yes most of "cement"first sets due to hydration ,ie roast it ,water gone ,water back,it sets
the bit that releases co2 (ie the ca co3 to ca o )will react with environmental co2(ie same amount as roasted out )
unless im very wrong the long term co2 footprint of either lime or "cement"(there are lots of subcatagories) depends on the energy sources used to mine,transport and to roast the stuff.
cement chemistry is complex but the basics are if it gives off co2 from the minerals it will take them back
this is one reason "cement"continues to gain cohesion (if the dampness/access to environmental input is there)