Since Elsevier is hiding the meat in that journal article, I can only go off what I read, but it looks identically flawed.

• Compressive strength of normal concrete: 25-50MPa

• Compressive strength of their slag concrete with 2h CO2 added: 12MPa

• Compressive strength of their slag concrete with 24h CO2 added: 24.3MPa

My takeaway:

Using slag instead of cement = good idea.

Using slag OR cement plus CO2 = bad idea.