Mortar?

[krnggangpe94]

Hi,
My dad has a bag of Versabond Mortar that he almost never uses. I want to build a styrofoam background for my leo and I know I need grout but can I use the mortar instead? Heres a link to the stuff he has: http://www.amazon.com/Versabond-Bonding-Mortar-MTSG50/dp/B000H5S8N4
Thanks!