I've never actually measured the ingredients and compared them to the finished article (most of my stuff isn't solid), but I've read where you can measure all the dry ingredients when mixed together except the cement (because it fills the small voids & doesn't add volume), and that should give you an approximation of the volume after mixing.

Sue

That sounds workable. Concrete is easy, you get more or less the same finished product as the aggregate, the rest just fills in the gaps. Seems like I just have to decide which ingredients are the aggregate in 'tufa!