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Carbonation curing can store CO₂ in cementitious materials, but its net benefit depends on emissions from CO₂ supply and curing. A curated set of 461 literature uptake records, harmonised to an original-material mass basis including aggregates, is paired with eight material and curing descriptors and eight compared regressors, then coupled to supply, transport and curing emissions. At an illustrative predicted uptake of 0.231 kg CO₂/kg original material and an assumed 2400 kg/m³ material mass, all five supply scenarios give net benefits of 0.189–0.219 kg CO₂/kg original material at 0.05 kg CO₂/kWh, two turn net emitters at 0.40 kg CO₂/kWh, and break-even electricity intensities range from 0.314 to 2.047 kg CO₂/kWh.
The net carbon benefit of carbonation curing is no longer read off the CO₂ taken up, but from that uptake minus emissions from CO₂ supply, transport and curing electricity in one balance. Earlier assessment treated uptake largely as the benefit itself, while supply-chain emissions and curing energy can change the comparison with conventional production. At an illustrative predicted uptake of 0.231 kg CO₂/kg original material and an assumed 2400 kg/m³ material mass, five supply scenarios give 0.189–0.219 kg CO₂/kg original material at 0.05 kg CO₂/kWh, and two become net emitters at 0.40 kg CO₂/kWh.
Uptake prediction rests on experimental records pooled across studies, each converted to an original-material mass basis that includes sand and aggregates. Reported uptake came on differing material and measurement bases, so direct pooling would mix composition and procedural differences. The working dataset holds 461 observations across 33 source identifiers, with uptake from 0.01% to 51.11%, a mean of 13.68% and a standard deviation of 8.03 percentage points.
The model behind the response surfaces has imposed response directions, so its uptake changes with water-to-cement ratio, pressure and exposure time are conditional scenarios rather than experimental optima. Under random five-fold validation the ensemble reaches R² = 0.737 and the constrained model R² = 0.632, but keeping source studies intact drops these to −0.086 and −1.540. On the grid at exposure times of 2, 24 and 48 h the constrained model gives fitted uptake of 9.55–23.13%, 18.68–30.72% and 22.66–35.25%, reported as conditional predictions.
The accounting boundary covers CO₂ supply and selected curing operations; it excludes binder production, infrastructure, service life and end-of-life behaviour, and includes neither a strength-equivalent comparator nor an assessment of leakage and long-term storage permanence, so a positive process balance does not establish a carbon-negative product. It is aimed at researchers and engineers assessing process emissions of carbonation curing, and the 2400 kg/m³ material mass is a scenario assumption rather than a measured density.
When source studies are kept intact, R² falls to −0.086 for the ensemble and −1.540 for the constrained model, which the authors read as no validation for prediction in a new study. The constraints fix response directions but cannot compensate for omitted composition variables, measurement differences or gaps in joint coverage, and vacuum demand below 1 bar is omitted, leaving that part an incomplete-energy scenario.
