Research focus at the iBMB - Division of Building Materials

Aditive manufacturing for cement-based materials

Automated additive manufacturing such as 3D printing or robot-assisted spraying of concrete is finding its way into construction industry. A central task in the development of these technologies is the optimal setting of the concrete formulation parameters such as the type and amount of the binder as well as additives, grain size, water content and optionally choice and dosage of further additives for controlling the rheological and setting properties. The concrete formulations have to meet the requirements regarding strength, density, density gradients, surface quality, dimensional accuracy and subsequent machinability resulting from very different applications.

Rheology

The prerequisite for the development of additive manufacturing technologies such as 3D printing or robot-assisted spraying of cement-based materials is the understanding of rheological fundamentals such as the knowledge of the flow and deformation behaviour of multiscale cement-based materials. In the fresh state the cement-based materials are highly concentrated suspensions of predominantly inorganic particles in water. In addition to the wide range of particle sizes between about 100 nm and 30 μm and the high solids fraction up to 90% a specific feature of these suspensions is the reactivity of cement and other binders. The aim is to gain a basic understanding of the relevant processes that shape the rheological properties of fresh materials. The key to this is a detailed understanding of the energetic and mechanical interaction of reactive and nonreactive particles and the aqueous phase.

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(DBFL at ITE, Photo: ITE)

Computed tomography

Strength and durability of cement-based materials are strongly influenced by the heterogeneous structure of the material. For closer investigations, it is necessary to consider cement-based materials as heterogeneous material and to identify and characterize the reactive and non-reactive particles of the cementitious material. One of the most innovative technologies for detecting and describing the particle structure and for the characterization of the particles inside cementitious materials is computed tomography, which can produce a three-dimensional scan of the material and the particles with high precision.

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(CT-image segmentation, Figure: iBMB)