Multi-scale insights into the adhesion of steel slag-asphalt interface influenced by hydration process

Document Type

Article

Publication Date

6-20-2025

Department

Department of Civil, Environmental, and Geospatial Engineering

Abstract

Steel slag, a byproduct of the steelmaking process, exhibits poor volumetric stability in its freshly produced or untreated state, which significantly restricts its application in pavement engineering. Currently, weathering is the predominant process for treating steel slag. A multi-scale approach was employed to investigate the mechanism of hydration reactions on the adhesion properties of the steel slag-asphalt interface during the weathering process in this study. The effects of hydration on adhesion properties were evaluated through modified boiling tests and surface free energy (SFE). The surface morphology of unhydrated and hydrated steel slag was compared using scanning electron microscopy (SEM) and optical profilometry. The adhesion properties of asphalt at the interfaces with unhydrated steel slag (C3S and C2S), hydrated steel slag (CaCO3), and basalt (SiO2) were systematically analyzed using molecular dynamics (MD) simulations, incorporating static, pull-off, and novel dynamic water scouring models to simulate diverse environmental conditions. The results indicated that the mass loss rate (MLR) and peeling rate (PR) of hydrated steel slag after a 10-minute boiling test were 1.3 and 2.2 times higher than those of unhydrated steel slag, respectively. Meanwhile, hydration treatment reduced the adhesion work between steel slag and asphalt by 2.0 % and increased the peeling work by 33.5 %. SEM images and 3D surface topography analyses showed that hydration transformed the rough-textured structure on the steel slag surface into a loose honeycomb structure, resulting in an increase of 6.42 % in arithmetic average roughness (Ra) and 8.84 % in root mean square roughness (Rq). MD simulations demonstrated that the mean square displacement (MSD), diffusion coefficient (DC), and z-value of relative concentration (RC) peaks of asphalt on the CaCO3 surface were greater than those on C3S and C2S, while the interface interaction energy, adhesion work, and cohesion ratio (CR) were lower. Under water molecule scouring, the simulated peeling rate (SPR) of asphalt on the CaCO3 surface increased by 34.5 % compared to C3S but decreased by 7.7 % compared to C2S. Furthermore, there was a strong correlation (r > 0.8) between the experimental and simulation data.

Publication Title

Construction and Building Materials

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