During this PhD project, Krestine Hofstedt Rasmussen investigated how stone wool fibers are able to withstand extremely high temperatures (~1100 °C) and provide effective fire protection. Stone wool is widely used as a fire-safe insulation material, yet the structural reasons for its high-temperature stability have long been unclear. Using a combination of advanced X-ray and electron microscopy-based techniques, the project revealed how the atomic structure of stone wool fibers changes during heating in air. The study showed how iron oxidation, atomic rearrangements, and the formation of nano- and microscale crystals gradually transform the original amorphous fibers into crystalline fibers. These changes occur in a highly ordered sequence, from surface crystallization to extensive bulk crystallization at higher temperatures.

The results establish a clear link between atomic-scale processes, crystal formation, and the macroscopic fire resistance of stone wool. This new understanding provides a scientific foundation for developing more durable, efficient, and sustainable stone wool insulation materials for future industrial applications.

The industrial PhD study was completed at the Interdisciplinary Nanoscience Center (iNANO), Faculty of Natural Sciences, Aarhus University in collaboration with the company ROCKWOOL A/S.

This summary was prepared by the PhD student.

Time: Monday the 9^th of March 2026, at 10:00-13:00
Place: Building 1170, room 347, Lecture Theatre AUD, Department of Biochemistry, Aarhus University, Ole Worms Allé 3, 8000 Aarhus.
Title of PhD thesis: From Macro to Atomic Scale: Insights into the Structural Behavior of Stone Wool Fibers upon Heating
Contact information: Krestine Hofstedt Rasmussen, e-mail: krra@inano.au.dk, tel.: +45 22227281.
Members of the assessment committee:
Professor Jan S. Pedersen (chair), iNANO, Aarhus University, Denmark.
Professor Paul A. Bingham, Sheffield Hallam University, United Kingdom.
Senior R&D Engineer Anna Katerinopoulou, Topsøe A/S, Denmark.
Main Supervisor:
Professor Dorthe B. Ravnsbæk, Department of Chemistry, Aarhus University, Denmark. *
Senior R&D Engineer Denis Okhrimenko, ROCKWOOL A/S, Denmark.
Co-supervisor:
Assistant Professor Espen D. Bøjesen, iNANO, Aarhus University, Denmark.
Senior R&D Engineer Louise Belmonte, ROCKWOOL A/S, Denmark.
Language: The PhD dissertation will be defended in English. The defence is public.
 

The PhD thesis is available for reading at the Graduate School of Natural Sciences/GSNS, Ny Munkegade 120, building 1521, 8000 Aarhus C.