Hi @aaron.vaden-youmans - my understanding is if anything the opposite is true: mixes with cement replacement tend to have a higher long-term strength. The issue is more with early strength, which can be an issue for elements like PT slabs where you need to strip forms fast to keep schedule.
Couldn’t find any research on-hand to back this assertion up, but maybe some people smarter than me can share their thoughts and data! @aguzzetta @nicholas.miley @megan.stringer @dkestner @ddavies
If long-term durability is a driving factor, you may also want to consider concrete cover on the rebar depending on exposure and environmental factors. I’m not familiar with rail projects, but maybe others have more to contribute on this topic as well.