The Group
The chair for Physical Chemistry of Building Materials belongs to the Institute of Building Materials of the Department of Civil, Environmental and Geomatic Engineering. The main mission of the institute consists in teaching and research on construction materials.
In terms of teaching we believe that it is our responsibility to prepare civil engineers to increasingly endorse responsibility for the durability of the structures they will be designing as well for the environmental impact of the materials they prescribe. Because building materials must evolve to minimize their environmental impact, practising civil engineers will, during their careers, be confronted to materials with new or modified properties. To best prepare them for this, it is essential to transmit the materials science principles that will allow them to ask the right questions and judge the quality of the responses they get. Our teaching strives to reach this objective without neglecting today’s reality.
In terms of research, we focus on the physical chemistry aspects of construction materials, as well as their processing and in particular digital fabrication. This offers a great range of possibilities to modify macroscopic properties with only minor modifications to the material bulk composition. The material mainly investigated is concrete, although gypsum, brick and stone can also be included.
General vision for research in construction materials
Concrete represents the largest volumes of material used by man and is irreplaceable for innumerable large infrastructures. From a point of view of natural resources, ecology and economy, it is virtually not possible to imagine substituting it by any other material. Because of this, volumes used are colossal. As a result, the production of Portland cement, the main binder of concrete, contributes 5-7% of all man made CO2. This is mainly due to the limestone decarbonation, which is essential to the chemistry of this mineral binder.
Society therefore faces the challenge of reducing the environmental impact of concrete without compromising people’s need for housing and infrastructure. The possible solutions are largely known and involve:
- Partial cement (clinker) replacement by supplementary cementious materials
- Broader use of concrete mix designs that limit cement content
- Enhancement of durability (designing new infrastructures for longer service life)
- Rehabilitation of existing infrastructures (extending the service life of existing infrastructures)
- Structurally optimized design allowing for reduced material use
These are the only solutions that have a real potential of having a large scale impact in this sector. However, within these options, each approach must remain realistic in terms of large scale feasibility.
To achieve this, any solution must be relatively robust to material variations whether geographical, temporal and/or seasonal. In practice, a given solution will almost always require some degree of local adaptation, as a change in mix design, cement or admixture formulation. For reasons of cost effectiveness, these adaptations must be identifiable with as little work as possible. Performance predictability is therefore an area of real practical interest and one to which academic research can contribute important building blocks. In this area, research must identify and quantify the impact of the main parameters that control performance, as well as their mutual interactions.
The need for robustness mentioned above concerns rheology (ex: placing), strength development (ex: demolding time) and durability (ex: service life). All these properties can be strongly influenced, either directly or indirectly, by the use of chemical admixtures. Such additives produce large effects when added only in small amounts. Consequently, the environmental impact of concrete can be improved with only little effort. For instance, the mixture proportions of concrete can be modified to reduce the cement content and chemical admixtures could be used in conjunction to compensate for strength loss by making it possible to use less water without compromising flow.
Today, chemical admixtures already play an important role in reducing the environmental impact of concrete and this can only be expected to increase in the future. There is therefore a real need to deepen the existing knowledge on the mechanisms by which these products work in order to use them efficiently in the systems of growing complexity that will be used in the years to come.
This subject is a central interest in the Chair for Physical Chemistry of Construction Materials. It is one that has brought us into the field of digital fabrication, where our expertise on rheology and hydration control found novel applications. In this field, an important hope is to increase the cost-effectiveness of structurally optimized shapes, which paradoxically reduce material consumption, but are too expensive to produce with standard processes.