I've read all the other comments on your post, as well as your post. My question to you was why is the water use at the point of mixing a problem in this scenario?
Every 100-pound bag of conventional cement requires 5.2-gallons of water to mix. The annual water amount needed to create concrete is equivalent to the consumption of water by 145-million people.
However, upon doing some digging, I found that OPC requires water as part of the chemical reaction that makes concrete...concrete...
Tricalcium silicate + Water--->Calcium silicate hydrate+Calcium hydroxide + heat
Chemically:
2 Ca3SiO5 + 7 H2O ---> 3 CaO.2SiO2.4H2O + 3 Ca(OH)2 + 173.6kJ**
If this is the case, water is required to cause a chemical reaction binding the tricalcium silicate.
However, I'm glad you mentioned Solidia:
“Solidia Cement™ is a non-hydraulic cement composed primarily of low-lime-containing calcium silicate phases, such as wollastonite / pseudowollastonite (CaO•SiO2), and rankinite (3CaO•2SiO2). This contrasts with the high-lime alite (3CaO•SiO2) and belite (2CaO•SiO2) phases that comprise OPC. The setting and hardening characteristics of Solidia Cement are derived from a reaction between CO2 and the calcium silicates. During the carbonation process, calcite (CaCO3) and silica (SiO2) form and are responsible for the strength development in concrete.”
https://assets.ctfassets.net/jv4d7wct8mc0/5DwEAeEYqsFAYA9UC53EF7/4f8b7566221a8d9cb38f970867003226/Solidia_Science_Backgrounder_11.21.19__5_.pdf
The pdf says there is a liquid solution that is used; however, based on the chemistry, no water is used in the chemical reactions; therefore, you can make concrete without water.
I like that you brought this to my attention. It made me go down a rabbit hole. My impression had always been that the water used in making concrete simply evaporated, therefore the use of water was not an issue. I don't have a problem with heat sources creating CO2. I know that in some cases, the product used to create the CO2 in the first place could have been pulled from the air, like renewable natural gas. When natural gas burns, you get water vapor and CO2. The world recycles itself :)