it's perfect.
cement is a powder made from limestone, it's one item.
mortar is cement and some sand. It's two things together.
concrete is cement, sand and stones. It's three things together.
The kind of sand you use in this situation will not have any great difference on the outcome. If you wash the sand a bit, by putting it in water and spraying the end of the hose into the water to stir it up you'll see if it is dirty sand by the water getting cloudy. If the water is clear or becomes clear with the swirling, then the sand is just fine. Small amounts of dirt don't matter.
What DOES matter a million times more is reinforcement for the concrete floor. If you don't put any mesh into it, it will crack and the cracks open up over time.
You can get reinforcement bar called 'rebar', about as thick as a pencil and holes about the length of a pencil on each side which you put into the concrete and never have to worry about cracking ever. You put a few barrow loads or a dozen shovels full of wet concrete on the floor and when you're about half the thickness you want, you place the mesh onto it. The idea is that it will be in the middle of the concrete by the time it's all done. Cut whatever mesh you use so that it doesn't reach all the way to the edges of the concrete. You want at least an inch or better two inches of concrete all around the edges of the mesh so that scratching the concrete can't expose the mesh.
You can use a few layers of chickenwire as your mesh if you have nothing else. Fencing wire is good too. avoid heavily rusted wire or iron or steel, but a tiny bit is ok, like a new piece left out in the rain has a 'little bit' of rust after a week, not a corner is rusted away 'little bit'.