High-gravity carbonation of basic oxygen furnace slag for CO2 fixation and utilization in blended cement

This study explores the feasibility of developing carbon dioxide (CO2) fixation and utilization as supplementary cementitious materials (SCMs) using basic oxygen furnace slag (BOFS) through a high-gravity carbonation process. The developed process is considered as a cleaner approach, compared to convention treatment processes in steelmaking industry, to simultaneous reduction of CO2 emission and stabilization of BOFS. The carbonated BOFS can be used as SCMs in blended cement. First, the CO2 fixation capacity of BOFS was quantified by thermo-gravimetric analysis in this study. The kinetics of the high gravity carbonation process were also determined using a surface coverage model. The results indicated that up to 215 g of CO2 was fixed per kg of BOFS through high-gravity carbonation for 3 h at 60 degrees C. In addition, engineering properties and hydration characteristics of blended cement with 10% fresh or 10% carbonated BOFS as SCMs were investigated. Cement blended with 10 wt% of carbonated BOFS resulted in reduced setting times and accelerated early strength development, which was consistent with the hydration heat releases and X-ray diffraction analyses. The observations of scanning electron microscope suggest that the carbonated BOFS serve as nuclei for the precipitation of hydration products, thereby accelerating the hydration. It is also noted that the properties of blended cement using carbonated BOFS met ASTM requirements for setting time, compressive strength, autoclave expansion, and sulfate resistance. Furthermore, costs and benefits of the high-gravity carbonation for CO2 fixation and BOFS utilization were estimated. (C) 2016 Elsevier Ltd. All rights reserved.