Public defence in Civil Engineering, MSc. Fan Zhang

Title of the thesis: “Microwave healing and deicing of asphalt pavements containing industrial slags — Towards intelligent and sustainable road winter maintenance”

Thesis defender: Fan Zhang
Opponent: Prof. R. Christopher Williams, Iowa State University, USA
Custos: Prof. Weiwei Lin,Aalto University School of Engineering

In the cold and snowy Nordic regions, roads are exposed to harsh winter conditions that lead to early pavement cracking and dangerous ice formation. This doctoral research investigates how microwave heating (MH), an innovative and sustainable technology, can be used to enhance road durability by improving both self-healing and deicing performance of asphalt pavements. 

The study also explores the use of industrial waste materials—specifically steel slag—as a substitute for traditional road aggregates. These waste slags show excellent strength and microwave absorption properties, offering a way to make road surfaces both stronger and more energy-efficient during winter maintenance. The research evaluates how well asphalt pavements can heal themselves after cracking through repeated cycles of heating and cooling under different conditions. It also analyzes the magnetic and microwave properties of various waste slags to determine the most suitable material. By testing asphalt mixtures with different slag contents at various freezing temperatures and ice thicknesses, the study measures deicing performance, carbon emissions, and economic cost-benefit.

Key findings show that microwave heating can achieve over 80% healing efficiency under optimal conditions. Steel slag, in particular, demonstrates excellent microwave absorption at the frequency used (2.45 GHz), making it ideal for enhancing deicing performance. Although excessive slag can lead to uneven heating, moderate use significantly improves deicing efficiency compared to traditional pavements. Furthermore, steel slag asphalt pavements are cost-effective and produce comparable carbon emissions. The study also shows that polymer-modified binders withstand freeze-thaw cycles better than conventional ones, making them more suitable for MH applications.

This dissertation offers practical guidance for designing self-healing, deicing asphalt mixtures using recycled materials. The findings support more sustainable winter road maintenance, reduce reliance on non-renewable resources, and bring clear environmental and economic benefits.

Thesis available for public display 10 days prior to the defence at Aaltodoc. 

Contact information: fan.3.zhang@aalto.fi