###### Abstract  
In order to cope with climate change and achieve the goal of carbon neutrality, the use of carbonization technology to enhance the performance of cement-based materials and achieve the purpose of carbon sequestration has become a very promising research direction. This paper considers the use of CO2 NWB as mixing water for cement-based materials, aiming to improve the carbonization efficiency of materials to achieve the goal of carbon neutrality. This time, the effect of CO2 NWB on cementitious filling materials under different aggregate fractal dimensions was studied through uniaxial compression tests and acoustic emission technology. The effect of CO2 NWB on the mechanical properties and crack evolution of the material was discussed. The results showed that CO2 nanobubbles significantly improved the strength of cemented filling materials under different fractal dimensions, and the uniaxial compressive strength was most significantly improved by 23.04% when the fractal dimension was 2.7824. In addition, the characteristics of acoustic emission ring counts and energy parameters indicate that CO2 nanobubbles help improve the overall pore structure of the sample, affecting the macroscopic strength. However, the addition of CO2 nanobubbles reduces the limit energy storage ratio of elastic strain energy, which indicates that excessive CO2 concentration may affect the hydration reaction of the cementing material. c 2024 14 7792  
tailings, ordinary Portland cement and water. Their mechanical properties and durability depend largely on the material mix ratio and aggregate gradation [12; 13; 14]. Therefore, for this reason, many scholars have studied it from the aspects of cementing materials, aggregate gradation and admixtures. [PERSON] et al. [15] conducted a systematic study on tailings as alkali-activated materials. The results showed that tailings materials have effective cementing properties. In addition, they improved the mechanical properties of tailings cementing materials through different methods (admixtures, physical grinding and high-temperature curing). [PERSON] et al. [16] systematically evaluated the stability of cemented rockfill in filling mining strata through mechanical experiments and numerical simulations based on the optimization of aggregate grading. [PERSON] et al. [17] used aeolian sand-based material as the aggregate of the filling material and studied the transmission capacity and mechanical properties of the filling material by optimizing the ratio of the bonding material. [PERSON] et al. [18] developed a new type of cementitious material based on waste modified magnesium slag, fly ash and desulfurized gypsum. The research has been applied in field projects and meets safety requirements. The above research aims to reduce construction costs and reduce environmental pollution by selecting reasonable materials and ratios. However, CBM will inevitably produce CO\({}_{2}\) gas during the gelation process, which will have a significant impact on global warming [19; 20]. To better move toward a low-carbon society, the recycling of construction solid waste has become a hot research direction. Among them, the use of solid waste as an aggregate for cement-based materials has been studied by a large number of scholars [21; 22]. However, the bonding effect between recyclable aggregates and gel materials is significantly weaker than that between natural aggregates [23]. Therefore, relevant scholars have found that the early strength of recycled aggregates can be effectively improved by carbonization [24; 25]. In addition, the strength improvement of recycled aggregate cement-based materials through ordinary carbonization is limited, and the carbonization efficiency in this process is low. So, in order to reduce this impact, this paper introduces CO\({}_{2}\) nanobubble water (CO\({}_{2}\)NBW) as mixing water to provide an innovative solution for carbon sequestration. Nanobubbles are tiny bubbles with a diameter of less than 100 nanometers.