Use of hydrated ladle furnace slag as a filler substitute in asphalt mastics: rheological analysis of filler/bitumen interaction

Abstract

The increase in industrial activity and societal demand has made the reuse and recovery of industrial waste and by-products a topic of global importance. New technologies focused on the reuse of these materials open up the possibility of promoting a sustainable circular economy in the industrial sector. Ladle furnace slag (LFS) is an industrial waste generated during steel refining, through a process of deoxidation and desulfurization of the material while it is in a liquid state in its second refining stage. This process generates large quantities of LFS without being used on a large scale, and most of it is destined for stockpile fields, producing an environmental and economic impact. The present research is based on the incorporation of Hydrated Ladle Furnace Slag (LFSh) into asphalt mastics to evaluate its viscoelastic behaviour using the Dynamic Shear Rheometer test (DSR-test). The incorporation of this industrial by-product generates an increased stiffness of the asphalt mastic, compared to a conventional mastic made with limestone. This increase in stiffness is greater in large dosages of LFSh filler, causing an inferior performance to limestone mastic at low temperatures in relation to what was demonstrated in the Linear Amplitude Sweep test (LAS) and Binder Yield Energy Test (BYET). The results obtained in the Multiple Stress Creep Recovery test (MSCR) show that the incorporation of LFSh filler is appropriate for warm conditions. Furthermore, the filler/bitumen ratio of 0,75 provides an increase in recoverability (R) of 24.17% over limestone mastic asphalt at a temperature of 70º C and a load of 3.2 kPa, and a significant loss of lower integrity at low temperatures (25º C).