Preparation method of negative carbon cemented filling material

The invention discloses a preparation method of a negative carbon cemented filling material, which specifically comprises the following steps: firstly, mixing and stirring fly ash and water to prepare fly ash slurry; conveying the fly ash slurry into a high-pressure reaction kettle, introducing CO2, and continuously stirring the slurry until the pH change amplitude of the slurry is less than 0.02/min; carrying out pH detection on the fully reacted fly ash slurry, if the pH is less than or equal to 9, directly entering the next step, and if the pH is greater than 9, adding an additive into the fly ash slurry until the pH is less than or equal to 9; and conveying the fly ash slurry with the pH value reaching the standard to a secondary stirring system, adding aggregate and cement, and stirring to prepare the negative carbon cemented filling material. According to the preparation method of the negative carbon cemented filling material, a CO2 mineralization technology and a fly ash modification technology are fus