Fake rock structures

[jackdogga]

Hi, i want to do some making in the holidays like caves, hides and other stuff for my frogs. I saw a video on you tube where the guy makes hides out of grout, grout sealent and expanding foam. I was wondering what the best grout and grout sealnts are and where i might get them. If anyone makes things differently please tell me your way. Thanks ps. im in australia