Design of asphalt mixes with steel slag aggregates using the Bailey method of gradation selection

Abstract

It has been reported in the literature that the asphalt mixes containing a high percentage of Steel Slag Aggregates (SSA) are susceptible to high void space. This is one of the major reasons that SSA usage is limited to replacement of either the fine or coarse aggregates fraction, but not both by the road agencies. More void spaces in the asphalt mixes with a higher proportion of SSA can be attributed to the high specific gravity of the coarse aggregate (CA) of SSA and the adoption of weight-based gradation selection for mix design. This issue can be addressed by adopting the volume-based Bailey method. The present paper attempts to provide a framework to design asphalt mixes with a high proportion (up to 100%) SSA with aggregate fractions of varying specific gravity by employing the Bailey method of gradation selection. The study in the paper showed that by adopting the Bailey method for gradation selection, SSA mixes with Voids in Mineral Aggregates (VMA) similar to Natural Aggregate (NA) mixes can be produced despite the significant differences in specific gravities between the fine and coarse aggregate fractions. Test for mechanical properties on asphalt mixes suggested that the resilient modulus of SSA asphalt mixes can be 1.4 to 1.8 times that of NA asphalt mixes. Owing to the high particle strength of SSA combined with the predominantly cubical shape, SSA mixes were found to be relatively more resistant to rutting. Comparisons based on linear elastic analysis and design of hypothetical pavement sections indicate that the fatigue life of pavement with SSA asphalt base layers is comparable with the fatigue life of the pavement with NA asphalt mix bases. It was also observed that the asphalt mixes with SSA aggregates had shown relatively more resistance to the moisture damage.