Enhancement of pozzolanic reactivity of waste autoclaved aerated concrete via CO2 aqueous carbonation: technical and environmental benefits.

Carbonated waste autoclaved aerated concrete (WAC) presents significant potential as a supplementary cementitious material for developing low-carbon cement. This work examined carbonation behavior of WAC subjected to aqueous carbonation under ambient conditions, analyzed the pozzolanic reactivity of carbonated products, and evaluated consequent economic and environmental implications in cement applications. Experimental results indicated that WAC exhibited remarkable carbonation reactivity under aqueous conditions, achieving 75 % carbonation degree with CO2 uptake of 14.65 g/100g WAC within 40 min. The carbonation products of WAC mainly consist of calcite and highly polymerized silica gel, which dramatically promoted the hydration process of cement. When utilized as supplementary cementitious material at 15 % replacement ratio, the 28 d compressive strength of carbonated WAC cement increased by 33.6 % compared to obtained WAC while its performance is comparable to that of OPC, simultaneously reducing production costs by 14.3 % and CO2 emissions by 16.8 %, demonstrating its dual economic and environmental advantages for sustainable cement production.