In making up cement-based mixtures, I always start with a water:cement ratio of 0.42:1, which is the optimal ratio. But whenever I make a mix that has a substantial quantity of sand in it (e.g. for mortar, or a self-consolidating pourable thing) the sand seems to gobble up all the water and turn the mixture into a gritty, unworkable paste. I always need to add a substantial amount more water to make it workable, which I know weakens the mix.
I've tried commercially-packaged masonry sand, sieved sand from my backyard, and the texturing sand I had in an old package of paint texture. Same diff, though it was worst with the paint texture stuff, which was very fine and dry.
I tried adding a commercial PCE superplasticizer (0.5% by weight) but it didn't seem to make any difference at all.
I don't have an electric mixer, so I have to do the mixing by hand. Could my technique be the problem?
Also I live in the desert so everything here is just naturally dry all the time; could it be that most people's sand has more moisture in it?