Civil and Environmental Engineering - Master Calendar

View Full Calendar

PhD Final Defense for Yujia Lu

Event Type
Civil and Environmental Engineering
Newmark 3017
Apr 5, 2024   8:30 am  
Originating Calendar
CEE Seminars and Conferences

Multi-scale Studies of Aging, Rejuvenation, and Extrinsic Self-healing in Bituminous Materials

Advisor: Assistant Professor Ramez M. Hajj


Oxidative aging is a crucial factor that influences the performance of asphalt mixes in flexible

pavements. The aged asphalt mix is more susceptible to fatigue and thermal cracking, the most

critical distress at intermediate and low temperatures, respectively. An emerging technology to

mitigate the cracking of asphalt pavements is the use of self-healing capsules embedded in asphalt

mixtures. To better design self-healing capsules, it is imperative to understand the aging and

rejuvenation mechanisms from chemical, mechanical, and micro-surface structure changes of


Because aging happens to the asphalt binder region, the aging effect of asphalt binder was

investigated based on static surface topography and time-sensitive asphalt binder microstructure.

They were also correlated with a recently validated asphalt binder cracking test, the poker chip

test. When the dominant effect of virgin asphalt binder in blended asphalt binder was realized in

this dissertation, an optimal dosage determination method was developed based on the response

on long-term aging effect of rejuvenated asphalt. Based on the trend of dosing rejuvenators,

encapsulated rejuvenators were optimized from healing agent type, concentration, capsule shell

thickness, and capsule percentage perspectives. The capsules' applicable scenarios and potentials

were also expanded from the fine aggregate matrix (FAM) scale to the asphalt concrete (AC) scale.

Finally, the benefits of capsules compared to solely rejuvenating were explained.

In this dissertation, asphalt material characterization tools provided micro morphology damage

indicators, chemical analysis, and anti-cracking analysis methods based on the understanding of

extended aging. This dissertation also revealed that both optimum dosages and fundamental

mechanisms of rejuvenation were affected by rejuvenator type, base binder selection, recycled

material content, and the aging level of the binder. The prospect of self-healing asphalt was

explored. This research therefore established a framework for engineering a combination of

capsules for use at pavement scale based on an understanding of chemical interactions, mechanical

properties, and multiscale experimental verification.

link for robots only