Performance investigation and optimization of the granulation-CO2 concentration for the production of high-strength BOFS aggregates.

Studies have demonstrated that basic oxygen furnace slag (BOFS) powder can be granulated to produce a strong artificial aggregate through strengthening with accelerated carbonation. However, our previous results showed that a 100% CO 2 concentration applied during granulation could significantly degrade the properties of the produced BOFS aggregate due to the loss of bridging water upon undergoing a rapid exothermic reaction. Therefore, this paper aims to optimize the CO 2 concentration during granulation of BOFS and investigate the impact on the subsequent post air or CO 2 curing of the produced aggregates. According to X-ray computed tomography results, the CO 2 applied during granulation should be controlled at 40 vol% or less in order to provide proper connective pores in freshly granulated BOFS aggregates for subsequent carbonation, thereby allowing higher CO 2 uptake and better mechanical development of hardened BOFS aggregates. It was also noted that with a high granulation-CO 2 concentration typically of 100% can result in the formation of multiple granules in a single produced BOFS aggregate, hence lowering the intrinsic structure and aggregate strength. Compared to the CO 2 reaction that occurs during granulation, post CO 2 curing plays the main role in developing the mechanical strength of hardened BOFS aggregates. [Display omitted] • Optimization of CO 2 concentration during granulation of BOFS was studied. • Synchronized carbonation-granulation can control connective pores for carbonation. • High granulation-CO 2 concentration formed multiple granules in a single aggregate. • Post CO 2 curing played an important key to contribute the final strength. • It is economically feasible to produce high strength lightweight BOFS aggregate. [ABSTRACT FROM AUTHOR]