No, I haven't mixed that particular mixture of materials for making a cement, but I've most certainly mixed my share over the years of various types of cement, for all sorts of reasons. It doesn't actually matter what the cement is, it still doesn't mean that it will be indistinguishable from a natural rock. It may have rock like properties, but that's about it. They use calcined gypsum to strengthen adobe, sometimes. I'm very aware of its properties. However, it is not limestone nor Aswan granite (in this case). You can't even reproduce the sedimentary features present in the natural rock. You most certainly can't reproduce the crystal growth and any structures present within igneous rocks. I've had friends try and pull that trick on me, as well as pulling that trick on others myself. It's never worked.
What you have done is interesting, but you are yet to be convincing so far as it being the method used to build the pyramids. I will say though, it would be interesting to obtain enough material to have a go at building one of the pyramids. I'd be in it if someone had a go at doing it:):)