Date of Award

Summer 2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Materials and Infrastructure Systems

First Advisor

Nazimuddin Wasiuddin

Abstract

Moisture damage is a major form of pavement distress that causes state and federal highways to undergo high maintenance cost (Bhasin, 2006). According to Hicks et al., (2003), in a survey conducted by the Colorado Department of Transportation, mainly including US agencies (1 Canadian Province), 82% of these agencies required the use of anti-strip treatment (additives) to avert moisture damage. Additionally, 87% of these agencies test for moisture susceptibility. Despite extensive research performed on the moisture damage mechanisms in flexible pavements, it has been a challenge to obtain one single test that can comprehensively quantify the damage and to also predict the material performance in the field (Caro et al., 2008; Solaimanian et al., 2003). In this study, the role of the dewetting mechanism in moisture damage of asphalt pavements was investigated. Three main asphalts, mainly two anti-strip additives, and a warm mix additive were utilized. Tests, such as Pull-off, Surface free energy, Modified boil and microscopic analysis of dewetting were performed. A unique dewetting-based moisture damage test procedure was developed consisting of a moisture conditioning procedure and quantitative analysis of the dewetting with the use of a microscope and NI Vision (2012) software. The dewetting analysis procedure includes measurements of the total dewetted area and number of dewetted holes. It was observed that the dewetting phenomenon occurs primarily under a trapped air bubble in the asphalt film submerged in water. Most of the dewetting pattern followed that of an exponential growth. Polymer (Styrene Butadiene Styrene) in PG 76-22M asphalt did aid in reducing dewetting. At high pH, 10, the Adhere LOF 6500 additive increased dewetting for all three asphalts. The critical film thickness can be defined as the minimum thickness above which very few dewetted holes was observed, which indicate a proposed threshold parameter for asphalt film thickness in the pavement mixes. The critical film thickness for all three asphalts was estimated experimentally and found to be 300 µm.

The findings of this study on understanding the role of dewetting on moisture damage in asphalt pavements will assist in the implementation of a unique dewettingbased moisture damage test procedure and analysis.

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