pH ‐resolved wet mineral carbonation of fly ash–carbide slag blends: CO ₂ uptake, carbonate

Abstract

Wet mineral carbonation can couple stable CO ₂ storage with valorization of fly ash (FA) and carbide slag (CS), but the influence of slurry composition on operational endpoint, carbonate distribution, and product performance remains uncertain. This study combined online pH monitoring, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, and early‐age strength testing to evaluate FA, CS, and FA–CS slurries. At FA:CS = 1:1, the time to pH 7.00 decreased from 790 to 650 s, a 17.72% reduction relative to CS alone. The blend showed a TGA‐derived apparent CO ₂ uptake of 25.76%, 14.54% above the corrected mass‐weighted expectation. Phase and microstructural observations indicated conversion of detectable portlandite and redistribution of carbonate deposits from CS‐rich aggregates toward FA surfaces, which may reduce product‐layer passivation. Moderate slurry carbonation also increased 3‐day compressive strength to 15.33 MPa at FA:CS = 6:4 after 50 min, whereas longer treatment reduced strength. The results define a composition‐dependent operating window for coordinating mineral carbon storage and early cementitious performance.