Floor mortar experiences dry shrinkage by temperature and humidity difference of internal matrix with material type. Also, since floor mortar is influenced by environmental conditions during placing and curing period, cracks are likely to be occurred. In this study, it was evaluated the hardening and dry shrinkage properties of non-sintered binder based floor mortar utilizing alpha-hemihydrate gypsum which has expansibility in order to prevent crack of the floor mortar. It was applied to the construction site, and examined the effects of external environmental conditions on shrinkage deformation and cracking. Different types of slag accelerated initial and final setting in comparison with cement mortar and its compressive strength was satisfied standard compressive strength for floor mortar. Also shrinkage deformation behavior after the initial expansion exhibited a similar tendency with the cement mortar. From the field application result, no crack was found from slag mortar, and it is determined that the slag mortar has better dimensional stability than cement mortar caused by external environment conditions.