Feasibility assessment of the use of basic oxygen furnace slag in open graded asphalt courses

Abstract

India is the world’s third largest steel producer with a production of 97.8 million tonnes in 2017. Steel slag is obtained as a by-product from steel-making industries during the conversion of iron to steel. Steel slag possesses favorable angularity and strength properties. This study aims to utilize basic oxygen furnace (BOF) steel slag as coarse aggregate for open graded asphalt courses (OGACs). OGAC is a special hot-mix asphalt wearing course that is designed for higher air voids to achieve quick drainage of surface water and better wet weather performance. High air voids in OGAC are created with the use of a higher proportion of uniformly graded coarse aggregates and low amount of fines. In this study, use of BOF slag in OGAC mixes is evaluated through 0% (control mix), 25%, 50%, 75% and 100% replacement of coarse natural aggregate. Further, two types of modified asphalt binders are used: polymer-modified and crumb rubber-modified binder for evaluation of OGAC mixes with and without BOF slag. OGAC mixes are evaluated for volumetric characteristics (bulk density and air voids), stone-on-stone contact, binder draindown, and raveling resistance. Raveling resistance is evaluated through Cantabro abrasion loss test under both unaged and aged conditions. Results of the study indicate that an increase in steel slag content enhances the stone-on-stone contact and improves the resistance to raveling of OGAC mixes. Based on statistical analysis through analysis of variance (ANOVA), binder content and slag replacement percentage are found to have significant influence on the properties of OGAC mixes.