Performance-Normalized Cradle-to-Gate Carbon Screening of Polymer-Modified Cementitious Repair Mortars Using Standardized Functional Units

Polymer-modified cementitious repair mortars improve adhesion and durability but usually increase cradle-to-gate (A1–A3) emissions. This study develops a performance-normalized embodied-carbon screening framework that compares repair materials on standardized functional units (1 m3, 1 kg dry mix, 1 m2 repair layer) and on declared repair functions. A database of 55 studies, 141 mixture records, and 243 endpoints was compiled, and 19 studies met predefined criteria for quantitative extraction. Two within-study case studies were analyzed, and emission factor and test-result uncertainties were propagated by Monte Carlo simulation. In epoxy-modified mortars (reconstructed inventory) exposed to sulfuric acid, modification reduced mass loss by 57.9–96.0% but increased emissions from 264 to 422–857 kg CO2e/m3; the 5% resin mixture had the lowest incremental carbon cost and the 20% mixture the lowest deterioration-rate-normalized GWP in >99% of simulations. In styrene–butadiene rubber mortars, the cationic latex reduced the chloride migration coefficient by 31.5% and, with a regional EPD, lowered the chloride-normalized GWP by 26%; this advantage is lost above a latex emission factor of 2.66 kg CO2e/kg. In a geopolymer benchmark, a declared desirability index ranked one of the same two mixtures first in all predefined scenarios. The framework supports screening rather than definitive ranking.