The department Civil and Mechanical Engineering of EMPA focuses on the development and the assessment of materials, systems and processes which lead to a decrease in the consumption of resources since the overall consumption of energy and raw materials in our society is highly determined by the construction and the operation of the built environment.
Durability and Safety
Premature failure of materials and systems is prohibited by the systematic characterization of their behaviour over time. One example is the development of structural health monitoring systems for civil infrastructures with a focus on online collection and processing of data delivered by various sensor systems. Composite materials such as carbon fibre reinforced polymers (CFRP) are used for the post-strengthening of existing structures in order to adapt them to enhanced static and dynamic loads. Service life prediction models are developed for materials and systems based on the realistic determination of the environmental parameters relevant for their ageing process and on a profound understanding of the associated physical and chemical processes. The expected durability of new materials and systems is determined by tailor made accelerated laboratory tests which lead to realistic deterioration processes. Failure analysis and expertises for public authorities is an important part of the services provided by the department.
The combination of smart materials, sensor technology, miniaturized electronics and sound engineering knowledge allow the creation of new solutions in a variety of areas. The use of light weight structures in structural engineering which i.e. would permit the construction of bridges with a wider span which is limited by their increased susceptibility to vibrations caused by ambient factors such as wind, rain or traffic. Therefore, a cable-stayed bridge was constructed which serves as a research platform for different projects such as the comparison of different controlled damping devices for the mitigation of cable vibrations. Another area of activity is the use of electroactive polymers which are of great interest due to their large deformation of 10% to 100% upon activation. First prototypes of devices are constructed with the aim to use them on a mid-term range as artificial muscles, active protheses or for the activation of large surfaces of shallow structures. In all areas, the experimental work is always accompanied by intensive modeling.
Consumption of energy and other resources
New solutions are needed to reduce the energy consumption of buildings. Renewable energy and increased energy efficiency in new buildings and especially in retrofitted buildings are among the top priorities. Examples are the development of vacuum insulation panels with a thickness of only 1-2 cm or thermally activated ceiling panels for retrofitting. Methods and concepts are developed which can be used to evaluate whether a new material, system or process fulfills the criteria of sustainability. One of them is the ecoinvent database which was developed in collaboration with other federal research institutes and which can be accessed over the internet. Furthermore, the use of recycled materials for the substitution of primary materials is supported by several research projects, mainly in the area of bituminous and cement-bound materials.
The macroscopic behavior of construction materials can only be fully understood and optimally tailored for a specific application if their behavior on a microscopic and even nanoscopic level is understood as well. New analytical tools such as AFM, FIB and others are used together with the modeling of the thermodynamics to gain new insights in the hydration of cement-bound materials. Based on these results it is possible to get a new approach to questions such as durability of concrete or the function of admixtures. The use of wood, the most important renewable material on national and world-wide scale, is supported by the improvement of the technical, ecological and economical quality of wood, wood based products and systems. A fascinating example is the extraction of cellulose fibrils out of wood with a diameter of only a few nm and length of several *m which can be used as polymer reinforcement, preferably in combination with a biodegradable polymer.