Key points are not available for this paper at this time.
This study explores the production of lightweight carbonated geopolymer aggregates from class F fly ash (FA) and calcium carbide sludge (CCS) via carbonation. The carbonation processes, conducted under 99% CO2 concentration and 65–70% relative humidity at 4 bar , resulted in complete carbonation within 12 h, with CO2 uptake of 13.3%. The conversion of Calcium-Aluminum-Silicate-Hydrate (C-A-S-H) gel formed in non-carbonated aggregates into the Sodium-Aluminum-Silicate-Hydrate (N-A-S-H) gel in carbonated aggregates enhanced single aggregate strength by 78.6% . FT-IR results revealed the formation of C-A-S-H gel in non-carbonated aggregates, while after carbonation a shift in the Si–O–T (T = Al or Si) vibration band towards higher wavelengths due to the formation of N-A-S-H gel. 29Si NMR further confirmed that after carbonation Q2(1Al) peak in non-carbonated aggregates was diminished and an intense Q4(3Al) and Q4(1Al) peak were observed in carbonated aggregates. This conversion inhibited the leaching of sodium ions which completely resists the efflorescence problem related with the geopolymer aggregates.
Hanifa et al. (Wed,) studied this question.