Study on activation and performance of recycled hardened concrete powder based on microbial accelerated carbonization

Recycled hardened concrete powder (RHCP) was used as a raw material, and microorganisms were introduced to accelerate carbonization to enhance its activity. The carbonation ability of RHCP was investigated by altering the solid-liquid ratio during carbonation. The results indicated that the carbon sequestration amount of RHCP after 7 days of carbonation at room temperature and pressure initially increased and then decreased with the rise of the solid-liquid ratio. When the solid-liquid ratio was 1:0.8, the carbon sequestration amount of RHCP was the highest, reaching 208.65 g/kg. The carbonized RHCP (C-RHCP) and RHCP were then used to partially replace cement to investigate their effects on the workability, mechanical, and durability properties of the mixtures. The results showed that when the replacement amount of C-RHCP was 30 %, all the properties were relatively good. The water demand and setting time were not significantly different. After 28 days of curing, the compressive strength of the 30 % C-RHCP specimen reached over 70 % of that of the pure cement group. However, its carbonation resistance was significantly lower than that of pure cement, while its resistance to chloride ion penetration and drying shrinkage was similar.