Mortar or Concrete bed? For sloped shower pan.

Hi All,

Just finishing my wet room. I have a linear drain in the end embedded and secured levelled into the concrete floor. I am now ready to do the wet room slope pan. I have placed two pieces of strip wood on each side and raised them accordingly to my slope measurements. I will use these strip woods to screed level the slope.

Because the floor is a concrete base. Should I pour a ready mixed concrete bag instead of making a mixed mortar of only sharp sand & cement.

I feel concrete has higher strength than a mixed mortar. Especially with concretes addition of other additives. As long as I mix it to a consistency that holds but is not runny.

if not, then what would you do?

Your thoughts on this. Photos below. Thank you in advance to all.