Activation of BOF Slag with Dipotassium Hydrogen Phosphate: Enhancing Hydration, Carbonation Resistance, and Heavy Metal Leaching

Abstract

This study investigates the hydration of basic oxygen furnace (BOF) slag activated by dipotassium hydrogen phosphate (DKP) up to 3 wt.%. The findings reveal that DKP-activated BOF slag pastes exhibit improved strength, leaching behavior, and carbonation resistance. DKP-activated BOF slag pastes facilitate the completion of the main exothermic reaction within 3 days. Increasing DKP from 1 to 3 wt.% extends the induction period while enhancing overall hydration heat. This is attributed to the consumption of C₂S and brownmillerite, and the formation of hydrogarnet, C-S-H gel, and layered double hydroxides (LDHs). Concomitantly, porosity reduces from 40.73 to 22.36%, leading to significant strength gaining from 1.9 to 42.5 MPa over 28 days. Moreover, DKP-containing samples exhibit satisfactory carbonation resistance and limited heavy metal leaching, complying with the Dutch Soil Quality Decree (SQD). The study highlights the potential of phosphate activation to enhance the durability and environmental performance of BOF slag-based materials.