The effect of carbonation pressure on microbial assisted steel slag-based carbon sequestration material

Abstract

This study investigates the factors influencing the application of microbial-induced carbonate deposition in the in-situ mineral carbonation process. Carbon-negative building materials are achieved by using steel slag powder as a carbon sequestering cementitious material and employing bacteria producing carbonic anhydrase to enhance the fixation rate of carbon dioxide (CO2). The primary focus is on understanding how different CO2 pressures affect the performance and carbon sequestration efficiency of this process. Our findings reveal that microbial-assisted steel slag exhibits promising potential as an effective carbon sequestration material. Increasing carbonation pressure accelerates the mineralization reaction of steel slag, and the optimal carbonation efficiency has been achieved at a pressure of 0.3 MPa with a carbon sequestration efficiency of up to 16.65%. However, excessively high pressures, such as 0.4 MPa, lead to overly dense specimen surfaces, hindering internal carbonation and reducing specimen strength. The analysis from MIP (mercury intrusion porosimetry) and SEM (Scanning Electron Microscopy) confirms that the products formed by carbonation fill the pores with diameters around 1 μm and significantly increase the fractal dimensions of seepage pores and transition pores. Carbon emission and benefit analysis indicate that carbon-negative materials can be produced under optimal CO2 conditions. In conclusion, this study reveals the intricate relationship between carbonation pressure, sustainability, and efficiency in microbial-assisted in situ mineral carbonation processes.