A Laboratory Study on Basic Oxygen Furnace Slag and Granulated Blast Furnace Slag Mixtures

In Australia, a substantial quantity of metallurgical by-products, known as slag, is produced yearly, with the majority of slag generated from iron and steel-making industries. Common types of slag include blast furnace slag (BFS), granulated blast furnace slag (GBFS), and basic oxygen furnace slag (BOFS) (also known as steel slag). The BFS and GBFS have been successfully used in many engineering applications. However, fine BOFS (particle size <6 mm) has limited engineering applications due to the high percentages of free lime and magnesium oxide, which have a high potential to swell. This research focusses on stabilising BOFS using GBFS, a pozzolanic material. A detailed study was performed to understand the index properties, shear and swell behaviour for the selected blends of BOFS–GBFS. The BOFS and GBFS samples procured from the site were classified as well-graded sandy soil with gravel and poorly graded sand, and the results from the accelerated swell tests indicate that swelling in BOFS was reduced exponentially from 2.56 to 0.23% by adding 50% GBFS to BOFS. However, the peak deviatoric stress was decreased with an increased GBFS content. For instance, the peak friction angle \(({\text{\o}}_{{{\text{peak}}}}^{\prime} )\) was reduced to almost 40% for the blend with 50% GBFS. The optimal ratio of GBFS to BOFS for the road base application was identified between 25 and 30%, with swelling <1% and peak friction angle >43°.