Is sand mix concrete appropriate for a shower floor?
in a normal curbless install you want a 100% sealed system. it sounds like this over a concrete substrate, so once the drain is  installed and secured, use a mud bed mix thats been fortified or add a latex into it, this will help with strength as the pitch gets shallow. in addition to latex in the mud bed, trowel mortar to the cement before the mud to help it bond to the cement.be sure to dampin the cement before combing mortar on it, so it doesnt suck the moisture out of it to fast and weakin its strength. after that its all about the water proofing, several options there from roll on to fabic membrains. choose the one you feel u can manage the best. showers are all about being water proof, if u cant take a shower before the tiles up without it leaking, then its not ready for tile.