Document Type

Dissertation - Open Access

Award Date

2023

Degree Name

Doctor of Philosophy (PhD)

Department / School

Civil and Environmental Engineering

First Advisor

Rouzbeh Ghabchi

Keywords

Asphalt, Chloride salt, Moisture-induced damage, Multiscale Characterization, Winter maintenance

Abstract

More than 70% of the United States' roadway network is located in regions subjected to severe winters, resulting in icy pavements that pose safety risks. Winter maintenance operations involving chloride-based deicers such as NaCl, CaCl2, and MgCl2 are essential for ensuring the safety, mobility, and functionality of roads. However, these deicers can lead to diminished pavement durability due to moisture-induced damage. This study examined the effects of these deicers on adhesion evolution and moisture-induced damage mechanisms of asphalt binder-aggregate systems at the macro-, centi-, micro-, and nanoscales. Macro-scale performance characteristics of PG 58-34 hot mix asphalt (HMA) specimens, including rutting, moisture-induced damage, and fatigue resistance, subjected to different deicer solution freeze-thaw cycles, were evaluated. At the component level, the effect of aggregate mineralogy (granite, quartzite, and limestone), asphalt binder types (PG 58-34 and PG 64-34), deicer type (NaCl, CaCl2, and MgCl2), and freeze-thaw cycles on adhesion and damage mechanisms responsible for moisture-induced damage were assessed. At the micro-scale, a thermodynamic-based surface free energy method was pursued to characterize the adhesion and debonding energies as well as the moisture-induced damage potential of the binder-aggregate systems for different aggregates and asphalt binders in contact with various deicer solutions. In addition, atomic force microscopy (AFM) was used to investigate the impact of deicer type, concentration, and freeze-thaw cycles on the surface morphology and adhesion properties of the PG 64-34 asphalt binder. According to the findings of the study, elevated salt concentrations of deicer solutions led to a deterioration of adhesive and cohesive bonds between asphalt binder and aggregate systems in different scales. However, lower concentrations had an even greater damaging effect due to their high mobility, which allowed them to penetrate the asphalt binder's internal structure. This infiltration induced chemical aging and altered the asphalt binder's microstructure via salt erosion. The effects of this phenomenon were observed on multiple testing scales, and the results from the various testing scales corroborated one another, supporting the findings.

Publisher

South Dakota State University

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Rights Statement

In Copyright