I've at the stage in a master bath remodel that I need to make a new shower pan. I plan on using a concrete base with tile, however is there anything "special" about the concrete mix I should know other than using sand?
Also is there any other way of sealing the concrete other than a liner that is available? I have seen a polymer sealant that is used to seal concrete floors from water but I am not sure it would be suitable.
Any help with the concrete mix and sealing would be much appreciated.
Thanks.

Take a look at this website: Shower Systems - Schluter-Systems (http://www.schluter.com/143.aspx)

Schluter detra, is a good shower sealer, that's what we use when the customers can afford it, its not cheap, they also make a drain for this system and it $100 easy,
I can't remember what the mat itself runs but you mortar this in and tile right after it, it comes with corner pieces where as the rubber membranes will bunge up in the corner making the tile angle out in the corners.

There is also a spray sealant it takes 3 coats to seal the shower, it go right over the durock backer board.
Other than those 2 methods is all we use. We don't use the rubber membrane anymore, but there's nother wrong with it, just be careful not to damage the membrane with droped tile or screws and nails on the bottoms of you shoes.

The special part is that we use mortar, not concrete. There is no aggregate in this cement. Consider this as an option if you have never done a pan from scratch. Swirl-Way: Alto 7514 Shower Base, Shower Bases (http://www.dougstubs.com/Bathroom/___Shower_Bases/Alto_7514_Shower_Base.aspx) If you really want to try mortar then read this. Building a shower pan with pre-sloped mortar bed, liner and curb. (http://www.ontariotile.com/preslope.html) I do mostly fiberglas and never have a problem.