Research
Mission statement
The unifying theme in the research of Physical Chemistry of Building Materials revolves around the colloidal and surface chemistry of construction materials both on a fundamental and applied level, particularly the interaction of organic chemical admixtures with inorganic surfaces. Through modification of different interfaces, large effects can be observed with relatively small amounts of material, and important properties such as strength and durability can be altered to produce more sustainable construction materials.
The research of the chair falls under three main categories:
Complex processes, such as cement hydration, can be better understood when the interactions with chemical admixtures on the molecular level can be better characterized and quantified. This type of understanding can directly contribute to advanced construction processes such as 3D printing with concrete, through their incorporation in processes that are now being developed within research that falls under the umbrella of the group. Finally, conservation of the built cultural heritage can best be performed through an understanding and diagnosis of the degradation mechanisms that impact them.
Admixtures and cement hydration
Reducing CO2 emissions related to cement production is a major objective for the construction sector. In this respect the most widely applicable solutions involve the use of blended cements. Our contributions to this active field of research involve molecular level insights into how aluminate ions from supplementary cementitious materials can passivate the hydration of tri-calcium silicate the main reactive phase in ordinary clinker. Additionally, we have promising results for the production of a low clinker cement (50%) to be used as main cement on the Swiss market.
Modern concrete makes ample use of chemical admixtures, in particular superplasticizers for rheology control. The most used of these are polycarboxylate ether (PCE) that can strongly delay cement hydration processes, which is a growing problem for low clinker cements. Recent work from our group demonstrates the relationship between molecular parameters and the delay in cement hydration induced by PCEs. Importantly, it opens a new pathway for molecular design to resolve this issue. An understanding of how flow loss occurs during the early stages of cement hydration has also been more clearly defined. This link between rheology and the dynamic process of cement hydration isone of the enduring mysteries in cement science.
Digital fabrication
Digital fabrication in construction is a newly established field, in which we have become very active, thanks our pioneering colleagues Profs. Gramazio & Kohler. Our own work began with Smart dynamic casting and has expanded to a variety of digital controlled processes requiring novel material chemistry solutions. We are in particular active members of the external page Swiss National Centre for Competence in Research for Digital Fabrication in Architecture.
Key research highlights include the development of chemical admixture-based set on demand processing systems for cementitious materials, and development of new measurement techniques essential for enabling process success. Perhaps the foremost research highlight is the external page dfab House, in which PCBM was involved in multiple projects such as the external page Mesh Mould wall (a Swiss Technology Award 2016 winner, and Concrete Innovation Conference winner), the external page Smart Dynamic Casting façade mullions, and the aerogel membrane panels.
Heritage science
The conservation of built cultural heritage is a field that calls for novel scientific solutions, and we are specifically interested in the case of stone monuments. In this regard, we study weathering mechanisms with the aim of developing effective and durable methods of treatment and repair. An important effort of ours consists in identifying, through utilization of new monitoring tools and rare events analysis, the events responsible for damage. This allows us to reproduce those events in the laboratory as a way to accelerate degradation, while not changing the mechanism responsible for it.