Use of Basic Oxygen Furnace Slag (BOFS) in Superpave Mix Design: BOFS Aggregate Properties

Abstract

This research aims to evaluate the properties of basic oxygen furnace slag (BOFS) as aggregates used in Superior Performing Asphalt Pavements (Superpave) mix design. A total of five different aggregates, including one limestone and four BOFS aggregates with different ages, were evaluated by the following aggregate properties: specific gravity, water absorption, Los Angles abrasion, aggregate crushing value, angularity, flakiness, soundness (sulfate chemical and freeze-thaw resistance), and expansion characteristics. Then, the volume stability of the hot mix asphalt (HMA) mixture was also discussed based on the aging effect of BOFS aggregate. Test results indicated that aged BOFS aggregate performs better than unaged BOFS aggregate: Aged BOFS aggregate has lower water absorption, lower aggregate crushing value, higher abrasion resistance, and less expansion. The flakiness and angularity of BOFS aggregates were satisfied with Superpave criteria. However, if free-lime (f-CaO) and free magnesium (f-MgO) in BOFS aggregate exist, it may cause the volume stability of asphalt mixtures with BOFS aggregate. In conclusion, if BOFS is appropriately aged and weathered, BOFS can be an alternative to conventional aggregate.