Mechanical Properties and Carbon Sequestration Performance of Cemented Paste Backfill Under Periodic Cyclic Carbonation Curing

To investigate the influence of periodic cyclic carbonation (PCC) curing on the mechanical properties, carbon sequestration rates, and microstructure of cemented paste backfill (CPB), this paper prepared CPB specimens of different cement/fly ash (CF ratios) and treated them by periodic cyclic carbonation curing. Afterwards, uniaxial compression strength (UCS), digital image correlation (DIC), and thermogravimetric (TG) analysis were conducted on them. Through the above tests, the following conclusions were obtained: (1) After the first PCC curing, the strength of CPB specimens decreased, with the Group M5 experiencing a 26.71% reduction. Following continued standard curing, the strength of Group M5 increased by 13.79%. After the second carbonation curing, the strength of Group M5 decreased by 24.43%. (2) The carbon sequestration rates of CPB specimens increased with the number of cyclic curing cycles but decreased with higher fly ash content. After the first PCC curing, the carbon sequestration rate of Group M5 was 7.201%, while that of Group M4 decreased by 0.53%. After the second PCC curing, the carbon sequestration rate of Group M5 rose to 7.470%, whereas that of Group M4 decreased by 0.51%. (3) Scanning electron microscopy (SEM) revealed that C-S-H gel formed in the PCC curing scheme after standard curing, while CaCO 3 formed after carbonation curing. The porosity of Group M5 was 8.402% after the first PCC curing cycle and decreased to 7.574% after the second PCC curing cycle, indicating optimized pore structure.