RHO & The Perfect Aggregate?

Hmm, this kind of makes me wonder what the RHO for portland cement is, since it is the only component in concrete that has continuity.

True-but regrettably we must also adhere to another spec that calls for no less than 4000 psi break strengths @ 28 days and be ASR non-reactive!

Hmm, these don't really seem directly relevent to the question. Consider a bunch of non-conductive plastic spheres placed in salt water. Is the RHO of the sphere going to have much effect on the overall RHO of the system? At some point small changes in the RHO of the aggregate will have no apparent effect if the concrete is substantially greater. In this case, what may have a effect could be the ratio of aggregate to cementitious materials though, by increasing the maximum size of aggregate and gradation in the mix. Something to consider. You can achieve 4000 PSI mixes and ASR non-reactive with a variety of different mixes comprised of different aggregate sizes and gradatations