You could try it. I don't believe that anyone has before. However concrete tends to leech for years in the natural environment. What we are doing with DIY Rock is an unnatural thing for concrete and already rushing the process. It will be fine and then sometime down the road it can jack up the alkalinity seemingly out of nowhere. The reason that this would happen is because it wasn't fully leached out during kuring.Sorry, i should have been more specific. I did NOT mean to mix the superbuffer powder into the dry mix of portland etc....
What i ment was, in the Kuring tank, i could dissolve superbuffer into the RO/DI water.
Simple principle of diffusion: the larger the gradient, the greater the diffusion rate. This is also likely why agitation of the water (using a circulation pump in the container) during Kuring is found to be "preferred". The buffer will serve to maintain the liquid's pH to the ideal 8, and the higher pH cement will leech faster because the water isn't being allowed to increase pH (by virtue of the buffer) as leeching occurs, thus maintaining the gradient.