Investigation of microstructure and mechanical performance of carbon-capture binder using AOD stainless steel slag

The gamma-C2S that constitutes stainless-steel argon oxygen decarburization (AOD) slag is known to generate calcite and silicate gel through reaction with CO2 In this study, the mechanical performance and microstructure characteristics of cementitious materials that contained AOD slag were investigated with respect to carbonation. AOD slag that contained 38.1% gamma-C2S was used. It was crushed into two different finenesses; and paste specimens were prepared, in which up to 60% of ordinary Portland cement (OPC) was replaced by AOD slag. The specimens were cured in environments with CO2 concentrations of 0%, 5%, 10%, and 15%, to analyze the influence of the CO2 concentration. The compressive strengths were measured for the evaluation of the mechanical performances; and the pore size distributions were measured using a mercury intrusion penetrometer, to examine microstructural changes. Thermogravimetry/ derivative thermogravimetry (TG-DTG) analyses were employed for the measurement of the CO2 uptake, and the influences of the CO2 uptake on the compressive strength and microstructure were analyzed. In the non-CO2 curing environment, the compressive strength decreased and the number of pores increased as the substitution rate of the AOD slag increased. However, when the CO2 concentration increased, the specimen with AOD slag exhibited a decrease in the porosity and increase in strength. The influence of the fineness of the AOD slag was significantly different when the substitution rate was 30%, and non-significant when it was 60%. (C) 2020 Elsevier Ltd. All rights reserved.