CO2 carbonation process of cemented paste backfill material using polycarboxylate ether (PCE) and MgCl2

• CO 2 carbonation process on cemented paste backfill material reaction mechanism. • An analogical study with polycarboxylate ether and MgCl 2 . • This novel method shows significant results of CO 2 adsorption in backfill material. • Dosage of PEC and MgCl 2 increased the UCS by approximately 80%. • First time highlighted the classification of pore geometrical structures. The challenges of CO 2 sequestration are advancing rigorously in every field, yet the technical approaches are lagging behind the carbon emission rate. The carbon mineralization of cementitious materials is also considered a major contributor to carbon footprints due to the consumption of large quantities of Portland cement. Understanding these significant issues, we employed environmentally friendly materials and treatment methods, specifically PCE and MgCl 2 , to enhance CO 2 sequestration, improve workability, and increase durability in cemented paste backfill material (CPBFm) for underground mining. PCE (0.5–2.0%) and MgCl₂ (0.2–0.8%) improved cohesion strength of backfill material (BFMT). After CO2 carbonation process in BFMT samples, the dosages of PCE and MgCl 2 effectively controlled slurry rheology; increasing dosages reduced shear-thinning stress and prevented the excessive water demand, poor dispersion, and premature setting seen in untreated samples. We propose that PCE side-chains (COO⁻) interact with Mg²⁺ to reduce dispersion, decrease voids and large pore channels, and thus enhance mechanical interlocking. These treatment methods improved the unconfined compressive strength (UCS) by approximately 80% and enhanced CO 2 uptake efficiency, with carbonated samples averaging 7.89 mg-CO 2 /g compared to non-dosed samples, which averaged 4.60 mg-CO 2 /g. Visual SEM observations of micropore structures revealed that the dominant pores were cylindrical, wedge-shaped, and channel-like. Low-temperature N 2 adsorption capacity analysis indicated a higher surface area in PCE and MgCl 2 -based samples. This analytical approach to hazardous materials improves sustainable backfilling and carbonation processes in underground mining operations, with potential for industrial scaling.