Impact of basic oxygen furnace slag on the hydration microstructure, mechanical properties, and carbon emissions of supersulfated cement

Abstract

Supersulfated cement (SSC) is recognized as a cementitious material with low CO2 emissions, consisting predominantly of ground granulated blast-furnace slag (GGBS) and a minor activator content. The production of GGBS production constitutes the primary source of CO2 emissions in SSC. In contrast, carbon emissions from the production of basic oxygen furnace slag (BOFS) are lower, and BOFS inherently exhibits substantial carbonization potential. Therefore, in this study, BOFS is employed as a replacement for GGBS in formulating an innovative low-emissions binder denoted as BOFS-modified supersulfated cement (BMSC). This study investigates the influence patterns of BOFS substitution for GGBS on the strength properties of BMSC. Furthermore, a series of experiments involving QXRD, TGA, SEM, and MIP were conducted to systematically investigate the mechanistic impact of BOFS on the hydration microstructure of BMSC. The findings reveal that substituting 10 % of GGBS with BOFS contributes to an enhancement in both flexural and compressive strength of specimens at 7 and 28 days. BOFS exerts a positive influence on the formation of ettringite in BMSC. The C2S and C4AF within BOFS also demonstrate distinct hydration activity. Additionally, BOFS can reduce large pores in the early hydration paste and contribute to narrowing the average pore size. Moreover, the evaluation of the Global Warming Potential (GWP) demonstrates that the replacement of slag with BOFS can lead to a further reduction of up to 30 % in the carbon emissions of SSC.