Annotated Summary

Ahmedzade, P., & Sengoz, B. (2009). Evaluation of steel slag coarse aggregate in hot mix asphalt concrete. Journal of hazardous materials, 165(1-3), 300-305. doi:10.1016/j.jhazmat.2008.09.105

This article focuses on the influences of the utilization of steel slag as a course aggregate on the properties of hot mix asphalt. Ahmedzade’s and Sengoz’s main aim of this article seems to be to convince readers of the great effects of substituting coarse and fine aggregates in asphalt mix with steel slag aggregates. Steel slag, a by-product of steel making has been utilized in a number of applications in the civil engineering industry. For paving mixes, steel slag should be limited to only replace either the fine or coarse aggregate fraction, but not both. Steel slag has an angular shape, and for this reason, hot mix asphalt containing 100% steel slag is susceptible to high void space and bulking problems and will also be prone to over-asphalting during production and subsequent flushing due to in-service traffic compaction. In this study, four different asphalt mixtures containing two types of asphalt cement (AC-5 & AC-10) and course aggregate (limestone & steel slag) were used to prepare Marshall specimens and to determine optimum bitumen content. The limestone aggregate was procured from quarries around Elazig while the steel slag was directly obtained from Erdemir Steel Manufacturing Factory. Different tests were conducted to evaluate the mechanical characteristics of all mixtures. Such tests were Marshall stability, flow and Marshall quotient, indirect tensile stiffness modulus, creep stiffness, indirect tensile strength and resistance to moisture damage. Electrical resistivity of the specimens was also measured on Marshall specimens by electrical resistivity testing apparatus and in accordance with ASTMD257-91. Scanning electron microscope was used to observe the surface texture of steel slag and limestone where it was seen that plenty of pores were on the surface steel slag which implies that steel slag is a kind of porous material. From the results obtained from the different tests conducted, it was observed that steel slag used as a course aggregate improved the mechanical properties of asphalt mixtures. The results indicated that steel slag mixtures have excellent engineering properties and good electrical conductivity. AC-10/SS asphalt mixture showed the best performance among the tested mixtures. Moreover, the volume resistivity values showed that steel slag electrical conductivity were better than that of limestone mixtures.