Compressive Strength and Expansion Characteristics of Mortar Mixtures Incorporating Chronologically Aged-Basic BOFS Aggregates Blended with GGBFS and Fly Ash

During the steelmaking process, many by-products, such as blast-furnace slag (BFS), basic oxygen furnace slag (BOFS), and ladle slag (LS), are generated. Unlike BFS, utilizing BOFS is limited due to its expansive volumetric characteristics by the transformation process of free lime (f-CaO) and free magnesia (f-MgO) to portlandite (Ca(OH)2) and brucite (Mg(OH)2). The natural aging process may help BOFS used as an aggregate in mortar or concrete because harmful elements such as f-CaO and f-MgO could be consumed during this stage. This study evaluated compressive strength and expansion characteristics of mortar mixtures incorporating chronologically aged-BOFS aggregates blended with ground granulated blast furnace slag (GGBFS) and ASTM class F fly ash (FFA). Test results revealed that the longer aged BOFS aggregate, the lower compressive strength, regardless of mixture types. The aging process of BOFS aggregate reduced the expansion of mortar mixtures. Incorporating GGBFS or FFA into mortar mixtures containing BOFS aggregate even more reduced the expansion of the mixture.