. This is what allows the basically porous concrete block to become 'water resistant' over time if the blocks are rained on occasionally. (sorry, I seem to be a factoid monster recently).
If you know someone at a concrete block plant, you might be able to get the end of a container cheap/free. I got some of the cube type 400 gal totes that were used for the concrete additive, and they had a couple of gallons of chemical left in the bottom of the totes. We just poured it out on the ground (considered non-toxic by the EPA. Still don't go drink the stuff, but diluted it won't kill you, according to the MSA). ... we got the tote to haul water for horses after we washed the tote out pretty well. Also have used it to haul water to put into concrete mix setting some new fence posts, especially since it fits nicely on fork lift tines we put on the a tractor. Just handy to have around.
><> ... Jack
Whatever you do, work at it with all your heart... Colossians 3:23
Borax is expensive. Lime is cheap. Don't you think lime would do the same, fire and insect proof?Joy
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